N. K. Moroz

High Proton Conductivity and Spectroscopic Investigations of Metal–Organic Framework Materials Impregnated by Strong Acids

Strong toluenesulfonic and triflic acids were incorporated into a MIL-101 chromium(III) terephthalate coordination framework, producing hybrid proton-conducting solid electrolytes. These acid@MIL hybrid materials possess stable crystalline structures that do not deteriorate during multiple measurements or prolonged heating. Particularly, the triflic-containing compound demonstrates the highest 0.08 S cm(-1) proton conductivity at 15% relative humidity and a temperature of 60 °C, exceeding any of todays commercial materials for proton-exchange membranes. The structure of the proton-conducting media, as well as the long-range proton-transfer mechanics, was unveiled, in a certain respect, by Fourier transform infrared and (1)H NMR spectroscopy investigations. The acidic media presumably constitutes large separated droplets, coexisting in the MIL nanocages. One component of proton transfer appears to be related to the facile relay (Grotthuss) mechanism through extensive hydrogen-bonding interactions within such droplets. The second component occurs during continuous reorganization of the droplets, thus ensuring long-range proton transfer along the porous structure of the material.

Cyclic tungstoselenites based on {Se2W12} units.

The reaction of Na2WO4 and SeO2 under moderately acidic conditions yielded a novel 39-tungsto-6-selenite, [(Se2W12O46(WO(H2O))3](24-) (1), isolated as Na24[H6Se6W39O144]·74H2O. The macrocyclic polyanion consists of three {Se2W12} fragments connected via three trans-{WO(H2O)}(4+) groups. The same {Se2W12} building block is present in the structure of [(Se2W12O46)2{Mn2Cl(H2O)2}{Mn(H2O)2}2(SeO)2](13-) (2), which was obtained from the same reagents in the presence of MnCl2. The compounds were characterized by single-crystal X-ray diffraction, (77)Se NMR, Fourier transform infrared, and Raman spectroscopy.

Unusual H-bonding in novel cyano-cluster polymeric hydrates [(H){Ln(H2O)4}{Re6S8(CN)6}]·2H2O (Ln = Yb, Lu)

X-Ray studies and (1)H NMR measurements for novel cyano-bridged polymers [(H){Ln(H(2)O)(4)}{Re(6)S(8)(CN)(6)}]*2H(2)O (Ln = Yb, Lu) reveal temperature dependence of proton localization: acid protons are trapped between nitrogen atoms at low temperatures, but can be transferred to the water sublattice at higher temperatures; this transfer resulted in intermolecular proton exchange.

Cd2+ complexation with P(CH2OH)3, OP(CH2OH)3, and (HOCH2)2PO2(-): coordination in solution and coordination polymers.

The coordination of Cd(2+) with P(CH(2)OH)(3) (THP) in methanol was followed by (31)P and (111)Cd NMR techniques. A cadmium-to-phosphine coordination ratio of 1:3 has been established, and effective kinetic parameters have been calculated. Air oxidation of THP in the presence of CdCl(2) at room temperature produces coordination polymer (3)(∞)[Cd(3)Cl(6)(OP(CH(2)OH)(3))(2)] (1). The same oxidation reaction at 70 °C gives another coordination polymer, (∞)[CdCl(2)(OP(CH(2)OH)(3))] (2). Complexes 1 and 2 are the first structurally characterized complexes featuring OP(CH(2)OH)(3) as a ligand that acts as a linker between Cd atoms. The addition of NaBPh(4) to the reaction mixture gives coordination polymer (∞)[Na(2)CdCl(2)(O(2)P(CH(2)OH)(2))(2)(H(2)O)(3)] (3) with (HOCH(2))(2)PO(2)(-) as the ligand. Coordination polymers 1-3 have been characterized by X-ray analysis, elemental analysis, and IR spectroscopy.

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.

Synthesis and Characterization of [(OH)TeNb5O18]6– in Water Solution, Comparison with [Nb6O19]8–

Reaction of [Nb6O19](8-) with H6TeO6 in water gives telluropentaniobate [(OH)TeNb5O18](6-) (1) as single product, which was isolated as Na(+) and mixed Na(+)/K(+) salts. Crystal structures were determined for Na6[(OH)TeNb5O18]·15H2O (Na6-1) and K6Na[Nb(5.5){Te(OH)}(0.5)O(18.5)]·26H2O (K6Na-1). Formation of 1 was monitored with electrospray ionization mass spectrometry (ESI-MS) and (125)Te NMR techniques. Capillary electrophoresis was used to calculate electrophoretic mobilities and radii of the anionic species in solutions of [(OH)TeNb5O18](6-) and [Nb6O19](8-) in borate buffer. No condensation or degradation products were detected. Reactions of 1 with {Cp*Rh}(2+) sources gives 1:1 and 2:1 hybrid polyoxometalate, which are present in solution as a mixture of isomers, as detected by (125)Te NMR. The isomerism is related to various possibilities of coordination of {Cp*Rh}(2+) to different {M3O3} faces, relative to the unique Te atom. According to ESI-MS experiments in water and methanol, rapid redistribution of the organometallic fragments between the 1:1 and 2:1 complexes takes place. The 1:1 complexes are more stable in water, while 2:1 complexes dominate in methanol. X-ray structural analysis of the crystals isolated from 2:1 reaction mixture allowed identification of Na3[{Cp*Rh}2TeNb5O19]·24H2O (Cp*2Rh2-1) with two {Cp*Rh}(2+) fragments capping the opposing faces of the Lindqvist anion.

Synthesis, structure and NMR studies of trinuclear Mo3S4 clusters coordinated with dithiophosphate and chiral carboxylate ligands

New chiral cluster complexes containing (S)-mandelate and (S)-phenyllactate ligands, [Mo3S4(dtp)3(μ-(S)-mandelate)(py)] (1) and [Mo3S4(dtp)3(μ-(S)-phenyllactate)(py)], were prepared from [Mo3S4(dtp)3(μ-dtp)(H2O)] (dtp = (EtO)2PS2) by ligand substitution. The crystal structures of 1 and 2 were determined by X-ray diffraction. Detailed variable-temperature 31P{1H} and 1H NMR studies of solutions of 1 and 2 in non-coordinating solvents (CDCl3, CD2Cl2) demonstrated three dynamic processes at the Mo–Py coordination site: diastereomer interconversion [(PS) to (MS)] which is inhibited at low temperatures; pyridine rotation around the Mo–py bond (180°-flip), and pyridine exchange in the presence of added pyridine. Activation parameters for all exchange processes have been estimated.

Arrangement and Diffusive Mobility of Extraframework Species in the Hydrated Ammonium Forms of Zeolites Clinoptilolite and Chabazite

The location and diffusive mobility of ammonium ions and water molecules in the channels of the NH4‐substituted forms of the natural zeolites clinoptilolite (NH4)6.5[Al6.5Si29.5O72] · 12.6H2O and chabazite (NH4)9.6Ca0.6Na0.3[Al11.1Si24.9O72] · 25.8H2O were studied by X‐ray diffraction analysis and 1H NMR spectroscopy. The arrangement of the extraframework subsystem was shown to be largely determined by hydrogen bonds N—H...O(H2O) of length 2.7–2.9 Å. The diffusive mobility of the ions was found to correspond to abnormally low energy barriers, similar to those for H2O diffusion. The activation parameters for the diffusion jumps of the ions and molecules are E(NH4) = E(H2O) = 31(2) kJ/mole, ν0(NH4) = 2 · 1011 sec-1, ν0(H2O) = 4 · 1012 sec-1 in NH4‐chabazite and E(NH4) = E(H2O) = 25(1) kJ/mole, ν0(NH4) = 2 · 1010 sec-1, ν0(H2O) = 3 · 1011 sec-1 in NH4‐clinoptilolite. It is suggested that the development of ion and molecular diffusion is caused by the same defects, whose formation with temperature rise is controlled by H‐bond rearrangement.

The system of hydrogen bonds in Ba2Re6Te8(CN)6·12H2O: Simulation and NMR study

The crystal hydrate Ba2Re6Te8(CN)6· 12H2O whose structural fragments are the cluster onions [Ba2Re6Te8(CN)6]4− is studied by1H NMR. In the triclinic cell (space group P-1), the barium atoms coordinated by six water molecules are united into the dimers [Ba· 5H2O]24+ by two bridging H2O molecules; the water molecules lying outside the coordination sphere of Ba are located in the structure channels running along the [001] direction. Diffusion of H2O molecules was found in the range of temperatures 100‡C below the temperature of intense dehydration of the crystal. The structure of the water lattice of the compound is modeled by calculating Coulomb interactions between hydrogen and surrounding atoms and analyzing the NMR spectra recorded under translational diffusion conditions for H2O. Half of the protons in H2O molecules are involved in the formation of hydrogen bonds whose lengths lie within 2.78–2.86 å (O-H…O) and 2.92-3.13 å (O-H…N). The water lattice structure is preserved up to ≈100‡C. The water subsystem is radically rearranged upon subsequent heating followed by partial dehydration of the crystal.

Ionic exchange in clinoptilolite and localization of H2O molecules by1H NMR

The Li-, Na-, K-, Cs-, Ca-, Ba-, and NH4-forms of natural clinoptilolite from the White Stratum deposit, Bulgaria, have been obtained by ionic exchange in solutions. The1H NMR spectr of the samples have been recorded at room temperature and the dipole-dipole coupling constants of zeolite water protons have been measured. The characteristics of regular redistribution of water molecules in structural positions of clinoptilolite upon substitution of exchange Na and Ca cations by the larger K and Ba cations have been established.