| 1. |
- Abbasi, Alireza, et al.
(författare)
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Ambidentate coordination of dimethyl sulfoxide in rhodium(III) complexes
- 2011
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 40:5, s. 1111-1118
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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)
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Potassium ion-mediated non-covalent bonded coordination polymers
- 2012
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41:3, s. 850-859
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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)
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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
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43, s. 3939-3948
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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)
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Electronic structure and catalytic aspects of [Ru(tpm)(bqdi)(Cl/H2O)]n, tpm = tris(1-pyrazolyl)methane and bqdi = o-benzoquinonediimine
- 2013
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 42, s. 3721-3734
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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)
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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
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43, s. 13932-13947
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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)
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Allylic alcohols as synthetic enolate equivalents : Isomerisation and tandem reactions catalysed by transition metal complexes
- 2012
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41:6, s. 1660-1670
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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)
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Synthesis and characterization of a ferrocene-linked bis-fullerene[60] dumbbell
- 2012
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Ingår i: Dalton Transactions. - 1477-9226 .- 1477-9234. ; 41:8, s. 2374-2381
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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)
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Ion pumps as biological targets for decavanadate
- 2013
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 42:33, s. 11770-11777
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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)
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Speciation and structure of tin(II) in hyper-alkaline aqueous solution
- 2014
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43, s. 17971–17979-
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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)
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Speciation and the structure of lead(II) in hyperalkaline aqueous solution
- 2014
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43, s. 17539-17543
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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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