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We present a unique new subclass of Cu(i) hybrid complexes, showing TADF with near-unity quantum yields as well as unprecedented solvatochromic emission and strong X-ray radioluminescence.

Four novel rhenium cluster complexes with the general formula trans-[Re6Q8(ppy)4X2]·n(ppy) (Q = S, Se; X = Cl, Br; ppy = 4-phenylpyridine) are obtained by the interaction of salts Csn[Re6Q8X6]·2H2O (Q = S, n = 4; Q = Se, n = 3; X = Cl or Br) with a 4-phenylpyridine melt. The single-crystal XRD study shows that the structures of these compounds contain molecular fragments trans-[Re6Q8(ppy)4X2] packed together with 4-phenylpyridine solvate molecules and connected with these molecules by weak interactions, including hydrogen bonds and π-stacking of aromatic rings. It is shown that different halide and chalcogenide ligands of the cluster complex form different types of packing. The obtained compounds are insoluble in water and in organic solvents. The crystal samples are luminescent in the red region with emission peaks at 708-718 nm, quantum yields of 0.01-0.03, and emission lifetimes of ~ 4 μs. The electronic structure of these compounds contains ligand-centered LUMO–LUMO+3 levels localized between metal-centered HOMO and LUMO+4 levels.

Bi3+ and Pb2+ uptake by a monolacunary Keggin-type [PW11O39]7- anion leads to the formation of [PW11O39Bi]4- and [PW11O39Pb]5- complexes with a stereochemically active lone pair at the incorporated heterometal. The two complexes were isolated as (TBA)4[PW11O39Bi] (1) and (TBA)5[PW11O39Pb] (2) and characterized by 31P and 183W NMR spectroscopy, high-resolution electrospray mass-spectrometry (HR-ESI-MS) and cyclic voltammetry (CV). EXAFS and XANES data confirm the unchanged oxidation state and ψ-square pyramidal geometry of Bi3+ and Pb2+ in 1 and 2. DFT calculations were used in order to (i) confirm the absence of ligands attached to the heterometal sites in both complexes and localize the lone pair, and (ii) assign all signals in the 183W NMR spectra. Complexes 1 and 2 demonstrate photoluminescence (PL). A reversible change in the PL spectra of both complexes in the presence of water vapor has been detected. On the contrary, PL data for sandwich-type ((CH3)4N)4K3[H4(PW11O39)2Bi]·25H2O (3) do not show sensitivity to water vapor.

A suite of paddle-wheel shaped [Cu2(PymPPh2)3(Lan)n](PF6)2 complexes showing efficient thermally activated delayed fluorescence (TADF) has been synthesized. In these complexes, Cu(I) ions are P,N-bridged by three diphenyl(2-pyrimidyl)phosphine (PymPPh2, L) ligands in a "head-to-tail" fashion, and one or both metals are also capped by the ancillary ligand (Lan = MeOH, Me2CO, MeCN, PhCN). At ambient temperature, the solid complexes emit TADF with the quantum yield of up to 85% and the lifetimes of from 9.6 to 27 μs. The ancillary ligands, whose orbitals negligibly contribute to the radiative 1(M + L + Lan)LCT state, remarkably adjust emission energies and ΔE(S1-T1) energy splitting magnitudes of the emitters obtained. Thus, depending on structure and/or number of the Lan molecules, the emission maxima vary from 500 to 563 nm, and the ΔE(S1-T1) gaps range 550-1100 cm-1. Such tunable TADF characteristics coupled with the excellent solubility and air-stability make the complexes presented to be promising TADF materials.

The electronic structure of heterometallic cubane-type clusters with core {Mo3S4M′} (M′ = Cu+, Ni0, Pd0) was investigated by the Atoms in Molecules and Electron Localization Function topological methods as well as Energy Decomposition Analysis. It was found that {Mo3S4Cu} and {Mo3S4M′} (M′= Ni, Pd) clusters have a different interaction between molybdenum and heterometallic atoms. In case of the complexes with Ni/Pd atom, the disynaptic basins on the Mo–M′ bonds were observed in contrast to the Cu containing complex. The complex formation between heterometallic fragments and trinuclear molybdenum complex {Mo3S4} were found to be hindered due to steric interactions. Nevertheless, the formation of the heterometallic cubane-type clusters occurs due to the multicenter and pair covalent interactions between Mo and M′ atoms.

It is shown by the methods of quantum chemistry that Zn2(BDC)2DABCO crystals are formed due to covalent and dispersion interactions between two-dimensional Zn2(BDC)2 layers and DABCO molecules. The crystals contain chiral pseudo one-dimensional chains composed only of left-twisted or right-twisted DABCO molecules and {Zn2(O2C)4} fragments arranged parallel to the vector c of the Zn2(BDC)2DABCO crystal.

Influence of the metal core composition and geometry on the structure, spectroscopic properties and redox potentials was investigated for the first time for heterometallic (Re/Mo)6 octahedral clusters. The discrete anionic clusters [Re6-x Mox Se8 (CN)6 ]n- (x=2, 3; n=4, 5) were obtained as individual salts. Their isomeric composition and bond-length distribution were inspected using a combination of single-crystal X-ray structure analysis, NMR, EXAFS, and DFT calculations.

The energy and structural parameters were obtained for all forms of the carbonyl complex of osmium Os3(CO)12 with D3h and D3 symmetries using density functional theory (DFT) methods. The calculations took into account various levels of relativistic effects, including those associated with nonconservation of spatial parity. It was shown that the ground state of Os3(CO)12 corresponds to the D3 symmetry and thus may be characterized either as left-twisted (D3S) or right-twisted (D3R). The D3S↔D3R transitions occur through the D3h transition state with an activation barrier of ~10–14 kJ/mol. Parity violation energy difference (PVED) between D3S and D3R states equals to ~5 × 10−10 kJ/mol. An unusual three-center exchange interaction was found inside the {Os3} fragment. It was found that the cooperative effects of the mutual influence of osmium atoms suppress the chirality of the electron system in the cluster.

The heterometallic cluster-based compound K

(Rhodium trichloride reacts with 1,2-bis[(2,6-diisopropylphenyl)imino] acenaphthene (dpp-bian) to afford new octahedral complex mer-[Rh(dpp-bian)(H2O)Cl3]·CH2Cl2. The CV of mer-[Rh(dpp-bian)(H2O)Cl3] in MeCN shows an irreversible reduction that corresponds to the RhIII/RhI couple, followed by reversible or quasi-reversible cathodic waves assigned to reduction of the dpp-bian ligand. DFT calculations confirm the assignment of the redox processes and predict the elimination of two chloride ligands from axial positions upon two-electron reduction of mer-[Rh(dpp-bian)(H2O)Cl3] with the formation of a RhI square-planar complex [RhI(dpp-bian)(H2O)Cl].

International audience; A number of transition metal cluster compounds can be obtained only in the melt of inorganic cyanides and, therefore, contain terminal cyanide ligands. Substitution of these ligands, which is often necessary to change the physicochemical properties of the clusters, is an urgent problem because of their low reactivity in substitution reactions. In this work, a synthetic approach has been developed for the substitution of CN-ligands in the heterometallic cluster anions [Re(3)Mo(3)Q(8)(CN)(6)](n-) (Q = S, n = 6; Q = Se, n = 5) by the 4-tert-butylpyridine (TBP) molecules. Two new compounds, namely [Re3Mo3S8(TBP)(6)] (1) and [Re3Mo3Se8(TBP)(6)] (2), were obtained with high yields and crystallized under solvothermal conditions. It has been shown that compounds 1 and 2 are based on the paramagnetic cluster cores {Re(3)Mo(3)Q(8)}(0) containing 23 cluster valence electrons (CVE). The geometry of the new compounds has been investigated using X-ray structural analysis. The electronic structure has been analyzed using the DFT calculations showing large distortion of M-6 cluster core.

The first observation of luminescence from Ag(I) complexes with a square-planar geometry of the metal is reported. [Ag(Py3PO)2]ClO4 and [Ag(Py3PO)2]OTf – first examples of the emissive square-planar Ag(I) complexes – have been synthesized by the reaction of tris(2-pyridyl)phosphine oxide (Py3PO) with Ag(I) salts. Both complexes exhibit pronounced photoluminescence in the solid state at ambient temperature with nano- and microsecond lifetime components. Remarkably, the luminescence of the complexes has a reversible thermochromic behavior, changing their emission color from yellow (λemmax ≈ 585 nm) at room temperature to red-orange (λemmax = 620 nm) at 77 K. The spectroscopic and computational results reveal that the emission of the title compounds can be assigned to the 3MLCT phosphorescence with admixture of the 1MLCT fluorescence.

The review reports recent progress in experimental and theoretical studies of structure and properties of the C6H12N2 molecule (DABCO) in metal-organic frameworks M2(C8H4O4)2 C6H12N2, where M = Co, Ni, Cu, Zn (M-DMOFs), as well as in the gas and crystalline phases. M-DMOFs belong to a new class of compounds which are considered promising materials for sorption, catalysis, selective separation, and demonstrate other remarkable properties. We review recent research on phase transitions and effect of guest molecules on properties of M-DMOFs. Thermodynamic and nuclear magnetic resonance studies of M-DMOFs indicate quantum tunneling between twisted forms (chiral isomers) of the DABCO molecule with D3 symmetry, which stops at certain low temperature. This opens an opportunity for study and control of balance between chiral isomers.

International audience; Among the great amount of known lanthanide nanoparticles, reports devoted to chalcogenide ones are deficient. The properties of such nanoparticles remain almost unknown due to the lack of simple and proper synthetic methods avoiding hydrolysis and allowing preparation of oxygen-free lanthanide nanoparticles. A liquid exfoliation method was used to select the optimum strategy for the preparation of quaternary lanthanide sulfide nanoparticles. Bulk KLn(2)CuS(6) (Ln = La-Sm) materials were obtained via a reactive flux method. The crystal structures of three new members of the KLn(2)CuS(6) series were determined for Pr, Nd, and Sm as well as for known KLa2CuS6. KLn(2)CuS(6) (Ln = La, Pr, Nd) compounds crystallize in the monoclinic C2/c space group, whereas KSm2CuS6 crystallizes in the orthorhombic Fddd space group. The analysis of their electronic structures confirms that the main bonding interactions occur within the anionic {Ln(2)CuS(6)}(-) layers. Due to their layered structure, exfoliation of these compounds is possible using ultrasonic treatment in appropriate solvents with the formation of colloidal solutions. Colloidal particles show a plate-like morphology with a lateral size of 100-200 nm and a thickness of 2-10 nm. Highly negative or positive charges found in isopropanol and acetonitrile dispersions, respectively, are associated with high stability and concentration of the dispersions.

The optical properties of metal-organic frameworks [M

Substitution of terminal halide ligands of octahedral rhenium cluster complexes [Re6Q8X6]4– in a melt of 4,4′-bipyridine (bpy) led to us obtaining four new compounds with the general formula trans-...

A first method for obtaining of electron-rich bioctahedral rhenium clusters has been developed. Two cluster salts, namely (Et3NH)4(Me2NH2)4[Re12CS14(µ-S)3Cl6] (1) and (Et4N)4(Me2NH2)4[Re12CS14(µ-S)3Br6] (2), have been synthesized and isolated in the solid state. Single-crystal X-ray diffraction showed that salts 1 and 2 are based on the new cluster anions [Re12CS14(µ-S)3Cl6]8− and [Re12CS14(µ-S)3Br6]8− containing 48 cluster valence electrons (CVE). The correlations between geometry and CVE number of the bioctahedral chalcohalide anions have been examined using the DFT calculations. The dissolution of the salts 1 and 2 is accompanied by the oxidation yielding the [Re12CS14(µ-S)3Cl6]6− and [Re12CS14(µ-S)3Br6]6− anions. Properties of the new clusters in the DMSO solutions have been investigated by UV–Vis spectroscopy and cyclic voltammetry. The latter revealed the presence of multiple reversible one-electron redox waves in a narrow potential window.

Cluster compounds based on a new {Re3Mo3Se8}n core were obtained and studied. The polymeric solid K6[Re3Mo3Se8(CN)4(CN)2/2] (1) containing 24 cluster valence electrons (CVE) was isolated as a result of high-temperature reaction. Water-soluble salts K5[Re3Mo3Se8(CN)6]·11H2O (2) and Cs5[Re3Mo3Se8(CN)6]·H2O (3) were prepared from compound 1. Crystal structures of the diamagnetic compounds 2 and 3 contain a cluster anion [Re3Mo3Se8(CN)6]5- with a 22-electronic core {Re3Mo3Se8}+. Metathesis reaction followed by recrystallization from CH3CN yielded paramagnetic salt (Ph4P)4[Re3Mo3Se8(CN)6]·2CH3CN (4) containing the {Re3Mo3Se8}2+ core with 21 CVE. Cyclic voltammetry of the solution of 4 displayed three quasi-reversible waves with E1/2 = -0.325, -0.818 and -1.410 V vs. Ag/AgCl electrode indicating the presence of [Re3Mo3Se8(CN)6]4-/5-/6-/7- transitions. Electronic structure calculations showed that both mer- and fac-isomers of [Re3Mo3Se8(CN)6]n- clusters undergo great distortion when the number of CVE decreases.

A family of brightly luminescent dinuclear complexes of [Cu(μ2-X)(N^N)]2 type (X = I or SCN) has been synthesized in 76–90% yields by the reaction of bis(2-pyridyl)phosphine oxides (N^N) with the corresponding Cu(I) salts. The X-ray diffraction study reveals that the Cu2I2 core of the [Cu(μ2-I)(N^N)]2 complexes has either a butterfly- or rhomboid-shaped structure, while the eighth-membered [Cu(SCNNCS)Cu] ring in the [Cu2(SCN)2(N^N)]2 complexes is nearly planar. In the solid state, these compounds exhibit a strong green-to-yellow emission (λemmax = 536–592 nm) with high PLQYs (up to 63%) and short lifetimes (1.9–10.0 μs). The combined photophysical and DFT study indicates that the ambient-temperature emission of the complexes obtained can be assigned to the thermally activated-delayed fluorescence (TADF) from the 1(M + X)LCT excited state, while at 77 K, phosphorescence from the 3(M + X)LCT state is likely observed.

Interatomic interactions in M 2 (C 8 H 4 O 4 ) 2 C 6 H 12 N 2 (M = Co, Ni, Cu, Zn) metal-organic framework polymers have been studied with the methods of quantum chemistry and X-ray photoelectron spectroscopy. Interactions of C 6 H 12 N 2 molecules and C 8 H 4 O 4 2− anions with metal atoms are shown to be of closed-shell type. C 6 H 12 N 2 molecules are positively charged, the value of the charge slightly depends on the type of the metal atoms. M M interactions are described as “intermediate interactions” with some covalence contribution which reaches maximum for the interactions between cobalt atoms. The obtained quantum-chemical data agree with those obtained from photoelectron spectroscopy measurements.

The quantum chemical calculations of induced electric currents in (μ-H)2Fe3(μ3-Q)(CO)9 complexes, where Q = S, Se, Te, are carried out. It is demonstrated that the appearance of anomalous 1Н NMR chemical shifts on bridging hydrogen atoms is, first of all, due to the effect of induced currents on iron atoms.

For the first time the comparison of the theoretical and experimental data have shown that UV–vis absorption in the region of 600 nm in colloidal solution of NbS 3 can be described by the d-d electronic transitions to the antibonding molecular orbital. It is proved that the process leads to excitation of metal-metal bond.

The reduction of tetraphenyldiphosphine with two differently substituted samarocenes(II) proceeds via different pathways. With [SmCp*2(THF)2] (Cp* = η5-C5Me5), the reaction had been known to result in the THF ring-opening product, [SmCp*2(O(CH2)4PPh2)], 3, owing to the instability of phosphido complex [SmCp*2(PPh2)] in the presence of THF. Complex 3 crystallizes from apolar solvents as dimeric or polymeric polymorph with butoxo-phosphine bridging ligands in both cases. In contrast, the phosphide [SmCp″2(PPh2)] (Cp′′ = η5-1,3-C5H3tBu2), 5, is not prone to ring-opening owing to insufficient space in the Sm coordination sphere for a THF ligand. Product 5 is inevitably accompanied by homoleptic complex [SmCp″3] 6 and dinuclear mixed-valent complex [SmIIICp″2(μ-PPh2)2SmIICp″] 7 as the further products of redox transformations and ligand exchange. The formation of 5–7 is rationalized by a sequence of initial coordination of one or two {SmIICp″2} fragments by P atoms and reductive elimination of PPh2· or Cp″· ra...

The energy and structural parameters of 1,4-diazabicyclo[2.2.2]octane (DABCO) obtained by various DFT methods are examined versus ab initio and experimental data. The features of twisting potentials of DABCO and closely-related species (1-azabicyclo[2.2.2]octane and bicyclo[2.2.2]octane) are discussed in light of computational schemes applied.

The first luminescent twelve-nuclear rhenium cluster complexes were obtained. Three new clusters, namely, [Re12CS14(μ-Cl)3Cl6]5-, [Re12CS14(μ-Br)3Cl6]5- and [Re12CS14(μ-Br)3Br6]5-, were synthesized using the non-isovalent substitution of μ-O ligands within the {Re12CS14(μ-O)3}0 cluster core by halide anions. The geometry of the new clusters was investigated by X-ray structural analysis, and the electronic structures were evaluated by the use of DFT calculations. It was found that compounds based on these anions showed red luminescence in both the solid state and solution that was never observed before for previously studied twelve-nuclear rhenium clusters.

Cubane-type Mo

Influence of the metal core composition and geometry on the structure, spectroscopic properties and redox potentials was investigated for the first time for heterometallic (Re/Mo)

Structural parameters and energies of secondary building units (SBUs) in Zn2(C8H4O4)2·C6H12N2 have been examined with DFT and CCSD(T) methods. The SBU structure exhibits flexibility due to close energies of formation of its D4h, D4, and D2d forms. The potential energy surfaces (PESs) calculated for these systems testify that the presence of pillar ligands with negatively charged nitrogens (NCH or DABCO) can lead to almost barrier-free transitions between structural SBU forms. The mobility regions of the SBU motif have been determined.

Cubane-type Mo3S4 cluster hydrides decorated with phosphine ligands are active catalysts for the transfer hydrogenation of nitroarenes to aniline derivatives in the presence of formic acid (HCOOH) and triethylamine (Et3N). The process is highly selective and most of the cluster species involved in the catalytic cycle have been identified through reaction monitoring. Formation of a dihydrogen cluster intermediate has also been postulated based on previous kinetic and theoretical studies. However, the different steps involved in the transfer hydrogenation from the cluster to the nitroarene to finally produce aniline remain unclear. Herein, we report an in-depth computational investigation into this mechanism. Et3N reduces the activation barrier associated with the formation of Mo–HHOOCH dihydrogen species. The global catalytic process is highly exergonic and occurs in three consecutive steps with nitrosobenzene and N-phenylhydroxylamine as reaction intermediates. Our computational findings explain how hydrogen is transferred from these Mo–HHOOCH dihydrogen adducts to nitrobenzene with the concomitant formation of nitrosobenzene and the formate substituted cluster. Then, a b-hydride elimination reaction accompanied by CO2 release regenerates the cluster hydride. Two additional steps are needed for hydrogen transfer from the dihydrogen cluster to nitrosobenzene and N-phenylhydroxylamine to finally produce aniline. Our results show that the three metal centres in the Mo3S4 unit act independently, so the cluster can exist in up to ten different forms that are capable of opening a wide range of reaction paths. This behaviour reveals the outstanding catalytic possibilities of this kind of cluster complexes, which work as highly efficient catalytic machines.

Among the great amount of known lanthanide nanoparticles, reports devoted to chalcogenide ones are deficient. The properties of such nanoparticles remain almost unknown due to the lack of simple and proper synthetic methods avoiding hydrolysis and allowing preparation of oxygen-free lanthanide nanoparticles. A liquid exfoliation method was used to select the optimum strategy for the preparation of quaternary lanthanide sulfide nanoparticles. Bulk KLn

The influence of magnetic fields on the properties of chiral molecules is of great interest nowadays. This work presents an (1)H NMR study of the mobility of 1-phenylethanol and 1-phenyl-1-propanol molecules in pure forms and in chirally polarized mixtures in external magnetic fields. Molecular mobility is shown to be dependent on the strength of the external magnetic field and chiral mixing. It could be assumed that the mobility changes are caused by rotational and magnetic interactions between induced magnetic moments of the aromatic molecules and the external magnetic field; intermolecular interactions are also essential. The results are important for the tasks related to enantiomer separation.

The review presents the experimental and theoretic data on relativistic effects in solids, which were the objects of S. P. Gabuda’s studies. Coordination and cluster compounds are considered. Unique data obtained by nuclear magnetic resonance, vibrational spectroscopy, magnetochemistry and other methods are presented. The possibilities of the occurrence of polymorphic phase transitions, the Jahn–Teller effect, intermolecular interactions, and other effects due to the features of structure of relativistic wave functions are discussed.

The reaction of cluster [Re3S4(Dppe)3Br3]Br with sodium tert-butyl thiolate affords trinuclear cationic cluster [Re3S5(Dppe)3]Br (I). The oxidation of cluster I with air gives [Re3S4(SO2)(Dppe)3]Cl (II), which is characterized by X-ray diffraction analysis in the form of solvate II · 3.5CH2Cl2 (CIF file CCDC 1401732). The DFT calculations indicate the triplet ground state of the [Re3S5(Dppe)3]+ cation and a significant spin density on the equatorial sulfide ligands, favoring the oxidation of the cluster.

Experimental evidences are first obtained to demonstrate the effect of external magnetic field on the mobility of 1-phenylethanol molecules characterized by conjugated ring bonds. Enantiomers of these molecules are shown to have different mobilities in chiral polarized mediums composed of these enantiomers taken in various proportions. The difference diminishes when the external magnetic field increases.

W W and W X bonds in a series of trigonal prismatic [X@W6Cl18]n (n = 0, −2, −4 for X = C; n = 1, −1, −3 for X = N) clusters were studied using the methods of Electron Localization Function (ELF) and the Atoms In Molecules (AIM) along with the molecular orbital (MO) approach. The [X@W6Cl18]n clusters contain two {W3} fragments which form a trigonal prism. Each {W3} fragment is characterized by a three-center bond and three two-center bonds. The carbon or the nitrogen atom encapsulated in the center of the trigonal prism influence intertriangular W W bonds. The bonding pattern of {W3} fragments are preserved even in four-electron reduced clusters. The inter-triangular bonding is mainly due to the interactions of two tungsten atoms with the central C or N atom and is associated with the formation of a heteroatomic three-center bond.

Cluster compounds based on a new {Re

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 density of MgB 2 and hypothetical clusters {Mg 14 B 24 } was calculated and studied with quantum chemical methods based on the Density Functional Theory. Topological characteristics of electron density distribution are shown to be related to the anisotropy of local induced magnetic fields in {Mg 14 B 24 }. Our data correlate with experimental anisotropy of upper critical fields in MgB 2 in the vicinity of the phase transition into the superconducting state.

The electron precise [Mo3(μ3-Se)(μ-Se)3(dppe)3Br3]+ incomplete cuboidal complex, with six cluster skeletal electrons (CSE), was converted into the paramagnetic bicapped [Mo3(μ3-Se)2(μ-Se)3(dppe)3]+ cluster (1+), with an unusual seven metal electron population, by treatment with elemental Ga. The cluster core consists of an almost equilateral Mo3 triangle (Mo–Mo distances are in the range 2.7583(7)–2.7748(7) A with an average value of 2.77(3) A), capped by two selenide ligands. The remaining selenium atoms bridge adjacent metal atoms, defining a virtually planar Mo3(μ-Se)3 unit, with the capping Se atoms positioned above and below this plane. The new complex possesses a doublet ground state with the unpaired electron density delocalized over the three metal atoms. DFT calculations show that the HOMO has “a1” symmetry, precluding any Jahn–Teller distortion on the cluster core and giving support to EPR and structural observations.

Structural and magnetic properties in a number of Van Vleck and Curie–Weiss paramagnetics A3M2X9 compounds have been studied with DFT methods. The account of spin–orbit coupling is shown to provide a satisfactory agreement between experimental and calculated data on geometry and the type of magnetism for these compounds. The same level of theory predicts Van Vleck magnetism for all A3M2X9 compounds in the ground state, while thermal excitation increases interatomic metal–metal distances and changes the type of magnetism for M = Ti, V, Cr.

Monolayered titanium disulfide TiS2, a prospective nanoelectronic material, was previously shown to be subject to an exothermic solid-state D3h -D3d reaction that proceeds via a newly discovered transition state. Here, we study the reaction in detail using topological methods of quantum chemistry (quantum theory of atoms in molecules and electron localization function analysis) and show how electron density and chemical bonding between the atoms change in the course of the reaction. The reaction is shown to undergo a series of topological catastrophes, associated with elementary chemical events such as break and formation of bonds (including the unexpected formation of S-S bonding between sulfur layers), and rearrangement of electron density of outer valence and core shells.

The electronic structure and the metal–metal d 2 –d 2 interactions in dinuclear bioctahedral face-shared cluster complexes [M 2 X 9 ] 3− (M = V, Nb, Ta, and X = Cl, Br, I) have been studied with DFT and topological methods QTAIM and ELF. The ground states of the complexes are shown to be spin-paired and nonmagnetic only in the approximation of spin–orbit interaction. The result correlates well with experimental data on magnetic susceptibility for solid-state complexes containing [Nb 2 X 9 ] 3− and [Ta 2 X 9 ] 3− anions as well as for [V 2 X 9 ] 3− anions in low-temperature spin-paired modifications of Cs 3 V 2 Cl 9 and Rb 3 V 2 Br 9 complexes. The transition to the high-temperature spin-paramagnetic state of [V 2 X 9 ] 3− anions is shown to be related to the bifurcation of d 2 –d 2 interaction at some critical distance D CR (M–M) and to weakening of spin–orbit coupling in divanadium complexes.

For the first time the comparison of the theoretical and experimental data have shown that UV-vis absorption in the region of 600nm in colloidal solution of NbS

The review presents the progress in the analysis of low-temperature heat capacity of the metal-organic framework Zn2(C8H4O4)2.C6H12N2 (Zn-DMOF). In Zn-DMOF, left-twisted D3(S) and right-twisted D3(R) DABCO molecules (C6H12N2) can transform into each other by tunneling to form a racemate. Termination of tunneling leads to a phase transition in the subsystem of twisted molecules. It is suggested that Zn-DMOF may be considered a model system to study the mechanisms of phase transitions belonging to the same type as hypothetical Salam phase transitions.