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Sökning: L773:1477 9234 > (2010-2014)

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1.
  • Abbasi, Alireza, et al. (författare)
  • Ambidentate coordination of dimethyl sulfoxide in rhodium(III) complexes
  • 2011
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 40:5, s. 1111-1118
  • Tidskriftsartikel (refereegranskat)abstract
    • The two dimethyl sulfoxide solvated rhodium(III) compounds, [Rh(dmso-kappa O)(5)(dmso-kappa S)](CF(3)SO(3))(3) (1 & 1* at 298 K and 100 K, respectively) and [Rh(dmso-kappa O)(3)(dmso-kappa S)(2)Cl](CF(3)SO(3))(2) (2), crystallize with orthorhombic unit cells in the space group Pna2(1) (No. 33), Z = 4. In the [Rh(dmso)(6)](3+) complex with slightly distorted octahedral coordination geometry, the Rh-O bond distance is significantly longer with O trans to S, 2.143(6) angstrom (1) and 2.100(6) angstrom (1*), than the mean Rh-O bond distance with O trans to O, 2.019 angstrom (1) and 2.043 angstrom (1*). In the [RhCl(dmso)(5)](3+) complex, the mean Rh-O bond distance with O trans to S, 2.083 angstrom, is slightly longer than that for O trans to Cl, 2.067(4) angstrom, which is consistent with the trans influence DMSO-kappa S > Cl > DMSO-kappa O of the opposite ligands. Raman and IR absorption spectra were recorded and analyzed and a complete assignment of the vibrational bands was achieved with support by force field calculations. An increase in the Rh-O stretching vibrational frequency corresponded to a decreasing trans-influence from the opposite ligand. The Rh-O force constants obtained were correlated with the Rh-O bond lengths, also including previously obtained values for other M(dmso)(6)(3+) complexes with trivalent metal ions. An almost linear correlation was obtained for the MO stretching force constants vs. the reciprocal square of the MO bond lengths. The results show that the metal ion-oxygen bonding of dimethyl sulfoxide ligands is electrostatically dominated in those complexes and that the stretching force constants provide a useful measure of the relative trans-influence of the opposite ligands in hexa-coordinated Rh(III)-complexes.
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2.
  • Abbasi, Alireza, et al. (författare)
  • Potassium ion-mediated non-covalent bonded coordination polymers
  • 2012
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41:3, s. 850-859
  • Tidskriftsartikel (refereegranskat)abstract
    • Crystal structures and vibrational spectra of three related network-forming coordination complexes have been studied. Two novel thermodynamically stable pseudo-polymorphic solvated rhodium chloro compounds, [cis-RhCl4(DMSO-kappa S)(2)K](n), 1, and [cis-RhCl4(DMSO-kappa S)(2)K center dot 3H(2)O](n), 2, and one metastable compound [trans-RhCl4(DMSO-kappa S)(2)K center dot 0.25H(2)O](n), 3, crystallize at ambient temperature in the orthorhombic space group P2(1)2(1)2(1) for 1, and the monoclinic space groups P2(1)/n and P2(1)/c for 2 and 3, respectively. All three structures contain [RhCl4(DMSO-kappa S)(2)]-complexes in which the rhodium(III) ions bind to two dimethyl sulfoxide (DMSO) sulfur atoms and four chloride ions in distorted octahedral coordination geometries. The complexes are connected in networks via potassium ions interacting with the Cl- and the DMSO oxygen atoms. As the sum of Shannon ionic radii of K+ and Cl- exceeds the K-Cl distances in compounds under study, these compounds can be described as Rh-Cl-K coordination polymers with non-covalent bonding, which is not common in these systems, forming 1- and 2-D networks for 1/2 and 3, respectively. The 2-D network with nano-layered sheets for compound 3 was also confirmed by TEM images. Further evaluation of the bonding in the cis- and trans-[RhCl4(DMSO-kappa S)(2)](-) entities was obtained by recording Raman and FT-IR absorption spectra and assigning the vibrational frequencies with the support of force-field calculations. The force field study of complexes reveals the strong domination of trans-effect (DMSO-kappa S > Cl) over the effect of non-covalent bonding in coordination polymeric structures. The comparison of calculated RhCl, RhS and SO stretching force constants showed evidence of K+-ligand interactions whereas direct experimental evidences of K+-Cl- interaction were not obtained because of strong overlap of the corresponding spectral region with that where lattice modes and Rh-ligand bendings appear.
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3.
  • Agarwala, Hemlata (författare)
  • Bidirectional non-​innocence of the β-​diketonato ligand 9-​oxidophenalenone (L-​) in [Ru([9]​aneS3)​(L)​(dmso)​]​n, [9]​aneS3 = 1,​4,​7-​trithiacyclononane
  • 2014
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43, s. 3939-3948
  • Tidskriftsartikel (refereegranskat)abstract
    • The new compound [RuII([9]aneS3)(L)(dmso)]ClO4 ([1]ClO4) ([9]aneS3 = 1,4,7-trithiacyclononane, HL =9-hydroxyphenalenone, dmso = dimethylsulfoxide) has been structurally characterised to reveal almostequal C–O bond distances of coordinated L−, suggesting a delocalised bonding situation of the β-diketonatoligand. The dmso ligand is coordinated via the sulfur atom in the native (1+) and reduced states(1 and 1−) as has been revealed by X-ray crystallography and by DFT calculations. Cyclic voltammetry of1+ exhibits two close-lying one-electron oxidation waves at 0.77 V and 0.94 V, and two similarly closeone-electron reduction processes at −1.43 V and −1.56 V versus SCE in CH2Cl2. The electronic structuresof 1n in the accessible redox states have been analysed via experiments (EPR and UV-vis-NIR spectroelectrochemistry)and by DFT/TD-DFT calculations, revealing the potential for bidirectional non-innocent behaviourof coordinated L•/−/•2−. Specifically, the studies establish significant involvement of L basedfrontier orbitals in both the oxidation and reduction processes: [([9]aneS3)(dmso)RuIII–L•]3+ (13+) ⇌ [([9]-aneS3)(dmso)RuIII–L−]2+/[([9]aneS3)(dmso)RuII–L•]2+ (12+) ⇌ [([9]aneS3)(dmso)RuII–L−]+ (1+) ⇌ [([9]aneS3)-(dmso)RuII–L•2−] (1) ⇌ [([9]aneS3)(dmso)RuII–L3−]−/[([9]aneS3)(dmso)RuI–L•2−]− (1−).
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4.
  • Agarwala, Hemlata (författare)
  • Electronic structure and catalytic aspects of [Ru(tpm)​(bqdi)​(Cl​/H2O)​]​n, tpm = tris(1-​pyrazolyl)​methane and bqdi = o-​benzoquinonediimine
  • 2013
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 42, s. 3721-3734
  • Tidskriftsartikel (refereegranskat)abstract
    • The diamagnetic complexes [Ru(tpm)(bqdi)(Cl)]ClO4 ([1]ClO4) (tpm = tris(1-pyrazolyl)methane, bqdi =o-benzoquinonediimine) and [Ru(tpm)(bqdi)(H2O)](ClO4)2 ([2](ClO4)2) have been synthesized. Thevalence state-sensitive bond distances of coordinated bqdi [C–N: 1.311(5)/1.322(5) Å in [1]ClO4;1.316(7)/1.314(7) Å in molecule A and 1.315(6)/1.299(7) Å in molecule B of [2](ClO4)2] imply its fullyoxidised quinonediimine (bqdi0) character. DFT calculations of 1+ confirm the {RuII–bqdi0} versus the antiferromagneticallycoupled {RuIII–bqdi˙−} alternative. The 1H NMR spectra of [1]ClO4 in different solventsshow variations in chemical shift positions of the NH (bqdi) and CH (tpm) proton resonances due to theirdifferent degrees of acidity in different solvents. In CH3CN/0.1 mol dm−3 Et4NClO4, [1]ClO4 undergoesone reversible RuII ⇌ RuIII oxidation and two reductions, the reversible first electron uptake being bqdibased (bqdi0/bqdi˙−). The electrogenerated paramagnetic species {RuIII–bqdi0}(12+) and {RuII–Q˙−}(1)exhibit RuIII-type (12+: = 2.211/Δg = 0.580) and radical-type (1: g = 1.988) EPR signals, respectively, asis confirmed by calculated spin densities (Ru: 0.767 in 12+, bqdi: 0.857 in 1). The aqua complex [2](ClO4)2exhibits two one-electron oxidations at pH = 7, suggesting the formation of {RuIVvO} species. The electronicspectral features of 1n (n = charge associated with the different redox states of the chloro complex:2+, 1+, 0) in CH3CN and of 22+ in H2O have been interpreted based on the TD-DFT calculations. The applicationpotential of the aqua complex 22+ as a pre-catalyst towards the epoxidation of olefins has beenexplored in the presence of the sacrificial oxidant PhI(OAc)2 in CH2Cl2 at 298 K, showing the desiredselectivity with a wide variety of alkenes. DFT calculations based on styrene as the model substratepredict that the epoxidation reaction proceeds through a concerted transition state pathway.IntroductionThe well recognized mixing of ruthenium dπ orbitals andπ orbitals of redox non-innocent quinonoid moieties introducesseveral manifestations with respect to the valence distributionat the metal–quinonoid interface, as depicted in Scheme 1.1This makes the electronic structure of such complexes sensitiveto the molecular frameworks, and in many occasions theexperimental results
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5.
  • Agarwala, Hemlata (författare)
  • Electronic structures and selective fluoride sensingfeatures of Os(bpy)2(HL2−) and [{Os(bpy)2}2(μ-HL2−)]2+(H3L: 5-(1H-benzo[d]imidazol-2-yl)-1H-imidazole-4-carboxylic acid)
  • 2014
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43, s. 13932-13947
  • Tidskriftsartikel (refereegranskat)abstract
    • The article deals with the newly designed mononuclear and asymmetric dinuclear osmium(II) complexesOsII(bpy)2(HL2−) (1) and [(bpy)2OsII(μ-HL2−)OsII(bpy)2](Cl)2 ([2](Cl)2)/[(bpy)2OsII(μ-HL2−)OsII(bpy)2](ClO4)2([2](ClO4)2), respectively, (H3L = 5-(1H-benzo[d]imidazol-2-yl)-1H-imidazole-4-carboxylic acid and bpy = 2,2’-bipyridine). The identity of 1 has been established by its single crystal X-ray structure. The ligand (HL2−)-basedprimary oxidation process (E°298, 0.23 V versus SCE) along with the partial metal contribution (∼20%) in 1 hasbeen revealed by the ligand-dominated HOMO of 1 (HL2−: 88%, Os: 8%), as well as by the Mulliken spindensity distribution of 1+ (HL2−: 0.878, Os: 0.220). Accordingly, 1+ exhibits a free radical type EPR at 77 K witha partial metal-based anisotropic feature (g1 = 2.127, g2 = 2.096, g3 = 2.046; = 2.089; Δg = 0.08).1H-NMR of the dinuclear 22+ in CDCl3 suggests an intimate mixture of two diastereomeric forms in a 1 : 1ratio. The DFT-supported predominantly Os(II)/Os(III)-based couples of asymmetric 22+ at 0.24 V and 0.50 Vversus SCE result in a comproportionation constant (Kc) value of 8.2 × 104. The class I mixed valent state of23+ (S = 1/2) has, however, been corroborated by the Mulliken spin density distribution of Os1: 0.887, Os2:0.005, HL2−: 0.117, as well as by the absence of a low-energy IVCT (intervalence charge transfer) band in thenear-IR region (up to 2000 nm). The appreciable spin accumulation on the bridge in 23+ or 24+ (S = 1, Os1:0.915, Os2: 0.811 and HL2−: 0.275) implies a mixed electronic structural form of [(bpy)2OsIII(μ-HL2−)-OsII(bpy)2]3+(major)/[(bpy)2OsII(μ-HL•−)OsII(bpy)2]3+(minor) or [(bpy)2OsIII(μ-HL2−)OsIII(bpy)2]4+(major)/[(bpy)2-OsIII(μ-HL•−)OsII(bpy)2]4+ (minor), respectively. The mixed valent {OsIII(μ-HL2−)OsII} state in 23+, however, fails toshow EPR at 77 K due to the rapid spin relaxation process. The DFT-supported bpy-based two reductions forboth 1+ and 22+ appear in the potential range of −1.5 V to −1.8 V versus SCE. The electronic transitions in 1nand 2n are assigned by the TD-DFT calculations. Furthermore, the potential anion sensing features of 1 and22+ via the involvement of the available N–H proton in the framework of coordinated HL2− have been evaluatedby different experimental investigations, in conjunction with the DFT calculations, using a wide variety ofanions such as F−, Cl−, Br−, I−, OAc−, SCN−, HSO4− and H2PO4−. This, however, establishes that both 1 and 22+are equally efficient in recognising the F− ion selectively, with log K values of 6.83 and 5.89, respectively.
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6.
  • Ahlsten, Nanna, et al. (författare)
  • Allylic alcohols as synthetic enolate equivalents : Isomerisation and tandem reactions catalysed by transition metal complexes
  • 2012
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41:6, s. 1660-1670
  • Tidskriftsartikel (refereegranskat)abstract
    • Allylic alcohols can be isomerised into carbonyl compounds by transition metal complexes. In the last few years, catalyst design and development have resulted in highly efficient isomerisations under mild reaction conditions, including enantioselective versions. In addition, the isomerisation of allylic alcohols has been combined with C-C bond forming reactions when electrophiles such as aldehydes or imines were present in the reaction mixture. Also, C-F bonds can be formed when electrophilic fluorinating reagents are used. Thus, allylic alcohols can be treated as latent enol(ate)s. In this article, we highlight the latest developments concerning the isomerisation of allylic alcohols into carbonyl compounds, focusing in particular on tandem isomerisation/C-C or C-heteroatom bond formation processes. Significant attention is given to the mechanistic aspects of the reactions.
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7.
  • Andersson, Claes-Henrik, 1980-, et al. (författare)
  • Synthesis and characterization of a ferrocene-linked bis-fullerene[60] dumbbell
  • 2012
  • Ingår i: Dalton Transactions. - 1477-9226 .- 1477-9234. ; 41:8, s. 2374-2381
  • Tidskriftsartikel (refereegranskat)abstract
    • A new [60]fullerene dumbbell consisting of two fulleropyrrolidines connected to a central ferrocene unit by amide linkages has been prepared and fully characterized by elemental analysis, 1H NMR, UV/Vis, fluorescence and mass spectrometry. The electrochemical properties as determined by cyclic voltammetry show ground state electronic communication between the ferrocene and the fullerene units. In addition, the preparaton of a ferrocene building block for an alternative linking approach is presented.
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8.
  • Aureliano, Manuel, et al. (författare)
  • Ion pumps as biological targets for decavanadate
  • 2013
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 42:33, s. 11770-11777
  • Tidskriftsartikel (refereegranskat)abstract
    • The putative applications of poly-, oligo-and mono-oxometalates in biochemistry, biology, pharmacology and medicine are rapidly attracting interest. In particular, these compounds may act as potent ion pump inhibitors and have the potential to play a role in the treatment of e. g. ulcers, cancer and ischemic heart disease. However, the mechanism of action is not completely understood in most cases, and even remains largely unknown in other cases. In the present review we discuss the most recent insights into the interaction between mono-and polyoxometalate ions with ion pumps, with particular focus on the interaction of decavanadate with Ca2+-ATPase. We also compare the proposed mode of action with those of established ion pump inhibitors which are currently in therapeutic use. Of the 18 classes of compounds which are known to act as ion pump inhibitors, the complete mechanism of inhibition is only known for a handful. It has, however, been established that most ion pump inhibitors bind mainly to the E2 ion pump conformation within the membrane domain from the extracellular side and block the cation release. Polyoxometalates such as decavanadate, in contrast, interact with Ca2+-ATPase near the nucleotide binding site domain or at a pocket involving several cytoplasmic domains, and therefore need to cross through the membrane bilayer. In contrast to monomeric vanadate, which only binds to the E2 conformation, decavanadate binds to all protein conformations, i.e. E1, E1P, E2 and E2P. Moreover, the specific interaction of decavanadate with sarcoplasmic reticulum Ca2+-ATPase has been shown to be non-competitive with respect to ATP and induces protein cysteine oxidation with concomitant vanadium reduction which might explain the high inhibitory capacity of V-10 (IC50 = 15 mu M) which is quite similar to the majority of the established therapeutic drugs.
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9.
  • Bajnóczi, Eva, et al. (författare)
  • Speciation and structure of tin(II) in hyper-alkaline aqueous solution
  • 2014
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43, s. 17971–17979-
  • Tidskriftsartikel (refereegranskat)abstract
    • The identity of the predominating tin(II)-hydroxide complex formed in hyper-alkaline aqueous solutions (0.2 <= C-NaOH <= 12 mol dm(-3)) is determined by potentiometric titrations, Raman, Mossbauer and XANES spectroscopy, supplemented by quantum chemical calculations. Thermodynamic studies using a H-2/Pt electrode up to free hydroxide concentrations of 1 mol dm(-3) showed the presence of a single monomeric complex with a tin(II) : hydroxide ratio of 1 : 3. This observation together with Raman and Mossbauer spectroscopic measurements supplemented by quantum mechanical calculations proved that the predominating complex is [Sn(OH)(3)](-), and that the presence of the other possible complex, [SnO(OH)](-), could not be proven with either experiments or simulations. The structure of the trihydroxidostannate(II) complex, [Sn(OH)(3)](-), was determined by EXAFS and was found to be independent of the applied hydroxide and tin(II) concentrations. The mean Sn-O bond distance is short, 2.078 angstrom, and in very good agreement with the only structure reported in the solid state. It is also shown that at pH values above 13 the speciation of the predominant trihydroxidostannate(II) complex is not affected by the presence of high concentrations of chloride ions.
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10.
  • Bajnóczi, Eva, et al. (författare)
  • Speciation and the structure of lead(II) in hyperalkaline aqueous solution
  • 2014
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43, s. 17539-17543
  • Tidskriftsartikel (refereegranskat)abstract
    • The identity of the predominating lead(II) species in hyper-alkaline aqueous solution has been determined by Raman spectroscopy, and ab initio quantum chemical calculations and its structure has been determined by EXAFS. The observed and calculated Raman spectra for the [Pb(OH)(3)](-) complex are in agreement while they are different for two-coordinated complexes and complexes containing Pb=O double bonds. Predicted bond lengths are also consistent with the presence of [Pb(OH)(3)](-) and exclude the formation of Pb=O double bond(s). These observations together with experimentally established analogies between lead(II) and tin(II) in hyper-alkaline aqueous solutions suggest that the last stepwise hydroxido complex of lead(II) is [Pb(OH)(3)](-). The Pb-O bond distance in the [Pb(OH)(3)](-) complex as determined is remarkably short, 2.216 angstrom, and has low symmetry as no multiple back-scattering is observed. The [Pb(OH)(3)](-) complex has most likely trigonal pyramidal geometry as all reported three-coordinated lead(II) complexes in the solid state. From single crystal X-ray data, the bond lengths for O-coordinated lead(II) complexes with low coordination numbers are spread over an unusually wide interval, 2.216-2.464 angstrom for N = 3. The Pb-O bond distance is at the short side and within the range of three coordinated complexes, as also observed for the trihydroxidostannate(II) complex indicating that the hydroxide ion forms short bonds with d(10)s(2) metal ions with occupied anti-bonding orbitals.
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11.
  • Berggren, Gustav, et al. (författare)
  • Synthesis and characterisation of low valent Mn-complexes as models for Mn-catalases
  • 2010
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 39:45, s. 11035-11044
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work we report the synthesis of two novel manganese complexes, [L1(3)Mn(6)(II)](ClO4)(6) (1 center dot(ClO4)(6)) and [L2Mn(2)(II)(mu-OAc)(mu-Cl)](ClO4)(2) (2 center dot(ClO4)(2)), where L1(2-) is the 2,2'-(1,3-phenylenebis(methylene))bis-((2-(bis(pyridin-2-ylmethyl)amino)ethyl)azanediyl)diacetic acid anion and L2 is N1,N1'-(1,3-phenylenebis(methylene))bis(N2,N2'-bis(pyridin-2-ylmethyl)ethane-1,2-diamine). The ligands Na(2)L1 and L2 are built on the same backbone, L2 only contains nitrogen donors, while two carboxylate arms have been introduced in Na(2)L1. The two complexes have been characterized by single-crystal X-ray diffraction, magnetic susceptibility, EPR spectroscopy, and electrochemistry. X-Ray crystallography revealed that 1 is a manganese(II) hexamer and 2 is a manganese(II) dimer featuring an unprecedented mono-mu-acetato, mono-mu-chlorido bridging motif. The ability of the complexes to catalyse H2O2 disproportionation, thereby acting as models for manganese catalases, has been investigated and compared to the activity of two other related manganese complexes. The introduction of carboxylate donors in the ligands, leading to increased denticity, resulted in a drop in H2O2 disproportionation activity.
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12.
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13.
  • Brink, A., et al. (författare)
  • Fast and reversible insertion of carbon dioxide into zirconocene-alkoxide bonds. A mechanistic study
  • 2014
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43:23, s. 8894-8898
  • Tidskriftsartikel (refereegranskat)abstract
    • In two consecutive equilibria the compound (Cp*)(2)Zr(OMe)(2) undergoes insertion of CO2 to form the mono- and bis-hemicarbonates. Both equilibria are exothermic but entropically disfavoured. Magnetisation transfer experiments gave kinetic data for the first equilibrium showing that the rate of insertion is overall second order with a rate constant of 3.20 +/- 0.12 M-1 s(-1), which is substantially higher than those reported for other early transition metal alkoxides, which are currently the best homogeneous catalysts for dimethyl carbonate formation from methanol and CO2. Activation parameters for the insertion reaction point to a highly ordered transition state and we interpret that as there being a substantial interaction between the CO2 and the metal during the C-O bond formation. This is supported by DFT calculations showing the lateral attack by CO2 to have the lowest energy transition state.
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14.
  • Buehl, Michael, et al. (författare)
  • Binding modes of oxalate in UO(2)(oxalate) in aqueous solution studied with first-principles molecular dynamics simulations. Implications for the chelate effect
  • 2011
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 40:42, s. 11192-11199
  • Tidskriftsartikel (refereegranskat)abstract
    • Car-Parrinello molecular dynamics simulations are reported for aqueous UO(2)(H(2)O)(n)(C(2)O(4)) (n = 3, 4), calling special attention to the binding modes of oxalate and the thermodynamics of the so-called chelate effect. Based on free energies from thermodynamic integration (BLYP functional), the kappa(1),kappa(1')-binding mode of the oxalate (with one O atom from each carboxylate coordinating) is more stable than kappa(2) (2 O atoms from the same carboxylate) and kappa(1) forms by 23 and 39 kJ mol(-1), respectively. The free energy of binding a fourth water ligand to UO(2)(H(2)O)(3)(kappa(1)-C(2)O(4)) is computed to be low, 12 kJ mol(-1). Changes of the hydration shell about oxalate during chelate opening are discussed. Composite enthalpies and free energies, obtained from both experiment and quantum-chemical modeling, are proposed for the formation of monodentate UO(2)(H(2)O)(4)(kappa(1)-C(2)O(4)). These data suggest that the largest entropy change in the overall complex formation occurs at this stage, and that the subsequent chelate closure under water release is essentially enthalpy-driven.
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15.
  • Bäcktorp, Carina, 1964, et al. (författare)
  • A DFT comparison of the neutral and cationic Heck pathways.
  • 2011
  • Ingår i: Dalton transactions (Cambridge, England : 2003). - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 40, s. 11308-11314
  • Tidskriftsartikel (refereegranskat)abstract
    • The two distinct mechanistic pathways of the Heck reaction, cationic and neutral, are characterized computationally using DFT calculations with corrections for solvation and dispersion. The selectivity in each type of reaction is discussed in terms of the detailed reaction paths, and the two types are compared to each other. The geometries and energies of the selectivity-determining transitions states are analyzed in detail.
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16.
  • Cadu, Alban, 1987-, et al. (författare)
  • Iridium catalysis : Application of asymmetric reductive hydrogenation
  • 2013
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 42:40, s. 14345-14356
  • Tidskriftsartikel (refereegranskat)abstract
    • Iridium, despite being one of the least abundant transition metals, has found several uses. N,P-ligated iridium catalysts are used to perform many highly selective reactions. These methodologies have been developed extensively over the past 15 years. More recently, the application of iridium N,P catalysts in asymmetric hydrogenation has been a focus of research to find novel applications and to expand on their current synthetic utility. The aim of this perspective is to highlight the advances made by the Andersson group.
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17.
  • Castillo, Ivan, et al. (författare)
  • Structural, spectroscopic, and electrochemical properties of tri- and tetradentate N-3 and N3S copper complexes with mixed benzimidazole/thioether donors
  • 2012
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 41:31, s. 9394-9404
  • Tidskriftsartikel (refereegranskat)abstract
    • Cupric and cuprous complexes of bis(2-methylbenzimidazolyl)(2-methylthiophene) amine (L-1), bis(2-methylbenzimidazolyl)benzylamine (L-2), bis(2-methylbenzimidazolyl)(2,4-dimethylphenylthioethyl)-amine (L-3), bis(1-methyl-2-methylbenzimidazolyl)benzylamine (Me2L2), and bis(1-methyl-2-methylbenzimidazolyl)(2,4-dimethylphenylthioethyl)amine (Me2L3) have been spectroscopically, structurally, and electrochemically characterised. The thioether-containing ligands L-3 and Me2L3 give rise to complexes with Cu-S bonds in solution and in the solid state, as evidenced by UV-vis spectroscopy and X-ray crystallography. The Cu2+ complexes [(LCuCl2)-Cu-1] (1), [(LCuCl2)-Cu-2] (2) and [(Me2LCuCl)-Cu-3]ClO4 (3(Me,ClO4)) are monomeric in solution according to ESI mass spectrometry data, as well as in the solid state. Their Cu+ analogues [(LCu)-Cu-1]ClO4, [(LCu)-Cu-2]ClO4, [(LCu)-Cu-3]ClO4 (4-6), [(BOC2LCu)-Cu-1(NCCH3)]ClO4 (4(BOC)), [(Me2LCu)-Cu-2(NCCH3)(2)]PF6 (5(Me)) and [(Me2LCu)-Cu-3](2)(ClO4)(2) (6(Me)) are also monomeric in acetonitrile solution, as confirmed crystallographically for 4(BOC) and 5(Me). In contrast, 6(Me) is dimeric in the solid state, with the thioether group of one of the ligands bound to a symmetry-related Cu+ ion. Cyclic voltammetry studies revealed that the bis(2-methylbenzimidazolyl) amine-Cu2+/Cu+ systems possess half-wave potentials in the range -0.16 to -0.08 V (referenced to the ferrocenium-ferrocene couple); these values are nearly 0.23 V less negative than those reported for related bis(picolyl) amine-derived ligands. Based on these observations, the N-3 or N3S donor set of the benzimidazole-derived ligands is analogous to previously reported chelating systems, but the electronic environment they provide is unique, and may have relevance to histidine and methionine-containing metalloenzymes. This is also reflected in the reactivity of [(Me2LCu)-Cu-2(NCCH3)(2)](+) (5(Me)) and [(Me2LCu)-Cu-3](+) (6(Me)) towards dioxygen, which results in the production of the superoxide anion in both cases. The thioether-bound Cu+ centre in 6(Me) appears to be more selective in the generation of O-2(center dot-) than 5(Me), lending evidence to the hypothesis of the modulating properties of thioether ligands in Cu-O-2 reactions.
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18.
  • Chen, Hong, et al. (författare)
  • Layered V-B-O Polyoxometalate Nets Linked by Diethylenetriamine Complexes with Dangling Amine Groups
  • 2014
  • Ingår i: Dalton Transactions. - 1477-9226 .- 1477-9234. ; 43:41, s. 15283-15286
  • Tidskriftsartikel (refereegranskat)abstract
    • Two layered V-B-O contained polyoxometalate (POM) net structures, denoted as SUT-12 and SUT-13, are reported here. SUT-12 was synthesized by the boric acid flux method, and it represents the first 2D structure constructed from the V6B20 vanadoborate cluster. SUT-13 was synthesized through the hydrothermal method and constructed from V12B6P12 vanadium borophosphate clusters. In both structures, the vanadoborate or vanadium borophosphate clusters were linked through in-situ formed Zn(DETA)2 or Cu(DETA)2 complexes. Surprisingly, for all DETA molecules in the two metal complexes, there is one dangling amine group when it coordinated to the metal. The phenomena of the dangling amine group feature is abnormal and the Cu(DETA)2 complexes in SUT-13 was taken as an example and studied by density function theory (DFT) calculation in order to understand this unusual feature.
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19.
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20.
  • Davies, K., et al. (författare)
  • Anionic zinc-trimesic acid MOFs with unusual topologies: Reversible hydration studies
  • 2010
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 39:11, s. 2869-2874
  • Tidskriftsartikel (refereegranskat)abstract
    • The reaction of 1,3,5-benzenetricarboxylic acid (H3BTC) with ZnSO4 center dot 6H(2)O in a DMF-water solution afforded two new metal-organic frameworks [Zn-6(mu(3)-OH)(2)(BTC)(4)(DMF)(2.5)(H2O)(2)]center dot[Zn(H2O)(3)(DMF)(3)]center dot 3.1H(2)O (1) and Zn-2(HBTC)(BTC)(H2O)(3)]center dot DMA center dot 3H(2)O (2). Both compounds are thermally stable and can be prepared reproducibly. Rehydration experiments on compound 2 demonstrate reversible dehydration and rehydration while 1 rehydrates to a different crystalline material. Network analysis revealed a binodal (3,6)-net for 1 and a (3,5)-net for 2, both rare topologies.
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21.
  • Diesen, Veronica, et al. (författare)
  • Silver enhanced TiO2 thin films : photocatalytic characterization using aqueous solutions of tris(hydroxymethyl)aminomethane
  • 2014
  • Ingår i: Dalton Transactions. - 1477-9226 .- 1477-9234. ; 43:1, s. 344-351
  • Tidskriftsartikel (refereegranskat)abstract
    • The photocatalytic activity in aqueous solutions of TiO2 and Ag enhanced TiO2 sol-gel produced films was characterized using tris(hydroxymethyl)aminomethane (Tris) under black light (365 nm) and the observed differences in efficiency were further investigated by O-2 adsorption studies using the same probe. Hydrogen abstracting species, such as hydroxyl radicals formed upon photocatalysis, are able to abstract hydrogen from Tris. This reaction leads to the formation of formaldehyde which was detected and quantified through a modified version of the Hantzsch reaction. It was found that the Ag enhanced TiO2 film increased the apparent quantum yield from 7% to 12%, partly as a result of a Schottky barrier formation at the metal-semiconductor interface and partly as the sensitizing effect of Ag nanoparticles extends the visible light absorption, which through electron transfer processes enable an efficient charge separation in the TiO2 by attracting acceptor species more efficiently than pure TiO2. The O-2 adsorption studies in this paper showed that the Ag enhanced TiO2 film has a stronger adsorption affinity than pure TiO2 towards O-2, which make the reduction of O-2 more efficient with a subsequent enhanced electron-hole lifetime. It was also found that the Ag enhanced TiO2 film had a poorer adsorption affinity for Tris than the pure TiO2 film, which is a consequence of fewer available surface adsorption sites due to the Ag coverage at 64% which agrees well with the obtained adsorption equilibrium constants (K-LH(TiO2) = 615 M-1 and KLH(Ag-TiO2) = 320 M-1).
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22.
  • Driver, Gordon W, et al. (författare)
  • The complex story of a simple Brønsted acid : Unusual speciation of HBr in an ionic liquid medium
  • 2011
  • Ingår i: Dalton Transactions. - : RSC Publishing. - 1477-9226 .- 1477-9234. ; 40:41, s. 10801-10803
  • Tidskriftsartikel (refereegranskat)abstract
    • Crystalline solids, co-existing in equilibrium with the 3-methyl-1H-imidazolium bromohydrogenates(i) ionic liquid, have been characterised by X-ray diffraction analysis. The Brønsted acidic, homo-conjugate [H(2)Br(3)](-) anions presented are discussed in terms of their structure and reactivity, in efforts to advance the understanding of Brønsted acidity in ionic liquid media.
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23.
  • Ekberg, Christian, 1967, et al. (författare)
  • The structure of plutonium(IV) oxide as hydrolysed clusters in aqueous suspensions
  • 2013
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 42:6, s. 2035-2040
  • Tidskriftsartikel (refereegranskat)abstract
    • The behavior of plutonium still puzzles scientists 70 years after its discovery. There are several factors making the chemistry of plutonium interesting including its ability to keep several oxidation states. Another unique property is that the oxidation states +III, +IV, +V and +VI may exist simultaneously in solution. Another property plutonium shares with some other tetravalent metal ions is the ability to form stable polynuclear complexes or colloids. The structures of freshly prepared and five-year old plutonium(IV) colloids are compared with crystalline plutonium(IV) oxide using Pu L-3-edge EXAFS. It was shown that as the plutonium colloids age they do in fact shrink in size, contrary to previous expectations. The aged colloidal particles are indeed very small with only 3-4 plutonium atoms, and with a structure very similar to solid plutonium(IV) oxide, but with somewhat shorter mean Pu-O bond and Pu. Pu distances indicating a partial oxidation. The very small size of the colloidal particles is further supported by the fact that they do not sediment on heavy ultra-centrifugation.
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24.
  • Eklund, Lars, et al. (författare)
  • On the structure and dynamics of the hydrated sulfite ion in aqueous solution - an ab initio QMCF MD simulation and large angle X-ray scattering study
  • 2012
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41, s. 5209-5216
  • Tidskriftsartikel (refereegranskat)abstract
    • Theoretical ab initio quantum mechanical charge field molecular dynamics (QMCF MD) formalism has been applied in conjunction to experimental large angle X-ray scattering to study the structure and dynamics of the hydrated sulfite ion in aqueous solution. The results show that there is a considerable effect of the lone electron-pair on sulfur concerning structure and dynamics in comparison with the sulfate ion with higher oxidation number and symmetry of the hydration shell. The S-O bond distance in the hydrated sulfite ion has been determined to 1.53(1) angstrom by both methods. The hydrogen bonds between the three water molecules bound to each sulfite oxygen are only slightly stronger than those in bulk water. The sulfite ion can therefore be regarded as a weak structure maker. The water exchange rate is somewhat slower for the sulfite ion than for the sulfate ion, tau(0.5) = 3.2 and 2.6 ps, respectively. An even more striking observation in the angular radial distribution (ARD) functions is that the for sulfite ion the water exchange takes place in close vicinity of the lone electron-pair directed at its sides, while in principle no water exchange did take place of the water molecules hydrogen bound to sulfite oxygens during the simulation time. This is also confirmed when detailed pathway analysis is conducted. The simulation showed that the water molecules hydrogen bound to the sulfite oxygens can move inside the hydration shell to the area outside the lone electron-pair and there be exchanged. On the other hand, for the hydrated sulfate ion in aqueous solution one can clearly see from the ARD that the distribution of exchange events is symmetrical around the entire hydration sphere.
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25.
  • Eklund, Lars, et al. (författare)
  • Structure and hydrogen bonding of the hydrated selenite and selenate ions in aqueous solution
  • 2014
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43, s. 6315-6321
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure and hydrogen bonding of the hydrated selenite, SeO32-, and selenate, SeO42-, ions have been studied in aqueous solution by large angle X-ray scattering (LAXS), EXAFS and double difference infrared (DDIR) spectroscopy. The mean Se-O bond distances are 1.709(2) and 1.657(2) angstrom, respectively, as determined by LAXS, and 1.701(3) and 1.643(3) angstrom by EXAFS. These bond distances are slightly longer than the mean distances found in the solid state, 1.691 and 1.634 angstrom, respectively. The structures of HSeO3-, H2SeO3 and HSeO4- in aqueous solution have been determined by EXAFS giving the same Se-O bond distances as for the selenite and selenate ions, respectively. The mean Se center dot center dot center dot O-w distance to the water molecules hydrogen binding to selenite oxygens is 3.87(2) angstrom, and it is 4.36(8) angstrom to those clustered outside the lone electron-pair. The selenate ion has a symmetric hydration shell with only one Se center dot center dot center dot O-w distance, 3.94(2) angstrom. The mean Se-O center dot center dot center dot O-w angle in the hydrated selenite ion is 114.5, and the large temperature factor of the Se. Ow distance strongly indicates equilibrium between two and three water molecules hydrogen bound to the selenite oxygens. The mean Se- O. Ow angle in the hydrated selenate ion is 120 which strongly indicates that two water molecules hydrogen bind to the selenate oxygens. The DDIR spectra show peaks for the affected water bound to the selenite and selenate ions at 2491 +/- 2 and 2480 +/- 39 cm(-1), respectively, compared to 2509 cm(-1) in pure water. This shows that the selenite and selenate ions shall be regarded as weak structure makers.
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26.
  • Eklund, Lars, et al. (författare)
  • Structure and water exchange of the hydrated thiosulfate ion in aqueous solution using QMCF MD simulation and large angle X-ray scattering
  • 2014
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43, s. 12711-12720
  • Tidskriftsartikel (refereegranskat)abstract
    • Theoretical ab initio quantum mechanical charge field molecular dynamics (QMCF MD) has been applied in conjunction with experimental large angle X-ray scattering (LAXS) to study the structure and dynamics of the hydrated thiosulfate ion, S2O32-, in aqueous solution. The S-O and S-C-S-T bond distances have been determined to be 1.479(5) and 2.020(6) angstrom by LAXS and to be 1.478 and 2.017 angstrom by QMCF MD simulations, which are slightly longer than the mean values found in the solid state, 1.467 and 2.002 angstrom, respectively. This is due to the hydrogen bonds formed at hydration. The water dynamics show that water molecules are exchanged at the hydrated oxygen and sulfur atoms, and that the water exchange is ca. 50% faster at the sulfur atom than at the oxygen atoms with mean residence times, tau(0.5), of 2.4 and 3.6 ps, respectively. From this point of view the water exchange dynamics mechanism resembles the sulfate ion, while it is significantly different from the sulfite ion. This shows that the lone electron-pair in the sulfite ion has a much larger impact on the water exchange dynamics than a substitution of an oxygen atom for a sulfur one. The LAXS data did give mean S-C...O-aq1 and S-C...O-aq2 distances of 3.66(2) and 4.36(10) angstrom, respectively, and S-C-O-thio and O-thio...O-aq1, S-C-S-T and S-T...O-aq2 distances of 1.479(5), 2.845(10), 2.020(6) and 3.24(5) angstrom, respectively, giving S-C-O-thio...O-aq1 and S-C-S-T...O-aq2 angles close to 110 degrees, strongly indicating a tetrahedral geometry around the terminal thiosulfate sulfur and the oxygens, and thereby, three water molecules are hydrogen bound to each of them. The hydrogen bonds between thiosulfate oxygens and the hydrating water molecules are stronger and with longer mean residence times than those between water molecules in the aqueous bulk, while the opposite is true for the hydrogen bonds between the terminal thiosulfate sulfur and the hydrating water molecules. The hydration of all oxo sulfur ions is discussed using the detailed observations for the sulfate, thiosulfate and sulfite ions, and the structure of the hydrated peroxodisulfate ion, S2O82-, in aqueous solution has been determined by means of LAXS to support the general observations. The mean S-O bond distances are 1.448(2) and 1.675(5) angstrom to the oxo and peroxo oxygens, respectively.
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27.
  • Eurenius, Karinh, 1980, et al. (författare)
  • Role of B-site ion on proton conduction in acceptor-doped Sm(2)B(2)O(7-δ) (B = Ti, Sn, Zr and Ce) pyrochlores and C-type compounds.
  • 2011
  • Ingår i: Dalton transactions (Cambridge, England : 2003). - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 40:15, s. 3946-54
  • Tidskriftsartikel (refereegranskat)abstract
    • Proton conduction in three pyrochlores, Sm(1.92)Ca(0.08)B(2)O(7-δ), B = Ti, Sn, Zr and one phase with a related C-type fluorite superstructure, B = Ce, has been investigated. The samples were prepared by solid state reaction. Infrared spectroscopy measurements and thermogravimetric analysis were carried out to study the extent of proton dissolution and determine its dependence on the B-site ion. Electrochemical impedance spectroscopy, performed on heating and cooling pre-hydrated samples, confirmed significant levels of proton conduction for Sm(1.92)Ca(0.08)Ti(2)O(7-δ) and Sm(1.92)Ca(0.08)Sn(2)O(7-δ) up to T∼ 500 °C. In comparison the B = Zr and Ce samples revealed lower levels of proton conductivity, confined to temperatures below ∼ 400 °C. Proton diffusion coefficients of 3.36 × 10(-8), 1.73 × 10(-9), 5.53 × 10(-10) and 2.78 × 10(-11) cm(2) s(-1) were determined at 300 °C for samples with B = Ti, Sn, Zr and Ce respectively. The proton mobility of Sm(1.92)Ca(0.08)Ti(2)O(7-δ) is therefore approximately one order of magnitude lower than that found in yttrium-doped perovskite phases such as BaZrO(3) and BaCeO(3).
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28.
  • Farnum, Byron H., et al. (författare)
  • Influence of ion pairing on the oxidation of iodide by MLCT excited states
  • 2011
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 40:15, s. 3830-3838
  • Tidskriftsartikel (refereegranskat)abstract
    • The oxidation of iodide to diiodide, I2[radical dot]-, by the metal-to-ligand charge-transfer (MLCT) excited state of [Ru(deeb)3]2+, where deeb is 4,4[prime or minute]-(CO2CH2CH3)2-2,2[prime or minute]-bipyridine, was quantified in acetonitrile and dichloromethane solution at room temperature. The redox and excited state properties of [Ru(deeb)3]2+ were similar in the two solvents; however, the mechanisms for excited state quenching by iodide were found to differ significantly. In acetonitrile, reaction of [Ru(deeb)3]2+* and iodide was dynamic (lifetime quenching) with kinetics that followed the Stern-Volmer model (KD = 1.0 +/- 0.01 [times] 105 M-1, kq = 4.8 [times] 1010 M-1 s-1). Excited state reactivity was observed to be the result of reductive quenching that yielded the reduced ruthenium compound, [Ru(deeb-)(deeb)2]+, and the iodine atom, I[radical dot]. In dichloromethane, excited state quenching was primarily static (photoluminescence amplitude quenching) and [Ru(deeb-)(deeb)2]+ formed within 10 ns, consistent with the formation of ion pairs in the ground state that react rapidly upon visible light absorption. In both solvents the appearance of I2[radical dot]- could be time resolved. In acetonitrile, the rate constant for I2[radical dot]- growth, 2.2 +/- 0.2 [times] 1010 M-1 s-1, was found to be about a factor of two slower than the formation of [Ru(deeb-)(deeb)2]+, indicating it was a secondary photoproduct. The delayed appearance of I2[radical dot]- was attributed to the reaction of iodine atoms with iodide. In dichloromethane, the growth of I2[radical dot]-, 1.3 +/- 0.4 [times] 1010 M-1 s-1, was similar to that in acetonitrile, yet resulted from iodine atoms formed within the laser pulse. These results are discussed within the context of solar energy conversion by dye-sensitized solar cells and storage via chemical bond formation.
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29.
  • Fraqueza, Gil, et al. (författare)
  • Decavanadate, decaniobate, tungstate and molybdate interactions with sarcoplasmic reticulum Ca2+-ATPase : quercetin prevents cysteine oxidation by vanadate but does not reverse ATPase inhibition
  • 2012
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41:41, s. 12749-12758
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently we demonstrated that the decavanadate (V-10) ion is a stronger Ca2+-ATPase inhibitor than other oxometalates, such as the isoelectronic and isostructural decaniobate ion, and the tungstate and molybdate monomer ions, and that it binds to this protein with a 1 : 1 stoichiometry. The V-10 interaction is not affected by any of the protein conformations that occur during the process of calcium translocation (i.e. E1, E1P, E2 and E2P) (Fraqueza et al., J. Inorg. Biochem., 2012). In the present study, we further explore this subject, and we can now show that the decaniobate ion, [Nb-10 = Nb10O28](6-), is a useful tool in deducing the interaction and the non-competitive Ca2+-ATPase inhibition by the decavanadate ion [V-10 = V10O28](6-). Moreover, decavanadate and vanadate induce protein cysteine oxidation whereas no effects were detected for the decaniobate, tungstate or molybdate ions. The presence of the antioxidant quercetin prevents cysteine oxidation, but not ATPase inhibition, by vanadate or decavanadate. Definitive V(IV) EPR spectra were observed for decavanadate in the presence of sarcoplasmic reticulum Ca2+-ATPase, indicating a vanadate reduction at some stage of the protein interaction. Raman spectroscopy clearly shows that the protein conformation changes that are induced by V-10, Nb-10 and vanadate are different from the ones induced by molybdate and tungstate monomer ions. Here, Mo and W cause changes similar to those by phosphate, yielding changes similar to the E1P protein conformation. The putative reduction of vanadium(V) to vanadium(IV) and the non-competitive binding of the V-10 and Nb-10 decametalates may explain the differences in the Raman spectra compared to those seen in the presence of molybdate or tungstate. Putting it all together, we suggest that the ability of V-10 to inhibit the Ca2+-ATPase may be at least in part due to the process of vanadate reduction and associated protein cysteine oxidation. These results contribute to the understanding and application of these families of mono-and polyoxometalates as effective modulators of many biological processes, particularly those associated with calcium homeostasis.
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30.
  • Freys, Jonathan C., et al. (författare)
  • Ru-based donor-acceptor photosensitizer that retards charge recombination in a p-type dye-sensitized solar cell
  • 2012
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41:42, s. 13105-13111
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the synthesis and characterization of a donor-acceptor ruthenium polypyridyl complex as a photosensitizer for p-type dye-sensitized solar cells (DSSCs). The electrochemical, photophysical, and photovoltaic performance of two ruthenium-based photosensitizers were tested in NiO-based DSSCs; bis-(2,2′-bipyridine-4,4′-dicarboxylic acid) 2N-(1,10-phenanthroline)-4-nitronaphthalene-1,8-dicarboximide ruthenium(ii), ([Ru(dcb) 2(NMI-phen)](PF 6) 2) and tris-(2,2′-bipyridine-4,4′-dicarboxylic acid) 3 ruthenium(ii), [(Ru(dcb) 3)Cl 2]. The presence of an electron-accepting group, 4-nitronaphthalene-1,8-dicarboximide (NMI), attached to the phenanthroline of [Ru(dcb) 2(NMI-phen)] 2+ resulted in long-lived charge separation between reduced [Ru(dcb) 2(NMI-phen)] 2+ and NiO valence band holes; 10-50 μs. In the reduced state for [Ru(dcb) 2(NMI-phen)] 2+, the electron localized on the distal NMI group. In tests with I 3 -/I - and Co(4,4′-di-tert-butyl-bipyridine) 3 2+/3+ electrolytes, [Ru(dcb) 2(NMI-phen)] 2+ outperformed [Ru(dcb) 3] 2+ in solar cell efficiency in devices. A record APCE (25%) was achieved for a ruthenium photosensitizer in a p-type DSSC. Insights on photosensitizer regeneration kinetics are included.
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31.
  • Friedman, Ran (författare)
  • Structural and computational insights into the versatility of cadmium binding to proteins
  • 2014
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43:7, s. 2878-2887
  • Tidskriftsartikel (refereegranskat)abstract
    • Cadmium is a highly toxic group XII metal, similar to zinc and mercury. Unlike zinc, which is one of the most common metal cofactors in biology, cadmium is highly toxic. Many Zn2+-binding proteins can bind Cd2+-ions without significantly affecting their structures. Here, the protein data bank is analysed with regard to protein-cadmium interactions, which shows that cadmium can bind to a variety of ion binding sites in proteins. Statistical analysis of Cd2+-side chain interactions is compared with a similar analysis of other ions. This analysis reveals that with regard to amino acid side-chain preference, Cd2+ is more similar to Mn2+ than to Zn2+ or Hg2+. Finally, the interaction energies of three native metal binding proteins are calculated where Cd2+ binds instead of Zn2+, Ca2+ or Cu2+. The interaction energies are decomposed into individual components whose contributions are discussed.
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32.
  • García-Gallego, Sandra, et al. (författare)
  • Anionic sulfonated and carboxylated PPI dendrimers with the EDA core : synthesis and characterization of selective metal complexing agents.
  • 2013
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 42:16, s. 5874-89
  • Tidskriftsartikel (refereegranskat)abstract
    • Herein we describe the synthesis and characterization of new sulfonated and carboxylated poly(propyleneimino) (PPI) dendrimers with the ethylenediamino (EDA) core, at generations 1, 2 and 3. By means of UV-Vis and EPR spectroscopy, using Cu(2+) as a probe, we concluded that these dendrimers show a specific pattern in the coordination of metal ions. In agreement with the UV-Vis studies, EPR spectra of carboxylated compounds are constituted by 3 different signals which appear and then disappear with increasing copper concentration, corresponding to the saturation of different copper complexation sites. At the lowest copper concentration up to a 1:1 molar ratio between Cu(II) and the dendrimer, the spectrum is characteristic of a CuN2O2 coordination at the core of the dendrimer. The spectrum appearing at higher Cu(II) concentrations indicates a peripheral location of the ions coordinating one nitrogen and 3 oxygen atoms in a square planar geometry in restricted mobility conditions. For the highest concentrations tested, copper ions are confined at the external dendrimer surface with CuO4 coordination. For sulfonate systems, the EPR results are in line with a weaker interaction of Cu(II) with the nitrogen sites and a stronger interaction with the oxygen (SO3(-)) groups with respect to the interactions measured by EPR for carboxylate systems.
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33.
  • García-Gallego, Sandra, et al. (författare)
  • Polyanionic N-donor ligands as chelating agents in transition metal complexes : synthesis, structural characterization and antiviral properties against HIV
  • 2012
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 41:21, s. 6488-99
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe here the synthesis and characterization of new sulfonated and carboxylated-containing N-donor ligands [Na(4)(edts)]·4H(2)O (2), [Na(2)(dmeddp)]·2H(2)O (3) and [Na(4)(edtp)]·H(2)O (4) (edts = ethylene-diamine- N,N,N',N'-tetraethylenesulfonate ion; dmeddp = dimethyl-ethylene-diamine-N,N,N',N'-tetra-3-propionate ion; edtp = ethylene-diamine-N,N,N',N'-tetra-3-propionate ion) and their corresponding metal (Ni, Co, Cu and Zn) complexes. Mainly, UV-Vis and a computer aided analysis of the EPR spectra provided information on the geometry and structure of the complexes in solution. Some of the metal complexes inhibit HIV replication when treating both pre- and post-infected PBMC cells, and hustle the inhibitory effect compared to the metal salts alone.
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34.
  • Glans, Lotta, et al. (författare)
  • Ruthenium(ii) arene complexes with chelating chloroquine analogue ligands: Synthesis, characterization and in vitro antimalarial activity.
  • 2012
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 41:9, s. 2764-2773
  • Tidskriftsartikel (refereegranskat)abstract
    • Three new ruthenium complexes with bidentate chloroquine analogue ligands, [Ru(η(6)-cym)(L(1))Cl]Cl (1, cym = p-cymene, L(1) = N-(2-((pyridin-2-yl)methylamino)ethyl)-7-chloroquinolin-4-amine), [Ru(η(6)-cym)(L(2))Cl]Cl (2, L(2) = N-(2-((1-methyl-1H-imidazol-2-yl)methylamino)ethyl)-7-chloroquinolin-4-amine) and [Ru(η(6)-cym)(L(3))Cl] (3, L(3) = N-(2-((2-hydroxyphenyl)methylimino)ethyl)-7-chloroquinolin-4-amine) have been synthesized and characterized. In addition, the X-ray crystal structure of 2 is reported. The antimalarial activity of complexes 1-3 and ligands L(1), L(2) and L(3), as well as the compound N-(2-(bis((pyridin-2-yl)methyl)amino)ethyl)-7-chloroquinolin-4-amine (L(4)), against chloroquine sensitive and chloroquine resistant Plasmodium falciparum malaria strains was evaluated. While 1 and 2 are less active than the corresponding ligands, 3 exhibits high antimalarial activity. The chloroquine analogue L(2) also shows good activity against both the chloroquine sensitive and the chloroquine resistant strains. Heme aggregation inhibition activity (HAIA) at an aqueous buffer/n-octanol interface (HAIR(50)) and lipophilicity (D, as measured by water/n-octanol distribution coefficients) have been measured for all ligands and metal complexes. A direct correlation between the D and HAIR(50) properties cannot be made because of the relative structural diversity of the complexes, but it may be noted that these properties are enhanced upon complexation of the inactive ligand L(3) to ruthenium, to give a metal complex (3) with promising antimalarial activity.
  •  
35.
  • Glans, Lotta, et al. (författare)
  • Synthesis and biological activity of cymantrene and cyrhetrene 4-aminoquinoline conjugates against malaria, leishmaniasis, and trypanosomiasis.
  • 2012
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 41:21, s. 6443-6450
  • Tidskriftsartikel (refereegranskat)abstract
    • Organometallic analogues of chloroquine show promise as new antimalarial agents capable of overcoming resistance to the parent drug chloroquine. Here, the synthesis and characterization of three new cymantrene (CpMn(CO)(3)) and cyrhetrene (CpRe(CO)(3)) 4-aminoquinoline conjugates with either an amine or amide linker are reported. The antimalarial activity of the new organometallic conjugates N-(2-(7-chloroquinolin-4-ylamino)ethyl)-4-cymantrenylbutanamide (), N-(2-(7-chloroquinolin-4-ylamino)ethyl)-4-cyrhetrenylbutanamide () and N-(7-chloroquinolin-4-yl)-N'-(cymantrenylmethyl)ethane-1,2-diamine () was evaluated against a chloroquine-sensitive (CQS) and a chloroquine-resistant strain (CQR) of the malaria parasite Plasmodium falciparum. The cymantrene complex with an amine linker () showed good activity against the CQS strain but was inactive against the CQR strain. In contrast, cymantrene and cyrhetrene compounds with an amide linker were active against both the CQS and the CQR strain. In addition, the antibacterial, anti-trypanosomal and anti-leishmanial activity of the compounds was evaluated. Compound showed submicromolar activity against Trypanosoma brucei at a concentration where the toxicity to normal human cells is low. No significant effect was noticed on the exchange of manganese for rhenium in the CpM(CO)(3) moiety in any of the biological assays.
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36.
  • Guliashvili, Tamaz, et al. (författare)
  • Unsuccessful attempts to add alcohols to transient 2-amino-2-siloxy- silenes - leading to a new benign route for base-free alcohol protection
  • 2010
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 39:39, s. 9379-9385
  • Tidskriftsartikel (refereegranskat)abstract
    • Thermolytic formation of transient   1,1-bis(trimethylsilyl)-2-dimethylamino-2-trimethylsiloxysilene (2)  from N,N-dimethyl(tris(trimethylsilyl) silyl) methaneamide (1) in presence of a series of alcohols was investigated. The products are,  however, not the expected alcohol-silene addition adducts but   silylethers formed in nearly quantitative yields. Thermolysis of 1 in   the presence of both alcohols (MeOH or iPrOH) and 1,3-dienes   (1,3-butadiene or 2,3-dimethyl-1,3-butadiene) gives   alkyl-tris(trimethylsilyl)silylethers and the [4+2] cycloadducts   between the silene and diene, which confirms the presence of 2 and that   it is unreactive towards alcohols. The observed silylethers are substitution adducts where the amide group of the silylamide is replaced by an alkoxy group, and the reaction time is reflected in the   steric bulk of the alcohol. Indeed, the formation of silylethers from   the reaction of alcohols with silylamide represents a new base-free   method for protection of alcohols. The protection reactions using 1   progresses at elevated temperatures, or alternatively, under acid   catalysis at ambient temperature, and similar protections can be   carried out with N-cyclohexyl(triphenylsilyl) methaneamide and N,   N-dimethyl(trimethylsilyl) methaneamide. The latter silylamide can be used under neutral conditions at room temperature. The only by-products  are formamides (N,N-dimethylformamide (DMF) or N-cyclohexylformamide), and the reactions can be performed without solvent. In addition to alcohols we also examined the method for protection of diols, thiols   and carboxylic acids,and also these reactions proceeded in high yields and with good selectivities.
  •  
37.
  • Guo, Peng, et al. (författare)
  • Ab initio structure determination of interlayer expanded zeolites by single crystal rotation electron diffraction
  • 2014
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43:27, s. 10593-10601
  • Tidskriftsartikel (refereegranskat)abstract
    • Layered solids often form thin plate-like crystals that are too small to be studied by single-crystal X-ray diffraction. Although powder X-ray diffraction (PXRD) is the conventional method for studying such solids, it has limitations because of peak broadening and peak overlapping. We have recently developed a software-based rotation electron diffraction (RED) method for automated collection and processing of 3D electron diffraction data. Here we demonstrate the ab initio structure determination of two interlayer expanded zeolites, the microporous silicates COE-3 and COE-4 (COE-n stands for International Network of Centers of Excellence-n), from submicron-sized crystals by the RED method. COE-3 and COE-4 are built of ferrierite-type layers pillared by (-O-Si(CH3)(2)-O-) and (-O-Si(OH)(2)-O-) linker groups, respectively. The structures contain 2D intersecting 10-ring channels running parallel to the ferrierite layers. Because both COE-3 and COE-4 are electron-beam sensitive, a combination of RED datasets from 2 to 3 different crystals was needed for the structure solution and subsequent structure refinement. The structures were further refined by Rietveld refinement against the PXRD data. The structure models obtained from RED and PXRD were compared.
  •  
38.
  • Haeussermann, Ulrich, et al. (författare)
  • Electron-poor antimonides: complex framework structures with narrow band gaps and low thermal conductivity
  • 2010
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 39:4, s. 1036-1045
  • Tidskriftsartikel (refereegranskat)abstract
    • Binary zinc and cadmium antimonides and their ternary relatives with indium display complex crystal structures, but reveal at the same time narrow band gaps in their electronic structure at or close to the Fermi level. It is argued that these systems represent "electron-poor framework semiconductors" (EPFS) with average valence electron concentrations between three and four. EPFS materials constituted of metal and semimetal atoms form a common, weakly polar framework containing multi-center bonded structural entities. The localized multi-center bonding feature is thought to be the key to structurally complex semiconductors. In this respect electron-poor antimonides become related to modifications of elemental boron. Electron-poor antimonides show promising thermoelectric properties, especially through a remarkably low thermal conductivity. At the same time the thermal stability of these compounds is rather limited because of temperature polymorphism and/or comparatively low melting or decomposition temperatures ( usually below 600 K).
  •  
39.
  • Hanczyc, Piotr, 1985, et al. (författare)
  • Two-photon absorption of metal–organic DNA-probes
  • 2012
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41:11, s. 3123-3125
  • Tidskriftsartikel (refereegranskat)abstract
    • We report remarkable multiphoton absorption properties of DNA intercalating ruthenium complexes: (1) [Ru(phen)2dppz]2+; (2) [(11,11′-bidppz)(phen)4Ru2]4+; (3) [11,11′-bipb(phen)4Ru2]4+. Two-photon spectra in the range from 460 to 1100 nm were measured using the Z-scan technique. In particular, complex 2 was found to exhibit very strong two- and three-photon absorption properties, which could be an effect of symmetric charge transfer from the ends towards the middle of the conjugated dimeric orbital system. We propose that these molecules could provide a new generation of DNA binding nonlinear chromophores for wide applications in biology and material science. The combination of a large two-photon cross section and strong luminescence quantum yields for the molecules when intercalated makes the compounds uniquely bright and photo-stable probes for two-photon luminescence imaging and also promising as enhanced photosensitizers in two-photon sensitizing applications.
  •  
40.
  • Hennion, Clare, et al. (författare)
  • Kinetic and mechanistic investigation of the substitution reactions of four and five co-ordinated rhodium stibine complexes with a bulky phosphite
  • 2013
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 42:39, s. 14134-14139
  • Tidskriftsartikel (refereegranskat)abstract
    • The substitution reaction of trans-[Rh(Cl)(CO)(SbPh3)(2)] (1) with tris(2,4-di-tert-butylphenyl)phosphite (2,4-TBPP) to form trans-[Rh(Cl)(CO)(2,4-TBPP)(2)] (4) in two consecutive steps has been investigated by UV-vis stopped-flow spectrophotometry. The experiments were performed in dichloromethane and in ethyl acetate, at 298 K and 268 K respectively for the first reaction step, and for the second reaction step over a temperature range from 278 to 313 K in both solvents. The first step is very fast (up to 1630 s(-1)) and on the limit of what is observable with the stopped-flow technique. Introduction of the five-coordinate complex trans-[Rh(Cl)(CO)(SbPh3)(3)] (2) in equilibrium with (1), by adding an excess SbPh3, led to a significant decrease in overall reaction rate for the formation of the intermediate trans-[Rh(Cl)-(CO)(SbPh3)(2)(2,4-TBPP)] (3). Activation parameters for the second substitution reaction, in which 3 is converted to 4, has been determined as Delta H double dagger = 22.85 +/- 0.17 and 28.38 +/- 0.10 kJ mol(-1) and Delta S double dagger = - 144.7 +/- 0.6 and -100.9 +/- 0.4 J mol(-1) K-1 for CH2Cl2 and EtOAc respectively, supporting an associative pathway. A strongly coordinating solvent promotes both reactions. In all reaction steps a strong tendency for stibines to promote 5-coordinated, fairly stable intermediates is manifested.
  •  
41.
  • Hogarth, Graeme, et al. (författare)
  • Cluster chemistry in the Noughties: new developments and their relationship to nanoparticles
  • 2010
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 39:27, s. 6153-6174
  • Tidskriftsartikel (refereegranskat)abstract
    • Over the past decade, the chemistry of low-valent transition metal clusters has again come to the fore, primarily as a result of the development of nanochemistry and the realization that large clusters are on the cusp of the nano-domain. This perspective focuses on these recent developments in low-valent transition metal cluster chemistry, specifically looking at cluster-nanoparticles, the use of small and medium sized clusters as nanoparticle precursors, the development of clusters as homogeneous catalysts and hydrogen uptake and storage systems, together with fundamental discoveries relating to novel transformations that can take place within the cluster framework.
  •  
42.
  • Hu, Minggang, et al. (författare)
  • Preparation and structures of enantiomeric dinuclear zirconium and hafnium complexes containing two homochiral N atoms, and their catalytic property for polymerization of rac-lactide
  • 2010
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 39:18, s. 4440-4446
  • Tidskriftsartikel (refereegranskat)abstract
    • The hydroxy-and phenoxy-bridged dinuclear zirconium and hafnium complexes 2 and 3 of an amine-pyridine-bis(phenolate) ligand (H2L) were prepared from the reaction of Na2L and ZrCl4 in the presence of 0.5 equiv of water in THF, while the reaction of H2L with NaH and then with ZrCl4 in the freshly distilled THF gave an eight-coordinate bis(homoleptic) mononuclear complex L2Zr (1). Two homochiral N atoms were created in each complex upon coordination of the unsymmetric tertiary amine ligands to the metal centers. Enantiomeric dinuclear complexes 2 and 3 both undergo spontaneous resolution during crystallization. The molecular structure of each enantiomer of 2 and 3, as well as the structure of 1, was determined by X-ray analysis and the circular dichroism spectra of N(R)N(R)-2 and N(S)N(S)-2 were studied. The racemates of 2 and 3 catalyzed controlled polymerization of rac-lactide in terms of the linearity of molecular weight versus conversion, forming isotactic-rich polylactide in high yields with a narrow polydispersity.
  •  
43.
  • Hu, Shichao, et al. (författare)
  • Synthesis and crystal structure of Fe6Ca2(SeO3)(9)Cl-4 - a porous oxohalide
  • 2013
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 42:22, s. 7859-7862
  • Tidskriftsartikel (refereegranskat)abstract
    • A porous oxohalide, Fe6Ca2(SeO3)(9)Cl-4, has been synthesized by solid state reactions using concentrated HCl as the Cl-source. It crystallizes in the hexagonal space group P6(3)/m with unit cell parameters a = 12.118(2) angstrom, c = 12.703(4) angstrom, Z = 2. The crystal structure is an open framework having one-dimensional channels extending along [001] that the chlorine atoms and lone pairs on Se4+ are facing. The channels in this framework structure are unusually large compared to other oxohalide compounds and also accessible to guest molecules. Water vapor sorption measurements show an uptake of 9 wt% at 293 K.
  •  
44.
  • Hu, Shichao, et al. (författare)
  • Synthesis and crystal structure of two synthetic oxofluoride framework compounds - Co2TeO3F2 and Co2SeO3F2
  • 2012
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41:41, s. 12786-12789
  • Tidskriftsartikel (refereegranskat)abstract
    • Two new isostructural Co2+ containing tellurium and selenium oxofluoride compounds Co2TeO3F2 and Co2SeO3F2 are synthesized and their structures determined by single crystal X-ray diffraction. They crystallize in the orthorhombic space group Pnma with the unit cell parameters a = 7.3810(5) angstrom, b = 10.1936(7) angstrom, c = 5.3013(3) angstrom and a = 7.2655(8) angstrom, b = 10.0013(13) angstrom, c = 5.3564(6) angstrom, respectively. The Co(II) ion has octahedral coordination [CoO3F3] and builds up a 3D framework by corner- and edge sharing. The Se(IV) and the Te(IV) ions have the coordinations [SeO3E] and [TeO3E] respectively where E is the lone-pair electrons. The Se(IV) and Te(IV) ions are isolated from each other and bond only to the [CoO3F3] polyhedra. The electronegative element fluorine takes the role of a network builder like oxygen and helps to form the 3D framework structure. This is a difference compared to many oxohalide compounds containing Cl and Br where the halide ions are terminating ions preventing a 3D network from being formed. Long range antiferromagnetic interactions dominate at temperatures < 20 K. The magnetic susceptibility follows the Curie-Weiss law above 25 K with the Curie constant C = 5.62 emu K mol(-1), the Weiss temperature theta = -56 K and the effective magnetic moment mu(eff) = 4.74 mu(B) per cobalt atom.
  •  
45.
  • Huang, Shiliang, 1984-, et al. (författare)
  • SU-75 : a disordered Ge-10 germanate with pcu topology
  • 2012
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41:40, s. 12358-12364
  • Tidskriftsartikel (refereegranskat)abstract
    • A disordered open-framework germanate, denoted as SU-75, was synthesized under hydrothermal conditions using diethylenetriamine (dien) or alternatively 1,4-diaminobutane (dab) as the structure directing agent (SDA). SU-75 crystallizes in a tetragonal space group I-42d(No. 122) with a= 18.145(3) Å and c= 41.701(9) Å. The three-dimensional (3D) framework is built from Ge10(O,OH)28(Ge10) clusters that are connected following the pcu ( primitive cubic) net topology. SU-75 has 10-, 11- and 12-ring channels along the a- and b-axes and channels with alternating 8-, 10-, 12-, 10-ring openings along the c-axis. The framework exhibits a serious disorder, resulted from two possible connectivities between the units of four Ge 10clusters (4Ge10 unit). The chemical formula of SU-75 is |(H2SDA)2(H2O)n|[Ge10O21(OH)2] (SDA = dien or dab,n= 5–6), determined by combining single crystalsynchrotron X-ray diffraction, thermogravimetric analysis (TGA) and CHN elemental analysis. A superoctahedron is introduced to simplify the description of the connectivity of the Ge10 clusters and to illustrate the disorder. This is also used to compare the structure of SU-75 with those of related Ge10 germanates.
  •  
46.
  • Hutchinson, Daniel J., et al. (författare)
  • Tetratopic pyrimidine-hydrazone ligands modified with terminal hydroxymethyl and acryloyl arms and their Pb(II), Zn(II), Cu(II) and Ag(I) complexes
  • 2014
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43:22, s. 8205-18
  • Tidskriftsartikel (refereegranskat)abstract
    • The first tetratopic pyrimidine-hydrazone (pym-hyz) molecular strands containing terminal hydroxymethyl (L1) and acryloyl (L2) functional groups have been synthesised. L1 was produced by step-wise imine condensation reactions, starting with 6-hydroxymethyl-2-pyridinecarboxaldehyde. L2 was then synthesised through the treatment of L1 with acryloyl chloride. NMR spectroscopy and X-ray crystallography showed that the ligands adopted a helical shape, comprised of 1 and 1/3 helical turns. Both L1 and L2 uncoiled upon reaction with an excess amount of Pb(II), Zn(II) and Cu(II) ions, resulting in linear M4LA8 complexes (where M = Pb(II), Zn(II), or Cu(II); L = L1 or L2; and A = ClO4(-), SO3CF3(-) or BF4(-)). Horse-shoe shaped Pb2LA4 complexes were also formed by reacting Pb(II) ions with either L1 or L2 in a 2 : 1 metal to ligand ratio. The addition of Ag(I) ions to either L1 or L2 resulted in Ag2L2A2 double helicates, which were stable in the presence of excess Ag(I). The Pb(II), Zn(II) and Ag(I) complexes were characterised by NMR spectroscopy, while UV-Vis spectroscopy was used to probe the Cu(II) complexes. In addition, X-ray crystallography was used to analyse the linear Pb4L1A8, horse-shoe shaped Pb2L1(ClO4)4, twisted Cu3L2(SO3CF3)6, and double helicate Ag2L12(SO3CF3)2 complexes yielding the structures [Pb4L1(ClO4)7(H2O)]ClO4.4CH3NO2 (1), [Pb4L1(SO3CF3)8]2.6CH3CN.H2O (2), [Pb2L1(ClO4)2(CH3CN)(H2O)](ClO4)2.2CH3CN.C4H10O.H2O (3), [Cu3L2(SO3CF3)3(CH3CN)2(H2O)](SO3CF3)3.2CH3CN.H2O (4) and [Ag2L12](SO3CF3)2.CH3CN.H2O (5), respectively.
  •  
47.
  • Ivanov, S. A., et al. (författare)
  • Neutron diffraction studies and the magnetism of an ordered perovskite : Ba2CoTeO6
  • 2010
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 39:23, s. 5490-5499
  • Tidskriftsartikel (refereegranskat)abstract
    • The complex perovskite Ba2CoTeO6 (BCTO) has been synthesised, and the crystal structure and magnetic properties have been investigated using a combination of X-ray and neutron powder diffraction, electron microscopy and dielectric, calorimetric and magnetic measurements. It is shown that at room temperature this compound adopts the 6L-trigonal perovskite structure, space group P (3) over barm (s.g. 164) (a = 5.7996(1) angstrom, c = 14.2658(3) angstrom). The structure comprises dimers of face-sharing octahedra as well as octahedra which share only vertices with their neighbours. Dielectric measurements indicate a diffuse transition of antiferroelectric nature near 280 K. A long-range antiferromagnetically ordered state has been identified from neutron diffraction and magnetic studies. The magnetic diffraction peaks were registered below the magnetic transition at about 15 K and a possible model for the magnetic structure is proposed. The structural and magnetic features of this compound are discussed and compared with those of other Co-based quaternary oxides adopting the perovskite structure.
  •  
48.
  • Ivanov, S. A., et al. (författare)
  • Structural and magnetic properties of the ordered perovskite Pb2CoTeO6
  • 2010
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 39:46, s. 11136-11148
  • Tidskriftsartikel (refereegranskat)abstract
    • The complex perovskite Pb2CoTeO6 (PCTO) has been prepared as polycrystalline powders by a solid state reaction route, and the crystal structure and magnetic properties have been investigated using a combination of X-ray and neutron powder diffraction, electron microscopy, dielectric, calorimetric and magnetic measurements. It was shown that at room temperature this compound adopts a trigonal perovskite structure, space group R (3) over bar (a = 5.6782(1) angstrom, c = 13.8552(3) angstrom). The compound undergoes a number of temperature-induced phase transitions and adopts four different structures in the temperature range 5 500 K: monoclinic in P2(1)/n (5 < T < 125 K, tilt system (a(+)b(-)b(-))), monoclinic in I2/m (125 < T < 210 K, tilt system (a(0)b(-)b(-))), rhombohedral in R (3) over bar (210 < T < 370 K, tilt system (a(-)a(-)a(-))), and finally cubic in Fm (3) over barm (above 370 K without any tilting). These structural phase transitions are coupled to changes in the dielectric constant and the heat capacity around 210 and 370 K. A long-range antiferromagnetically ordered state has been identified from neutron powder diffraction and magnetic studies at different temperatures. Magnetic diffraction peaks were registered below the transition at about 16 K and a possible model for the magnetic structure is proposed. Possible coexistence of long-range ordering of the electrical dipoles and the magnetic moments at low temperatures making PCTO a potential multiferroic candidate is discussed.
  •  
49.
  • Jarenmark, Martin, et al. (författare)
  • Unsymmetrical dizinc complexes as models for the active sites of phosphohydrolases.
  • 2010
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 39:35, s. 8183-8194
  • Tidskriftsartikel (refereegranskat)abstract
    • The unsymmetrical dinucleating ligand 2-(N-isopropyl-N-((2-pyridyl)methyl)aminomethyl)-6-(N-(carboxylmethyl)-N-((2-pyridyl)methyl)aminomethyl)-4-methylphenol (IPCPMP or L) has been synthesized to model the active site environment of dinuclear metallohydrolases. It has been isolated as the hexafluorophosphate salt H(4)IPCPMP(PF(6))(2).2H(2)O (H(4)L), which has been structurally characterized, and has been used to form two different Zn(ii) complexes, [{Zn(2)(IPCPMP)(OAc)}(2)][PF(6)](2) () and [{Zn(2)(IPCPMP)(Piv)}(2)][PF(6)](2) () (OAc = acetate; Piv = pivalate). The crystal structures of and show that they consist of tetranuclear complexes with very similar structures. Infrared spectroscopy and mass spectrometry indicate that the tetranuclear complexes dissociate into dinuclear complexes in solution. Potentiometric studies of the Zn(ii) : IPCPMP system in aqueous solution reveal that a mononuclear complex is surprisingly stable at low pH, even at a 2 : 1 Zn(ii) : L ratio, but a dinuclear complex dominates at high pH and transforms into a dihydroxido complex by a cooperative deprotonation of two, probably terminally coordinated, water molecules. A kinetic investigation indicates that one of these hydroxides is the active nucleophile in the hydrolysis of bis(2,4-dinitrophenyl)phosphate (BDNPP) enhanced by complex , and mechanistic proposals are presented for this reaction as well as the previously reported transesterification of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP) promoted by Zn(ii) complexes of IPCPMP.
  •  
50.
  • Johnson, Magnus, et al. (författare)
  • Preparation of potentially porous, chiral organometallic materials through spontaneous resolution of pincer palladium conformers
  • 2013
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 42:23, s. 8484-8491
  • Tidskriftsartikel (refereegranskat)abstract
    • Understanding the mechanism by which advanced materials assemble is essential for the design of new materials with desired properties. Here, we report a method to form chiral, potentially porous materials through spontaneous resolution of conformers of a PCP pincer palladium complex ({2,6-bis[(di-t-butyl-phosphino)methyl]phenyl}palladium(II)halide). The crystallisation is controlled by weak hydrogen bonding giving rise to chiral qtz-nets and channel structures, as shown by 16 such crystal structures for X = Cl and Br with various solvents like pentane and bromobutane. The fourth ligand (in addition to the pincer ligand) on palladium plays a crucial role; the chloride and the bromide primarily form hexagonal crystals with large 1D channels, whereas the iodide (presumably due to its inferior hydrogen bonding capacity) forms monoclinic crystals without channels. The hexagonal channels are completely hydrophobic and filled with disordered solvent molecules. Upon heating, loss of the solvent occurs and the hexagonal crystals transform into other non-porous polymorphs. Also by introducing a strong acid, the crystallisation process can be directed to a different course, giving several different non-porous polymorphs. In conclusion, a number of rules can be formulated dictating the formation of hexagonal channel structures based on pincer palladium complexes. Such rules are important for a rational design of future self-assembling materials with applications in storage and molecular recognition.
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