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Heterometallic coordination compounds based on copper(II) and palladium(II) β-diketonates $$\text{ }\!\![\!\!\text{ Cu}{{\text{L}}_{\text{2}}}\cdot \,\text{Pd}{{\text{L}}_{\text{2}}}]$$ (L = 2-methoxy-2,6,6-trimethylheptane-3,5-dionato) and $$\text{ }\!\![\!\!\text{ Cu}{{(\text{hfa})}_{\text{2}}}\,\cdot \text{Pd}{{\text{L'}}_{\text{2}}}]$$ (hfa = hexafluoroacetylacetonate, L′ = 1,1,1-trifluoro-5-methoxy-5-methylhexane-2,4-dionato) with a polymeric chain-like crystal structure can be used to prepare Cu–Pd films by MOCVD. It was previously suggested that the Pd:Cu ratio in the films is related to the stability of binuclear complexes $$\text{Cu}{{\text{L}}_{\text{2}}}\cdot \,\text{Pd}{{\text{L}}_{\text{2}}}$$ and $$\text{Cu}{{(\text{hfa})}_{\text{2}}}\,\cdot \,\text{Pd}{{\text{L'}}_{\text{2}}}$$ (the forms these compound adopt in the gas phase). In the present work, the most probable structure of such binuclear complexes at 0 K is determined, their stability is studied, and interatomic interactions are analyzed by density functional theory calculations. The monometallic fragments of the complexes are connected by a network of weak non-covalent interactions, the Cu⋯O contact being the strongest one. When modeling such systems, empirical corrections are shown to be essential for the account of dispersion interactions.

An organic ligand 1-(1H-benzimidazol-1-ylmethyl)-1H-benzotriazole (bta) and two zinc complexes of the composition [Zn(bta)2Hal2] (Hal = Cl, Br) were synthesized. The crystal structure of the complex [Zn(bta)2Cl2] was determined and its features were discussed. According to X-ray diffraction data, the central atom has a tetrahedral environment composed of two nitrogen atoms from two ligand molecules coordinated in monodentate mode and two terminal chloride ions. Density functional theory (DFT) calculations of the ligand and complex [Zn(bta)2Cl2] were carried out. A study of the luminescence properties of the compounds synthesized suggests that excitation of the zinc complexes gives rise to a dual-band luminescence similar to that of the free ligand. Most probably, the emission originates from π—π* and π—π* intra-ligand transitions.

Temperature dependence of molar heat capacity of Ni2(bdc)2(dabco) was first measured by the method of vacuum adiabatic calorimetry in the temperature region of 5–295 K. A heat capacity anomaly was discovered above 60 K. The analysis of the electronic structure of a dimeric complex Ni2(O2C-)4 testifies that the observed anomaly is the Schottky anomaly caused by thermal excitation of d electrons of Ni2+(3d8) ions. The experimental heat capacity values in the vicinity of the maximum of the Schottky anomaly exceed its calculated values by ∼10%. This fact is explained by the spin–lattice interaction between d electrons of Ni2+ ions and lattice vibrations of Ni-DMOF (Ni2(bdc)2(dabco)). The obtained experimental Cp values were used to calculate standard thermodynamic functions (heat capacity, enthalpy, and entropy) of the studied compound.

A reaction between ReI3 and KCN at elevated temperature led to the formation of the new cyanometalate cluster anion [{Re4(μ3-CCN)4}(CN)12]8– (1). The anion contains μ3-CCN3– ligands, which are stab...

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.

Today, the synthesis of biocompatible and bioresorbable composite materials such as “polymer matrix-mineral constituent,” which stimulate the natural growth of living tissues and the restoration of damaged parts of the body, is one of the challenging problems in regenerative medicine. In this study, composite films of bioresorbable polymers of polyvinylpyrrolidone (PVP) and sodium alginate (SA) with hydroxyapatite (HA) were obtained. HA was introduced by two different methods. In one of them, it was synthesized in situ in a solution of polymer mixture, and in another one, it was added ex situ. Phase composition, microstructure, swelling properties and biocompatibility of films were investigated. The crosslinked composite PVP-SA-HA films exhibit hydrogel swelling characteristics, increasing three times in mass after immersion in a saline solution. It was found that composite PVP-SA-HA hydrogel films containing HA synthesized in situ exhibited acute cytotoxicity, associated with the presence of HA synthesis reaction byproducts—ammonia and ammonium nitrate. On the other hand, the films with HA added ex situ promoted the viability of dental pulp stem cells compared to the films containing only a polymer PVP-SA blend. The developed composite hydrogel films are recommended for such applications, such as membranes in osteoplastic surgery and wound dressing.

DFT calculations within the two-component quasirelativistic approach and further analysis of 103Rh NMR shielding (including the natural bond orbitals method) in a series of flat-square complex anions cis-[X1X2Rh(CO)2]− (X1, X2 = Cl, Br, I) are used to determine the role of relativistic spin-orbit effects in 103Rh NMR shielding in these systems. Electron delocalization observed in these complexes provides the possibility of relativistic spin-orbit effects but complicates the interpretation of 103Rh NMR shielding in terms of chemically meaningful fragments of electronic system (lone pairs, chemical bonds).

Local atomic and electronic structure of Dy- and Yb-based dibenzoylmethanide complexes has been investigated by analysis of experimental and theoretical L3-edge XANES spectra. The local atomic structure similarity between recrystallized and as-synthesized samples has been proved by XANES. Differences in the experimental XANES spectra collected for a Ln-complexes with a different ligand ratio (dbm-): (O-btd-) have been observed and assigned with a higher abundancy of elongated Ln-N bonds with respect to Ln-O for the sample where Ln-ions coordinated by higher number of O-btd- ligands. In this work we also critically discussed XANES simulations based on monoelectronic approach as implemented in FDMNES code for L3-edge spectra calculated for Ln-complexes. Density of electronic state calculation has been performed in order to elucidate the origin of the XANES features. Since the product yield of as-synthesized Ln-complexes is significantly higher rather than after re-crystallization this work demonstrate a high potential of DFT-assisted XANES analysis for the structural investigation of as-synthesized complexes without long-range atomic ordering.

New tetrahedral anionic rhenium cluster complexes [{Re4(PO)3(PO2)}(CN)12]8- (1) and [{Re4As2(AsO)2}(CN)12]8- (2) have been synthesized by the reaction of ReI3 with NaCN and Pred or KCN and Asgray, respectively. Compound 2 was further oxidized by aqueous H2O2 to produce the cluster anion [{Re4(AsO)4}(CN)12]8- (3). The anions contain new pnictogen/oxygen-based ligands, PO23- and AsO3-, which were stabilized by the coordination to the triangular faces of the tetrahedral Re4 metallocluster in μ3-mode. All three compounds were crystallized as either sodium or potassium salts, and their crystal structures were determined by single crystal X-ray diffraction analysis.

The first titanium selenoiodide Ti4Se9I6 was synthesized as black crystals by heating of Ti, Se, and I2 at 250 °C in 5:9:5 M ratio. The crystal structure of the compound was solved by X-ray single-crystal diffractometry (sp. gr. P-1, a = 7.9652(10), b = 10.3390(15), c = 15.692(2) A; α = 79.116(7)°, β = 75.861(7)°, γ = 71.437(7)°; Z = 2) with final R1 = 0.0397. The structure includes square {Ti4(μ4-Se)(μ2-Se2)4} fragment coordinated by four terminal and four bridging μ2-I atoms. Ti4+ has d0 configuration, and stability of the structure fragments is provided by metal to ligand bonding which was confirmed by DFT calculations.

—Quantum-chemical calculations show a tendency of SiO2 molecule to transform from linear to isomeric cyclic (bent) form and back. In the latter case, the energy released during the transition isomeric SiO2 → linear SiO2 is about 240 kJ/mole. This hypothetic structural transition of submolecular SiO2 fragments in mantle minerals is supposed to initiate deep-focus high-energy earthquakes at the upper–lower mantle boundary. It is at this depth (600–670 km) that the subducting oceanic slab is delaminated: Its upper part moves “horizontally” along the upper–lower mantle boundary, while its lower part separated into blocks subsides into the lower mantle and reaches the Dʺ layer to accumulate there.

New molecular niobium(IV) complexes NbCl4(OPPh3)2(1) and NbBr4(OPPh3)2(2) are synthesized by heating respective niobium pentahalide with a mixture of triphenylphosphine and triphenylphosphine oxide. For the obtained compounds the crystal structure is solved: 1P-1, a = 13.3540(5) A, b = 9.4461(3) A, c = 9.5635(3) A, α = 93.084(1)°, β = 121.263(1)°, γ = 115.058(1)°, Z = 1, R1 = 0.0194; 2P-1, a = 13.308(2) A, b = 9.5934(8) A, c = 9.5556(9) A, α = 93.975(3),°, β = 119.391(4)°, γ = 114.740(4)°, Z = 1, R1 = 0.0184. The unpaired electron is mainly located on the niobium atom, which is supported by quantum chemical calculations and EPR spectroscopic results.

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.

A reaction between ReI

The optical properties of metal-organic frameworks [M

The molar heat capacity of Zn2(C8H4O4)2.C6H12N2 (Zn-DMOF) was measured for the first time at 4.8–302 K in atmospheres of noble gases 3He, 4He, and 40Ar under pressures P up to 1.52·105 Pa. It is shown that phase transitions reported earlier at Tc = 13, 58.9, and 131.2 K are second-order phase transitions associated with the ordering/disordering of organic ligands in Zn-DMOF. The transition entropy (ΔSm) in the temperature range of phase transitions associated with the ordering/disordering of C6H12N2 molecules decreases at Tc = 13 K and increases at Tc = 58.9 K as P increases from 0.51·105 to 1.52·105 Pa. The values of ΔSm do not depend on P in the region of the phase transition at Tc = 131.2 K associated with the ordering/disordering of C8H4O42− anions.

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.

In the present study, the heat capacities of barium cerate doped by gadolinium and yttrium oxides were measured for the first time in the temperature range of 166–790 K. The differential scanning calorimeter was used for investigation. There was reproducible anomaly with maximum at 601 K and minimum at 679 K. The experimental results were used to calculate the thermodynamic functions: smoothed heat capacities, enthalpy increment (H m o (T) − H m o (298.15)), and entropy (S m o (T)). The heat capacity in the temperature range of 166–602 K was described by a polynomial of the form: C p,m o (T) = 83.140 + 0.14943 T − 1.1537 × 10−4 T2 − 3.6358 × 105/T2 (J mol−1 K−1). Heat capacity of BaCe0.8Y0.1Gd0.1O2.9 in the temperature range of 602–680 K was described by a polynomial: C p,m o (T) = − 118.18 + 0.71961 T − 5.5387 × 10−4 T2 + 5.6948 × 10+6/T2 (J mol−1 K−1). The heat capacity in the temperature range of 680–790 K was well described by the equation: C p,m o (T) = 1987.1 − 6.9263 T + 8.3407 × 10−3 T2 − 3.1992 × 10−6 T3 (J mol−1 K−1).

Triethylamine (Et3N) aqueous solutions with different weight contents of dissolved molecules (9, 18, 25, 30, and 42 wt% of Et3N) were studied for the first time by the 1H NMR method in the region of the liquid–liquid phase transition. After an interface between two phases was formed, anomalous inhomogeneous broadening of 1H NMR lines of Et3N molecules was discovered in the Et3N rich phase. The inhomogeneous character of broadening depends on the weight content of dissolved molecules and is observed up to 313 K. It is concluded that the studied systems exist in the transition region between critical and classical states.

Tungsten trioxide has been found to be a convenient precursor for the synthesis of metal cluster compounds with new types of cluster cores. The reaction between WO3 and KCN led to the formation of the cluster complex [{W6(μ4-O)2(μ3-CCN)4}(CN)16]10−. Unexpectedly, it includes the fully deprotonated form of acetonitrile, the CCN3− anion, as a μ3-bridging ligand coordinated to the trigonal faces of the bitetrahedral W6 metallocluster. A similar complex [{W6(μ4-O)2(μ3-As)4}(CN)16]10− containing μ3-As3− ligands instead of μ3-CCN3− ones has been synthesized by the reaction between WO3, As and KCN.

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.

It was previously suggested that a metal-organic framework [Zn 2 (C 8 H 4 O 4 ) 2 ·C 6 H 12 N 2 ] could be a possible candidate for observation of parity violation effects related to tunneling of C 6 H 12 N 2 (DABCO) fragment between chiral twisted states. We have performed relativistic four-component and two-component calculations of parity violating energy (PVE) term for twisted isomers of isolated DABCO molecule and [Zn 2 DABCO] 4+ cation. We also discuss the nature of PVE in these systems with the help of analysis of individual atomic contributions to PVE and visualization of electron chirality density.

Selective substitution of μ-SO22- groups by either O2- or Se2- ions occurs upon heating the bioctahedral rhenium cluster complex K6[Re12CS14(μ-SO2)3(CN)6] in air atmosphere or in the presence of a Se source, respectively, manifesting the remarkable lability of SO22- ligands bound to a transition-metal cluster. A series of compounds based on the new mixed-ligand anions, [Re12CS14(μ-O)3(CN)6]6-, [Re12CS14(μ-Se)3(CN)6]6-, and [Re12CS14(μ-O)3(OH)6]6-, were isolated and their solid-state structures were elucidated by single-crystal X-ray diffraction analysis. Along with the previously reported μ-sulfide clusters, the new species constitute a series of rhenium anionic complexes with the common formula [Re12CS14(μ-Q)3L6]6- (Q = O, S, Se, L = CN-; Q = O, S, L = OH-), within which the total charge and number of cluster valence electrons (CVEs) are constant. The article presents insights into the mechanistic and synthetic aspects of the substitution process, and it comprehensively discusses the influence of inner ligand environment on the structure, spectroscopic characteristics, and electrochemical behavior of the novel compounds.

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.

The 1H NMR spectra in a binary aqueous triethylamine solution are recorded with a lower critical point of the liquid–liquid phase transition. It is found that, above the critical temperature the 1H NMR spectra of water and triethylamine molecules in the phase with a predominant content of triethylamine molecules are characterized by an inhomogeneous broadening. It can be supposed that the found broadening is due to the features of the molecular distribution at the interface.

1H NMR spectra were recorded in triethylamine (D2O/triethylamine) binary aqueous solution which had a lower critical point of the liquid–liquid phase transition. The spectra in the phase with predominant content of triethylamine molecules were found to get broaden inhomogeneously above the critical temperature. It is hypothesized that D2O/triethylamine system at 10−3 ≤ (T–Tc)/Tc ≤ 10−1 falls into the area of long-wave fluctuations of the order parameter. The revealed broadening can be attributed to the intermolecular interaction between triethylamine and water in the vicinity of the two-phase boundary.

The mobility of aromatic chiral molecules 1-phenylethanol and 1-phenyl-1-propanol in liquids was studied by 1H NMR spectroscopy depending on the strength of the external magnetic field, temperature, and concentration ratio of enantiomers. The data obtained were analyzed using Arrhenius law. The activation parameters were found to depend on the applied field. This effect is caused by the induced magnetic moments in aromatic molecules. The use of strong magnetic fields seems to be promising for investigation of intermolecular interactions of chiral molecules.

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.

Four new tetranuclear complexes, [Ln4(dbm)4(O-btd)6(OH)2] 1a (Ln = Yb), 1b (Ln = Dy) and [Ln4(dbm)6(O-btd)4(OH)2] 2a (Ln = Yb), 2b (Ln = Dy) (O-btd = 4-hydroxo-2,1,3-benzothiadiazolate and dbm = dibenzoylmethanide), and their solvates with toluene and tetrahydrofuran were synthesized. The magnetic properties of the complexes 1a, 1b, 2a and 2b have been studied, revealing different magnetic susceptibility patterns for the Yb(III) and Dy(III) complexes in the temperature range 80–300 K. Upon lowering the temperature, a weak antiferromagnetic ordering is observed for both Yb compounds, while the Dy derivatives are assumed to show weak ferromagnetic interactions. The Yb complexes 1a and 2a demonstrate strong NIR luminescence at ∼1000 nm in CH2Cl2 solution upon excitation of the (O-btd)− ligand. This observation suggests the (O-btd)− ligand to be an efficient antenna ligand for lanthanide-based NIR luminescence.

Differential scanning calorimetry and nuclear magnetic resonance were used to investigate thermal effects in the guest-host systems where homochiral metal-organic sorbent [Zn2 (bdc)(S-lac)(dmf)] is considered as a host while 1-phenylethanol enantiomers and their racemic mixture serve as guest molecules. A maximum energy gain from the guest-host interaction was observed in the system with the racemic mixture. The effect of host-guest recognition was revealed for the case of the host and guest having a similar type of chirality in the presence of antipode guest molecules.

The work interprets experimental data for the heat capacity of Zn2(BDC)2(DABCO) in the region of second-order phase transitions. The proposed understanding of the processes occurring during phase transitions may be helpful to reveal quantum Zeno effects in metal-organic frameworks (MOFs) with evolving (unstable) structural subsystems and to establish relations between quantum measurements and the entropy of phase transitions., Comment: 7 pages, 1 figure, 1 table

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.

New tetrahedral anionic rhenium cluster complexes [{Re

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 magnetic properties of metal-organic framework compounds [M2(C8H4O4)2 · C6H12N2] (M = Cu, Ni, Co) were studied in the region of 300–4 K by magnetic susceptibility and 1H magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The interaction between the magnetic ions M was found to be antiferromagnetic at the temperatures above 100–150 K. Lowering the temperature changes the interaction character to ferromagnetic. The exchange interaction was found between 1,4-diazabicyclo[2,2,2]octane (dabco) molecules and magnetic ion. Magnetic properties in metal-organic framework compound.

The temperature dependence of the heat capacity at second-order phase transitions that were previously detected in the [Zn2(C8H4O4)2 · C6H12N2] metal-organic framework compound has been analyzed. The critical exponents have been obtained. It has been shown that the behavior of the heat capacity below the critical temperature of 60 K, which is attributed to the violation of the mirror symmetry of C2H12N6 molecules, is exponential.

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.