Svetlana G. Kozlova

The First Octahedral Cluster Complexes With Terminal Formate Ligands : Synthesis, Structure, and Properties of K4[Re6S8(HCOO)6] and Cs4[Re6S8(HCOO)6]

The hexarhenium anionic cluster complex with terminal formate ligands [Re6S8(HCOO)6]4- was obtained by the room-temperature reaction between [Re6S8(OH)6]4- and formic acid in an aqueous solution. The cluster was crystallized as a potassium or cesium salt and characterized by X-ray single-crystal diffraction and elemental analyses, IR, 1H NMR, UV/vis, and luminescence spectroscopies. In particular, the emission quantum yield of the potassium salt of the Re6 cluster anion in the solid phase was determined for the first time. The electronic structures of [Re6S8(HCOO)6]4- and [Re6S8(OH)6]4- were also elucidated by DFT calculations.

NOVEL-TYPE CHEMICAL BONDING IN TLF DUE TO 6S2 INERT PAIR ACTIVATION

Abstract The Tl-F and Tl-Tl bonding in α-TlF and s-TlF have been studied from 203, 205Tl and 19F NMR powder data. The off-ionic part of the Tl-Tl and Tl-F interactions is characterized by indirect spin-spin coupling 203Tl-205Tl, 205Tl-19F and thallium and fluorine nuclear magnetic shielding tensors. It is shown that structure distortions of α-TlF and s-TlF are connected with a thallium 6s2 inert pair activation and with a Tl-Tl interaction of previously unnoted type.

Electronic Rearrangements during the Inversion of Lead Phthalocyanine

The mechanism of inversion of lead phthalocyanine (PbPc), possessing a shuttlecock shape, was studied in detail within the bonding evolution theory framework. We have found that reaction pathway calculated using hybrid density functional theory (DFT) method, B3LYP, consists of five structural stability domains, which are connected by four bifurcation points. Reorganization of Pbs basins with pronounced role of core ones is the basis of the catastrophes identified, whereas basins belonging to other atoms are almost not involved in the electronic structure changing. These results provide the new topological picture of processes underlying the conformational transitions of shuttlecock-shaped metal phthalocyanines adsorbed on surfaces.

Selective Two-Step Oxidation of μ2-S Ligands in Trigonal Prismatic Unit {Re3(μ6-C)(μ2-S)3Re3} of the Bioctahedral Cluster Anion [Re12CS17(CN)6]6–

An oxidation of cluster anion [Re(12)CS(17)(CN)(6)](6-) by H(2)O(2) in water has been investigated. It was shown that selective two-step oxidation of bridging μ(2)-S-ligands in trigonal prismatic unit {Re(3)(μ(6)-C)(μ(2)-S)(3)Re(3)} takes place. The first stage runs rapidly, whereas the speed of the second stage depends on intensity of ultraviolet irradiation of the reaction mixture. Each stage of the reaction is accompanied by a change in the solutions color. In the first stage of the oxidation, the cluster anion [Re(12)CS(14)(SO(2))(3)(CN)(6)](6-) is produced, in which all bridging S-ligands are turned into bridging SO(2)-ligands. The second stage of the oxidation leads to formation of the anion [Re(12)CS(14)(SO(2))(2)(SO(3))(CN)(6)](6-), in which one of the SO(2)-ligands underwent further oxidation forming the bridging SO(3)-ligand. Seven compounds containing these anions were synthesized and characterized by a set of different methods, elemental analyses, IR and UV/vis spectroscopy, and quantum-chemical calculations. Structures of some compounds based on similar cluster anions, [Cu(NH(3))(5)](3)[Re(12)CS(14)(SO(2))(3)(CN)(6)]·9.5H(2)O, [Ni(NH(3))(6)](3)[Re(12)CS(14)(SO(2))(3)(CN)(6)]·4H(2)O, and [Cu(NH(3))(5)](2.6)[Re(12)CS(14)(SO(2))(3)(CN)(6)](0.6)[{Re(12)CS(14)(SO(2))(2)(SO(3))(CN)(5)(μ-CN)}{Cu(NH(3))(4)}](0.4)·5H(2)O, were investigated by X-ray analysis of single crystals.

Physical Properties and Structure of Bound Water in Collagen-Type Fibrillar Proteins as Studied by Scanning Calorimetry

The first-order phase transition observed in half (∼50%) of bound water in rat-tail tendon collagen has been studied by a calorimetric technique. The latent heat of transition, the transition temperature, and the specific heat of a high-temperature phase of this subsystem is found to be close to the characteristics of free water. The properties of the other half (∼50%) of bound water in collagen are similar to the properties of zeolite water.

19F and203,205Tl NMR and structural transformations in chain ammonium and thallium hexafluorozirconates and hexafluorohafnates

Unusual structural transformations were observed in ammonium and thallium hexafluorozirconates and hexafluorohafnates at 300–420 K using high-resolution NMR for solids. It was established that at 300–350 K the initial chain structure of these compounds of orthorhombic symmetry undergoes a transition to disordered state, and at higher temperatures it is transformed into an ordered uniaxial structure which is similar to that of trigonal Cs2ZrF6 and Cs2HfF6.

Electronic Switch in the Carbon-Centered [Re12CS17(CN)6]n−Nanocluster

An abrupt change in internuclear Re–Re distances between {Re6} subunits in the carbon-centered [Re12μ6-CS17(CN)6]n−complexes caused by the change of the oxidation state (n = 6, 8) is first theoretically shown to be possibly controlled by an external electric field.13C NMR signal is shown to change over ~400 ppm (~37G) for μ6-C atom together withn. Thereby, the metal cluster [Re12μ6-CS17(CN)6]n−can be considered as a perspective model of a molecular switch.

Unexpected ligand substitutions in the cluster core {Re6Se8}: synthesis and structure of the novel cluster compound Cs11(H3O)[Re6Se4O4Cl6]3·4H2O

The compound Cs11(H3O)[Re6Se4(O)4Cl6]3.4H2O containing a novel cluster core {Re6Se4(O)4} with ordered ligands, where the 4 positions of one face of a Se4(O)4 cube are occupied exclusively by Se atoms and 4 O atoms lie in the opposite face was synthesized via the interaction of solid Re6Se8Br2 with molten KOH.

Solid‐state reaction as a mechanism of 1T ↔ 2H transformation in MoS2 monolayers

Monolayers of molybdenum disulfide MoS2 are considered to be prospective materials for nanoelectronics and various catalytic processes. Since in certain conditions they undergo 1T ↔ 2H phase transitions, studying these phase changes is an urgent task. We present a DFT research of these transitions to show that they can proceed as a solid‐state reaction. Two transition states were discovered with energy barriers 1.03 and 1.40 eV. Sulfur atoms in the transition states are shown to be displaced relative to molybdenum atoms so that a tendency of one structural modification to transform into the other modification is seen. This kind of displacements agrees with electron microscopy data reported earlier. The energy parameters indicate that 1T → 2H reactions are exothermic for both transition states and can possibly proceed in a self‐sustained manner when initially activated by some external energy impact.

Electron structure of iron chalcogenide clusters {Fe(3)Q} from AIM and ELF data: effect of hydrogen atoms on interatomic interactions.

The electronic structure of [Fe(3)(micro(3)-Q)(CO)(9)](2-) and [(micro-H)(2)Fe(3)(micro(3)-Q)(CO)(9)] (Q = S, Se, and Te) complexes is studied with topological methods AIM and ELF. Fe-Fe bonds in [(micro-H)(2)Fe(3)(micro(3)-Q)(CO)(9)] complexes are shown to break down in the presence of H atoms.