| 1. |
- Ali, Sk Imran, et al.
(författare)
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Crystal Structure of the Disordered Non-Centrosymmetric Compound Fe0.43Mo2.56SbO9.5
- 2019
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Ingår i: Crystals. - : MDPI AG. - 2073-4352. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Single crystals of Fe0.43Mo2.56SbO9.5 were obtained by hydrothermal techniques at 230 degrees C. The crystal structure was determined from single crystal X-ray diffraction data. The compound crystallizes in the non-centrosymmetric space group Pc with unit cell parameters a = 4.0003(2) angstrom, b = 7.3355(3) angstrom, c = 12.6985(6) angstrom, = 90 degrees. The crystal structure comprises five crystallographically independent M atoms and one Sb3+ atom, M atoms are of two kinds of partially occupied sites Mo6+ and Fe3+. The building blocks consist of [SbO3O0.5O0.5E] octahedra (E = lone electron pair) and [(Mo/Fe)O-6] octahedra. The M = (Mo, Fe) and O atoms are arranged in a distorted hexagonal 2D-net, not the Sb atoms. The distortion of the net and consequently the symmetry reduction results mainly from the location of the Sb atoms. Disorder manifests itself as a splitting of the metal sites and as a consequent shortening of the Mo-Fe distances. Six (Mo/Fe)O-6 octahedra are connected to form a pseudohexagonal channel. The Sb3+ atom is displaced from the pseudo-six-fold axis.
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| 2. |
- Chábera, Pavel, et al.
(författare)
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A low-spin Fe(iii) complex with 100-ps ligand-to-metal charge transfer photoluminescence
- 2017
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 543:7647, s. 695-699
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Tidskriftsartikel (refereegranskat)abstract
- Transition-metal complexes are used as photosensitizers1, in light-emitting diodes, for biosensing and in photocatalysis2. A key feature in these applications is excitation from the ground state to a charge-transfer state3,4; the long charge-transfer-state lifetimes typical for complexes of ruthenium5 and other precious metals are often essential to ensure high performance. There is much interest in replacing these scarce elements with Earth-abundant metals, with iron6 and copper7 being particularly attractive owing to their low cost and non-toxicity. But despite the exploration of innovative molecular designs6,8,9,10, it remains a formidable scientific challenge11 to access Earth-abundant transition-metal complexes with long-lived charge-transfer excited states. No known iron complexes are considered12 photoluminescent at room temperature, and their rapid excited-state deactivation precludes their use as photosensitizers13,14,15. Here we present the iron complex [Fe(btz)3]3+ (where btz is 3,3′-dimethyl-1,1′-bis(p-tolyl)-4,4′-bis(1,2,3-triazol-5-ylidene)), and show that the superior σ-donor and π-acceptor electron properties of the ligand stabilize the excited state sufficiently to realize a long charge-transfer lifetime of 100 picoseconds (ps) and room-temperature photoluminescence. This species is a low-spin Fe(iii) d5 complex, and emission occurs from a long-lived doublet ligand-to-metal charge-transfer (2LMCT) state that is rarely seen for transition-metal complexes4,16,17. The absence of intersystem crossing, which often gives rise to large excited-state energy losses in transition-metal complexes, enables the observation of spin-allowed emission directly to the ground state and could be exploited as an increased driving force in photochemical reactions on surfaces. These findings suggest that appropriate design strategies can deliver new iron-based materials for use as light emitters and photosensitizers.
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| 3. |
- Chábera, Pavel, et al.
(författare)
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FeII Hexa N-Heterocyclic Carbene Complex with a 528 ps Metal-To-Ligand Charge-Transfer Excited-State Lifetime
- 2018
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 9:3, s. 459-463
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Tidskriftsartikel (refereegranskat)abstract
- The iron carbene complex [FeII(btz)3](PF6)2 (where btz = 3,3′-dimethyl-1,1′-bis(p-Tolyl)-4,4′-bis(1,2,3-Triazol-5-ylidene)) has been synthesized, isolated, and characterized as a low-spin ferrous complex. It exhibits strong metal-To-ligand charge transfer (MLCT) absorption bands throughout the visible spectrum, and excitation of these bands gives rise to a 3MLCT state with a 528 ps excited-state lifetime in CH3CN solution that is more than one order of magnitude longer compared with the MLCT lifetime of any previously reported FeII complex. The low potential of the [Fe(btz)3]3+/[Fe(btz)3]2+ redox couple makes the 3MLCT state of [FeII(btz)3]2+ a potent photoreductant that can be generated by light absorption throughout the visible spectrum. Taken together with our recent results on the [FeIII(btz)3]3+ form of this complex, these results show that the FeII and FeIII oxidation states of the same Fe(btz)3 complex feature long-lived MLCT and LMCT states, respectively, demonstrating the versatility of iron N-heterocyclic carbene complexes as promising light-harvesters for a broad range of oxidizing and reducing conditions.
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| 4. |
- Doverbratt, Isa, et al.
(författare)
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Linear Metal Chains in Ca2M2X (M = Pd, Pt; X = Al, Ge): Origin of the Pairwise Distortion and Its Role in the Structure Stability
- 2015
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 27:1, s. 304-315
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Tidskriftsartikel (refereegranskat)abstract
- A series of four new analogue phases Ca2M2X (M = Pd, Pt and X = Al, Ge) were prepared by direct combination of the respective elements in stoichiometric mixtures at high temperature in order to analyze the impact of valence electron count (vec) and electronegativity differences (Delta chi) on the structure selection and stability. Their crystal structures, as determined from single-crystal X-ray diffraction data, correspond to two different but closely related structure types. The first compound, Ca2Pd2Ge (I), is an unprecedented ternary ordered variant of the Zr2Al3-type (orthorhombic, Fdd2). The three other phases, Ca2Pt2Ge (II), Ca2Pd2Al (III) and Ca2Pt2Al (IV), adopt the Gd2Ge2Al-type structure (monoclinic, C-2/c). All title structures feature linear chains of the noble metals (Pd or Pt). The Pd linear chains in I are undistorted with equidistant Pd center dot center dot center dot Pd atoms, whereas the metal chains in II-IV are pairwise distorted, resulting in short connected {Pd-2} or {Pt-2} dumbbells that are separated by longer M center dot center dot center dot M contacts. The occurrence and magnitude of the pairing distortion in these chains are controlled by the vec and the Delta chi between the constituent elements, a result which is supported by analysis of the calculated Bader effective charges. The metal chains act as charge modulation units, critical for the stability and the electronic flexibility of the structures by an adequate adjustment of the metal-metal bond order to both the vec and the degree of charge transfer. Thus, Ca2Pd2Ge (28 ve/f.u) is a Zintl-like, charge optimized phase with formally zerovalent Pd atoms forming the undistorted metal chains; semimetallic properties are predicted by TB-LMTO calculations. In contrast, the isoelectronic Ca2Pt2Ge is predicted to be a good metal with the Fermi level located at a local maximum of the DOS, a fingerprint of potential electronic instability. This is due to greater charge transfer to the more electronegative Pt atoms forming the metal chains and probably to packing frustration in the well packed structure that may prevent a larger distortion of the Pt chains. However, the instability is suppressed in the aliovalent but isostructural phases Ca2M2Al (27 ve/f.u) with an enhancement of the pairing distortion within the metal chains but lower M-M bond order. Further reduction of the vec as in Ca2M2Cd (26 ve/f.u) may induce a transition toward the more geometrically flexible W2CoB2-type with a low dimensional structure, to create more room for a larger distortion of the metal chain as dictated by the shortage of valence electrons.
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| 5. |
- Doverbratt, Isa, et al.
(författare)
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Synthesis, Crystal Structure, and Bonding Analysis of the Hypoelectronic Cubic Phase Ca5Pd6Ge6.
- 2015
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 1520-510X .- 0020-1669. ; 54:18, s. 9098-9104
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Tidskriftsartikel (refereegranskat)abstract
- The title compound, Ca5Pd6Ge6, was obtained during a systematic investigation of the Ca-Pd-Ge ternary phase diagram. The crystal structure was determined and refined from single-crystal X-ray diffraction data. It crystallizes in a new structure variant of the Y4PdGa12-type structure (Im3̅m, a = 8.7764(4) Å) that features an arrangement of vertex-sharing body-centered cubes of calcium, Ca@Ca8, with a hierarchical bcc network, interpenetrating a second (Pd6Ge6) network consisting of Ge2 dumbbells surrounded by Pd in a strongly flattened octahedron with Pd(μ(2)-η(2),η(4)-Ge2)-like motifs. These octahedra are condensed through the Pd to form a 3D open fcc network. Theoretical band structure calculations suggested that the compound is hypoelectronic with predominantly multicenter-type interatomic interactions involving all three elements and essentially a Hume-Rothery-like regime of electronic stabilization. The similar electronegativity between germanium and palladium atoms has a decisive impact on the bonding picture of the system.
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| 6. |
- Ekengard, Erik, et al.
(författare)
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Antimalarial activity of ruthenium(ii) and osmium(ii) arene complexes with mono- and bidentate chloroquine analogue ligands.
- 2015
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 44:44, s. 19314-19329
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Tidskriftsartikel (refereegranskat)abstract
- Eight new ruthenium and five new osmium p-cymene half-sandwich complexes have been synthesized, characterized and evaluated for antimalarial activity. All complexes contain ligands that are based on a 4-chloroquinoline framework related to the antimalarial drug chloroquine. Ligands are salicylaldimine derivatives, where = N-(2-((2-hydroxyphenyl)methylimino)ethyl)-7-chloroquinolin-4-amine, and contain non-hydrogen substituents in the 3-position of the salicylaldimine ring, viz. F, Cl, Br, I, NO2, OMe and (t)Bu for , respectively. Ligand is also a salicylaldimine-containing ligand with substitutions in both 3- and 5-positions of the salicylaldimine moiety, i.e. N-(2-((2-hydroxy-3,5-di-tert-butylphenyl)methyl-imino)ethyl)-7-chloroquinolin-4-amine, while is N-(2-((1-methyl-1H-imidazol-2-yl)methylamino)ethyl)-7-chloroquinolin-4-amine) The half sandwich metal complexes that have been investigated are [Ru(η(6)-cym)()Cl] (Ru--Ru-, cym = p-cymene), [Os(η(6)-cym)()Cl] (Os--Os-, Os-, and Os-), [M(η(6)-cym)()Cl2] (M = Ru, Ru-; M = Os, Os-) and [M(η(6)-cym)()Cl]Cl (M = Ru, Ru-; M = Os, Os-). In complexes Ru--Ru- and Ru-, Os--Os-, Os- and Os- and Os-, the ligands were found to coordinate as bidentate N,O- and N,N-chelates, while in complexes Ru- and Os-, monodentate coordination of the ligands through the quinoline nitrogen was established. The antimalarial activity of the new ligands and complexes was evaluated against chloroquine sensitive (NF54 and D10) and chloroquine resistant (Dd2) Plasmodium falciparum malaria parasite strains. Coordination of ruthenium and osmium arene moieties to the ligands resulted in lower antiplasmodial activities relative to the free ligands, but the resistance index is better for the ruthenium complexes compared to chloroquine. Overall, osmium complexes appeared to be less active than the corresponding ruthenium complexes.
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| 7. |
- Folkers, Laura C., et al.
(författare)
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The Mystery of the AuIn 1 : 1 Phase and Its Incommensurate Structural Variations
- 2018
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 57:5, s. 2791-2796
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Tidskriftsartikel (refereegranskat)abstract
- In this communication, the AuIn 1:1 phase (Naturwissenschaften, 1953, 40, 437, DOI: 10.1007/BF00590353), and its ordering behavior at various temperatures is investigated. To enable the growth of a X-ray suitable specimen, a tempering routine was established by the interpretation of a differential scanning calorimetry (DSC) study. In this way, good quality single crystals were grown and measured at the Crystal beamline at Synchrotron SOLEIL. From the acquired data, three variations of this structure could be found at temperatures of 400 °C and 300 °C and room temperature, with differing degrees of incommensurate modulation. Diffuse scattering found at 400 °C was interpreted with the help of a three-dimensional difference pair distribution function (3D-ΔPDF) study.
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| 8. |
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From a grain of salt to the ribosome : the history of crystallography as seen through the lens of the Nobel Prize
- 2015
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- This book is published to celebrate the International Year of Crystallography 2014, as proclaimed by the United Nations. The year has been chosen as the International Year of Crystallography since it was 100 years ago that the first Nobel Prize was awarded for crystallographic observations to Max von Laue. Just a year later, Sir William Henry Bragg and William Lawrence Bragg, father and son, won their prize for showing the possibility of determining atomic positions in crystals. This book describes the lives and works of 33 Nobel Laureates starting with Wilhelm Conrad Röntgen (1901) and ending with Brian Kobilka (2012). It also reproduces the most important works of these scientists. The book gives a historical perspective of a scientific field that is important for our understanding of the atomic organization of the world around us, from inorganic materials to complex biological molecules, such as the ribosome.
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| 9. |
- Jana, Manoj K., et al.
(författare)
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Resolving Rotational Stacking Disorder and Electronic Level Alignment in a 2D Oligothiophene-Based Lead Iodide Perovskite
- 2019
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 31:20, s. 8523-8532
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) represent diverse quantum well heterostructures composed of alternating inorganic and organic layers. While 2D HOIPs are nominally periodic in three dimensions for X-ray scattering, the inorganic layers can orient quasi-randomly, leading to rotational stacking disorder (RSD). RSD manifests as poorly resolved, diffuse X-ray scattering along the stacking direction, limiting the structural description to an apparently disordered subcell. However, local ordering preferences can still exist between adjacent unit cells and can considerably impact the properties, particularly the electronic structure. Here, we elucidate RSD and determine the preferred local ordering in the 2D [AE2T]PbI4 HOIP (AE2T: 5,5′-bis(ethylammonium)-[2,2′-bithiophene]). We use first-principles calculations to determine energy differences between a set of systematically generated supercells with different order patterns. We show that interlayer ordering tendencies are weak, explaining the observed RSD in terms of differing in-plane rotation of PbI6 octahedra in neighboring inorganic planes. In contrast, the ordering preference within a given organic layer is strong, favoring a herringbone-type arrangement of adjacent AE2T cations. The calculated electronic level alignments of proximal organic and inorganic frontier orbitals in the valence band vary significantly with the local arrangement of AE2T cations; only the most stable AE2T configuration leads to an interfacial type-Ib band alignment consistent with observed optical properties. The present study underscores the importance of resolving local structure arrangements in 2D HOIPs for reliable structure-property prediction.
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| 10. |
- Jana, Partha, et al.
(författare)
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AuCd4: A Hume-Rothery Phase with VEC of 1.8 and Icosahedral and Trigonal-Prismatic Clusters as Building Blocks.
- 2015
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 1520-510X .- 0020-1669. ; 54:3, s. 713-721
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Tidskriftsartikel (refereegranskat)abstract
- The η phase in the Au-Cd binary system has been synthesized, and the structure has been analyzed by single-crystal X-ray diffraction. The compound η-AuCd4 crystallizes in the hexagonal space group P63/m (No. 176). The unit cell contains ∼273 atoms. The compound AuCd4 represents a √3a × √3a × c superstructure of the AgMg4 type. The structure can be well described by icosahedral and trigonal-prismatic clusters. A phase transition to the high-temperature ε phase occurs exothermically at around 578 K. The compound is formed at a sharp valence electron concentration of 1.8 e/a. The compound can be understood within the framework of the Hume-Rothery stabilization mechanism.
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