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ПочтаSELECTED RESULTS OF COMPLETED RESEARCH STUDIES in 2012
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Selective two-step oxidation of μ2-S ligands to form cluster complex with unique μ2-coordination of SO3-ligand
Original method was suggested for two-step oxidation of cluster anion [Re12CS17(CN)6]6− by hydrogen peroxide in basic water solution to form cluster anions [Re12CS14(SO2)3(CN)6]6− and [Re12CS14(SO2)2(SO3)(CN)6]6−. A series of new compounds containing these anions was obtained. Cluster anion [Re12CS14(SO2)2(SO3)(CN)6]6− and compounds with it are the first example of rhenium clusters with μ2-SO3–ligand. This result shows unusual high stability of Re12 cluster anion and, particularly, terminal CN-ligands.
Selective two-step oxidation of μ2-S ligands to form cluster complex with unique μ2-coordination of SO3-ligand
«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−»Inorg. Chem. 2012. V. 51. P. 4359-4367.
High-efficiency minislab laser based on the KLu(WO4)2 : Tm(5%) crystal
In collaboration with Institute of Laser Physics, Siberian Branch of the Russian Academy of Sciences, the KLu(WO4)2 : Tm(5%) laser crystal growth process was developed by the modified Czochralski technique transfer method. The maximum CW laser output power (l = 1907 nm) upon the slab-shaped crystal of volume ~ 1 cubic millimeter, was as much as 10.66 W and the maximum slop efficiency was 43.0 %. Its orientation along <Nm> allows the maximum absorption of the pump, and opens the prospects for achieving higher powers of laser radiation output.
KLu(WO4)2 : Tm(5%) laser crystal grown by the modified Czochralski technique transfer method, and its laser characteristics
«High-efficiency 5%Tm:KLu(WO4)2 Nm-cut minislab laser»Laser. Phys. Lett. 2012. V. 9, N 11. P. 765-769.
New proton-conducting materials based on metal-organic frameworks
The extensive implementation of hydrogen-powered technology today is limited by a number of fundamental problems related to materials research. Fuel-cell hydrogen conversion technology requires proton-conducting materials with high conductivity at intermediate temperatures up to 120 °C. The development of such materials remains challenging because the proton transport of many promising candidates is based on extended microstructures of water molecules, which deteriorate at temperatures above the boiling point. Here we show the impregnation of the mesoporous metal–organic framework (MOF) MIL-101 by nonvolatile acids H2SO4 and H3PO4. Such a simple approach affords solid materials with potent proton-conducting properties at moderate temperatures, which is critically important for the proper function of on-board automobile fuel cells. The proton conductivities of the H2SO4@MIL-101 and H3PO4@MIL-101 at T = 150 °C and low humidity outperform those of any other MOF-based materials and could be compared with the best proton conductors, such as Nafion.
New proton-conducting materials based on porous coordination polymer MIL-101 and strong mineral acids
«Imparting High Proton Conductivity to a Metal-Organic Framework Material by Controlled Acid Impregnation»J. Am. Chem. Soc. 2012. V. 134. P. 15640-15643.
«CsHSO4 – Proton conduction in a crystalline metal-organic framework»Solid State Ionics. 2012. V. 225. P. 420-423.
Paramagnetic Lanthanides as NMR Probes of Chemical Exchange Processes and Temperature Sensors
An application of the 2D-EXSY of DNMR for investigation of the dynamic system [Ln(18-crown-6)(NO3)3] simplifies assignment and represents first experimental study of multi-site exchange. Two types of conformational dynamic processes were identified {∆G‡(210 K) = 28 ± 4, 39 ± 5, and 33 ± 4 kJ/mol (first type), ∆G‡(310 K) = 58 ± 6, 49 ± 6, and 45 ± 5 kJ/mol (second type), respectively for Ln = Ce, Pr and Nd}. Paramagnetic lanthanides represent NMR probes for the study of chemical exchange processes. In particular, as a result of paramagnetic chemical shifts in 4f complexes, the range of measurable rate constants expands considerably compared to the analogous range in diamagnetic compounds. Coordination compounds investigated in the paper are new type of thermometric NMR sensors and lanthanide paramagnetic probes for in situ temperature control in solution.
Paramagnetic Lanthanides as NMR Probes of Chemical Exchange Processes and Temperature Sensors
«Lanthanide Paramagnetic Probes for NMR Spectroscopic Studies of Fast Molecular Conformational Dynamics and Temperature Control. Effective Six-Site Proton Exchange in 18-Crown-6 by Exchange Spectroscopy»Inorg. Chem. 2012. V. 51. N 3. P. 1427-1433.
2D-semiconductor → 1D-metal transition in monolayers of molybdenum dichalcogenides МоХ2
The semiconductor-metal transition in molybdenum dichalcogenide is first shown with the methods of quantum chemistry to be accompanied with the rearrangement of electron density corresponding to the 4dz2 orbital of molybdenum. The two-dimensional trigonal structure of the semiconductor is marked by multicenter interactions between molybdenum atoms. When passing from semiconductor to metal the interactions change to form one-dimensional zigzag chains. The obtained result clarifies the specific electronic mechanism of the semiconductor-metal transition. Together with grapheme, dichalcogenides of molybdenum and other transition metals are considered as new and perspective materials to use in transistors, current reversers, photodetectors and electroluminescent devices in nanotechnologies.
Topological changes in electron density of HOMO Mo(4dz2) orbitals at “semiconductor-metal” transition
«Transition from 2-D Semiconductor to 1-D Metal State and Electron Density Distribution in Nanolayered MoX2 (X = S, Se, Te)»J. Phys. Chem. C. 2012. V. 116 . N 38. P. 20651-20655.
Rare earth metal polysulfides: from the equilibrium p-T-x diagram to 24-fold superstructure of ZrSiS type
Methodology was developed for accurate refinement of the complex structure of the layered REM polysulfides with the sulfur deficit up to composition LnS2-x (x<0.15), and attention focuses on structural peculiarity of the defective planar layer of sulfur. For three REM polysulfides (Tb, Dy, Ho), the structure was found to be like the commensurate 24-fold superstructure where the anionic sulfur layer is composed from dimmers S2, the single ions S2– surrounded by dimmers, and vacancies. High quality single crystals of the polysulfides were grown that provided precise structural description of the sulfur layer with the complicate arrangement. High reliability of the structure refinement is supported by agreement of the structure data with composition and experimental density measured by independent techniques. The local structural heterogeneity of the polysulfides is realized by a set of interesting physical properties, for example, the formation of commensurate charge density waves (CDW”s) and the lattice instability predisposed toward phase transitions.
Structure and properties of rare earth metal polysulfides with the sulfur deficit like LnS2-x (x<0.15)
«Structural Frustration and Occupational Disorder: the Rare Earth Metal Polysulfides Tb8S14.8; Dy8S14.9, Ho8S14.9 and Y8S14.8»Inorg. Chem. 2012. V. 51. P. 282-289.
Spin-crossover in the complex of iron(II) nitrate with tris(3,5-dimethylpyrazol-1-yl)methane
Single crystal of [Fe(L)2](NO3)2 (where L = (3,5-dimethyl)pyrazolylmethane) survives the phase transition resulted from the thermo-induced 1A1 ↔ 5T2 spin crossover. For the first time both high- and low-spin state of the complex are structurally characterized. Results are in good agreement with the data of magnetic measurements.
Spin-crossover in the complex of iron(II) nitrate with tris(3,5-dimethylpyrazol-1-yl)methane
«Spin-crossover in the complex of iron(II) nitrate with tris(3,5-dimethylpyrazol-1-yl)methane»Inorg. Chim. Acta. 2012. V. 382. Р. 1-5.
New rhodium polytungstate: a catalyst for electrooxidation of water
A new polytungstate with a unique tetrarhodium core has been prepared. Reaction of the tungstate with Rh(II) acetate leads to the formation of new rhodium polytungstate where two {W9} units sandwich a unique oxo-bridged tetrarhodium {Rh4} core. During the reaction Rh(II) oxidizes into Rh(III) which condences into the tetranuclear unit assisted by the polytungstate as template. X-ray structural analysis and 183W NMR show that the structure of the rhodium polytungstate is identical both in solid and in solution. The electrochemical studies show that this complex is an active catalysts of electrochemical water oxidation, which starts already at +1.1 V (vs. Ag/AgCl). The catalytic cycle possibly involves intermediate oxidation of Rh(III) into Rh(IV), followed by water oxidation.
Synthesis and structure of the polytungstate with a new tetrarhodium core
«Self-assembly of polyoxotungstate with tetrarhodium-oxo core: synthesis, structure and 183W NMR studies»Chem. Commun. 2012. V. 48. N 53. P. 6666-6668.
Modification and dispersion of hexagonal boron nitride – inorganic analogue of graphene
Functionalization of bulk hexagonal boron nitride (h-BN) is realized through reaction with 30% hydrogen peroxide in an autoclave at 1000C. The modified product forms stable colloid solutions in water (0.26–0.32 g·L−1) and N,N-dimethylformamide (0.34–0.52 g·L−1) upon mild ultrasonication. The yield of “soluble” h-BN reaches about 70 wt%. The dispersions contain few-layered h-BN nanosheets with lateral dimensions in the order of several hundred nanometers. Such dispersions may be used for preparation of thin dielectric films through vacuum filtration or spray method for more complex coatings.
Scheme for preparation of dispersible functionalizaed h-BN nanosheets
«Functionalization and Dispersion of Hexagonal Boron Nitride (h-BN) Nanosheets Treated with Inorganic Reagents»Chem.-Asian J. 2012. V. 7. N 3. P. 554-560.
Nanoporous Au-Pd alloy for electrocatalysis
It is developed preparation approach for 3D nanoporous alloys Au0.67Pd0.33 which is realized in a one-pot reaction under thermal decomposition of single-source precursor [Pd(NH3)4][AuCl4]2. In situ real-time synchrotron X-ray diffraction was used to study the formation mechanism for Au-Pd nanoalloy. Hydrogen oxidation catalytic reaction (HOR) over the new material was studied using rotating disk electrode at low temperature in pure H2 and in the presence of 1100 ppm of CO. The catalysts demonstrate exhibits substantially enhanced catalytic performance in the HOR both in the absence and in the presence of CO.
Synthesis of nanoporous Au0.67Pd0.33 alloy and its electrocatalytic properties
«In situ synchrotron study of Au–Pd nanoporous alloy formation by single-source precursor thermolysis»Nanotechnology. 2012. V. 23. P. 405302-405311.
High-spin Rhenium Cluster with Nido-cubane Core
Interaction of Re3S7Br7 with 1,2-bis(diphenylphosphino)ethane (dppe) gives the paramagnetic cluster [Re3S4(dppe)3Br3]Br with nido-cubane core. Magnetic susceptibility data and DFT calculations show that the parallel orientation of the spins of three unpaired electrons results in the quartet ground state with total spin of 3/2. High spin state of the novel cluster makes its derivatives attractive building blocks for the design of the heterospin coordination polymers.
![High-spin cluster [Re3S4(dppe)3Br3]Br](/img/en/science/results/2012/small/../big/results2012_10.png)
High-spin cluster [Re3S4(dppe)3Br3]Br
«Synthesis, molecular and electronic structure of an incomplete cuboidal Re3S4 cluster with an unusual quadruplet ground state»Chem. Commun. 2012. V. 48. P. 2713-2715.
