Hydrothermal synthesis and crystal structure of sandwich-like heteropolymolybdophosphates

Sandwich-like heteropoly molybdochromophosphates of supermolecular compound [NH3(CH2)(6)NH3](2)H-3{Cr[Mo6O15(HPO4)(H2PO4)(3)](2)}. 4H(2)O has been hydrothermally synthesized and the single crystal structure has been determined by X-ray diffraction. The crystal data are has follows: triclinic, space group P (1) over bar a=12.156(2), b=12.809(3), c=13.530(3) Angstrom, alpha=102.46(3)degrees, beta=93.67(3)degrees, gamma=93.46(3)degrees, V=2046.9(7) Angstrom(3), Z=1, M-r=2768.69, D-c=2.246 g/cm(-3), F(000)=1337, mu=2.162 mm(-1). The structure has been refined to R=0.0666 and wR=0.1745 by full-matrix least-squares method. The title compound is composed of 1, 6-diaminohexane, water molecules, and {Cr[Mo6O15(HPO4)(H2PO4)(3)](2)}(7-) anion which consists of six oxygen atoms from two [Mo6P4] units with a sandwich-like transition metal atom Cr located at the center of symmetry.

Synthesis and characterization of sandwiched heteropolycompound

New complex K5O4Na4H5 [Sn-3(PW9O34)(2)]. 16N(2)O was prepared and its structure was determined by elemental analysis, IR, P-31, W-183 NMR, polarography, XPS and X-ray crystallography. The anion has A-alpha-Keggin structure. The new complex crystallize is the monoclinic, P2(1)/n with a = 1.3625 (3) nm, b = 2.3625 (5) nm, c = 2.9306 (6) nm, alpha = 90 degrees, beta = 99.67 (3)degrees, gamma = 90 degrees, V = 9.299 nm(3), Z = 4.

Interactions of thiamine with anions: (Hthiamine)(thiamine) heptaiododimercurate dihydrate and its dimethanol monohydrate

In the title compounds, 3-[(4-amino-2-methyl-5-pyrimidinio)methyl] -5-(2-hydroxyethyl)-4-methylthiazolium(2+) 3-[(4-amino-2-mcthyl-5-pyrimidinyl)methyl]-5-(2-hydroxyethyl)-4-methylthiazolium( 1+) heptaiododimercurate dihydrate, (C12H18N4OS)(C12H17N4OS)[Hg2I7]. 2H(2)O, (I), and its dimethanol monohydrate, (C12H18N4OS)(C12H17N4OS)[Hg2I7]. 2CH(3)OH . H2O (2), a crystallographic centre of symmetry in (1) or a twofold axis in (2) is imposed between the protonated and deprotonated thiamine molecules, resulting in a statistically half-occupied proton attached at N1' of the pyrimidine ring. The Hg2I73- anion, residing on the centre of symmetry in (1) or on the twofold axis in (2), interacts with two thiamine molecules, each through a C2-H ... I ... pyrimidine-ring interaction. This bridging interaction is a characteristic of thiamine in the F conformation.

Fabrication and characterization of heteropolyanion Langmuir-Blodgett films

The possibility of the formation of Langmuir-Blodgett (LB) films with dimethyldioctadecylammonium (DODA) after the addition of cobalt(II)-substituted Dawson-type tungstodiphosphate anion (briefed as (H2O)(CoP2W17O618-)-P-11) in the subphase has been explored. Marked modifications of the compression isotherms are observed when this anion is dissolved in the subphase, which demonstrates that the polyanions interact with the monolayers. LB films have been readily obtained from this system. The adsorption Fourier transform IR (FT IR) spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD) and cyclic voltammetry (CV) have been used to investigate the morphological and molecular structure of the deposited film. The FT IR results showed the presence of the polyanion within the LB films, and the shift for its characteristic bands may be related to the presence of positively charged DODA. AFM measurement reveals that the LB films of DODA/(H2O)(CoP2W17O618)-P-II are regularly and uniformly deposited on the substrate. XRD experiments prove that the lamellar structure of the LB films of DODA/(H2O)(CoP2W17O618-)-P-II is well-defined. The LB films of DODA/(H2O)(CoP2W17O618-)-P-II immobilized onto an indium-oxide (ITO) glass, in aqueous solutions of pH 2.0-5.0, show quite facile redox reactions even for multilayers. All the experiments carried out in the present study suggest that the new materials of heteropolyanions can be formed by LB techniques and beneficial physicochemical properties of heteropolyanions can be maintained/enhanced through molecular-level design. (C) 1999 Elsevier Science S.A. All rights reserved.

Synthesis and structure of alpha-B-Keggin type heteropoly complex K5H[Co-4(VW9O33)(2)]center dot 5H(2)O

A new complex K5H[Co-4(VW9O33)(2)]. 5H(2)O was prepared and its structure was determined by X - ray diffraction analysis. The anion has alpha - beta - Keggin structure. Two (VW9O33)(7-) moieties (alpha - B isomers) are linked via four Co(11)O-6 groups. The single crystal of the title complex is monoclinic P2(1/n) with a = 1.2307(3) nm, b = 2.1250(4) nm, c = 1.5817(3) nm, beta = 91.86(3)degrees, V = 4.1343 (14) nm(3), R = 0.0895, R-w = 0.2180.

Synthesis and crystal structure of a polymeric erbium(III)-sodium(I) coordination complex of picolinic acid N-oxide

A new Er(III)-Na(I) coordination polymer of stoichiometry [NaEr2L5(H2O)(6)(NO3)](NO3). 3.5H(2)O (HL = picolinic acid N-oxide) has been synthesized and characterized by single-crystal X-ray analysis. Crystals are triclinic, P (1) over bar with a = 9.823(2), b = 12.453(2), c = 20.643(4) Angstrom; alpha = 98.49(3), beta = 101.40(3), gamma = 108.69(3)degrees; V = 2284(1) Angstrom(3); Z = 2. Of the two independent eight-coordinate erbium(III) ions in this complex, one is surrounded by four bidentate chelating L ligands, and the other by one bidentate chelating L ligand, four aqua ligands and two anti-carboxylate oxygen atoms from two neighboring [ErL4] units. The sodium(I) ion is in a distorted octahedral environment, being coordinated by a unidentate nitrate anion, three aqua ligands and two anti-carboxylate oxygen atoms from two adjacent [ErL4] units. The complex is built from zigzag chains of syn-anti carboxylate-bridged erbium(III) moieties directed in the a direction, which are cross-linked pairwise by aqua-bridged dimeric sodium(I) units. The resulting composite polymeric chains are further connected by hydrogen bonds to form a three-dimensional network.

In-situ microscopic FTIR spectroelectrochemical study of the reduction of K3Fe(CN)(6) in polymer electrolyte

Cyclic voltammetry and in-situ microscopic FTIR spectroelectrochemistry were used for the electrochemical and vibrational characterizations of the reduction process of K3Fe (CN)(6) in polyethylene glycol(PEG) with LiClO4 as supporting electrolyte at a Pt microelectrode. The rate of electron transfer is a function of the concentration of the supporting electrolyte. The redox potentials and cyclic voltammetric currents vary with Li/O molar ratio. The bl-situ spectroelectrochemistry shows that the infrared spectra are influenced by the concentration of LiClO4. The bridging cyanide groups with a structure Fe-I-C drop N ... Fe-I-C drop N are formed during the reduction process of K3Fe (CN)(6). There may be an activated complex between the Lif cation and the complex anion.

Synthesis and structure of [NH4](4)H[(PMo8V4V2O42)-V-IV-O-V].24H(2)O

[NH4](4)H[(PMo8V4V2O42)-V-IV-O-V] . 24H(2)O has been hydrothermally synthesized from ammonium vanadate and sodium molybdate in aqueous solution by adding phosphorous acid, and its structure determined by single crystal X-ray analysis. The heteropoly molybdovanadophosphate anion is a bicapped 'pseudo-Keggin' polyanion, two vanadium atoms are distributed at two 'capping' metal atom positions and other four vanadium atoms randomly distributed at eight metal atom positions. (C) 1998 Elsevier Science Ltd. All rights reserved.

[Ni(C10H8N2)(3)](2)[V4O12].11H(2)O

The crystal structure of the title compound, bis[tris(2,2'-bipyridyl-N,N')nickel(II)] cyclo-tetravanadate undecahydrate, contains a centrosymmetric [V4O12](4-) anion, which has an eight-membered ring structure formed by four VO4 tetrahedra sharing vertices, and two complex cations containing octahedrally-coordinated Ni-II ions. The anion and coordinated Ni-II ions are isolated and make up anion and cation layers, respectively. The Ni-N distances range from 2.077(3) to 2.112(2)Angstrom and the V-O distances range from 1.621(2) to 1.803(2)Angstrom.

Syntheses and structures of Na-2[Zn-II(ida)(2)].7H(2)O and Na-4[Hg-II(nta)(2)].7H(2)O

The title complexes were synthesized and the crystal structures of their salts were determined by single-crystal X-ray structure analyses. Na-2[Zn-I(ida)(2)]. 7H(2)O: Triclinic, P1, a=0.523 4(2) nm, b=0.897 10(10) nm, c=1.069 10(10) nm, alpha=85.910(10)degrees, beta= 76.380(10)degrees, gamma=83.52(2)degrees, V=0.484 2(2) nm(3), Z=1. The complex anion [Zn-I (ida)(2)](2-) has a pseudo-octahedral structure in which the two N atoms: are in a trans configuration. Na-4[Hg-I(nta)(2)]. 7H(2)O: Monoclinic, C-c, a = 1.795 0(4) nm, b = 0.892 9(2)nm, c = 1.575 4(2) nm, beta = 92.78 (3)degrees, V = 2.526 2(9) nm(3), Z = 4. The complex anion [Hg-I (nta)(2)](4-) has a pseudo-bicapped-octahedral structure in which the two N atoms are in a trans configuration.

Studies of ferrocene derivative diffusion and heterogeneous kinetics in polymer electrolyte by using microelectrode voltammetry

The heterogeneous electron transfer rate constants (k(s)) of seven ferrocene derivatives were estimated using cyclic voltammograms under mixed spherical/semi-infinite linear diffusion and steady-state voltammetry at a microdisk electrode in polymer electrolyte. The k(s) and diffusion coefficient (D) are both 100 to 1000-fold smaller in polymer solvent than in monomeric solvents, and the D and k(s) decrease with increasing polymer chain length. The results conform to the difference of viscosity (eta) or relaxation time (tau(L)) for these different solvents. The k(s) and D increase with increasing temperature, and the activation barriers of the electrode reaction are obtained. The influences of the substituting group in the ferrocene ring on k(s) and D are discussed. The k(s) are proportional to the D of the ferrocene derivatives, which indicates that solvent dynamics control the electrode reaction. (C) 1998 Elsevier Science S.A.

Electrochemical studies of a lanthanide heteropoly tungstate/molybdate complex in polypyrrole film electrode and its electrocatalytic reduction of bromate

An electrode modified with a polybasic lanthanide heteropoly tungstate/molybdate complex K10H3[Nd(SiMo7W4O39)(2)] entrapped into polypyrrole (PPy) film, denoted as Nd(SiMo7W4)(2)-PPy, exhibits three couples of two-electron redox waves in pH 1-5 buffer solutions. The redox waves are surface-controlled at lower scan rates and diffusion-controlled at higher scan rates. The effects of pH on the electrochemical behavior of Nd(SiMo7W4)(2) in PPy film were investigated in detail and compared with that of Nd(SiMo7W4)(2) in aqueous solution. The various charge states of PPy during its redox process have peculiar effects on the relationship between pH and formal potentials of Nd(SiMo7W4)(2)-PPy at different acidities. The Nd(SiMo7W4)(2)-PPy cme can remarkably catalyze the electrochemical reduction of bromate with good stability. (C) 1997 Elsevier Science Ltd.

Electrocatalytic oxidation and flow amperometric detection of hydrazine at an electropolymerized 4-vinylpyridine/palladium film electrode

A poly(4-vinyl)pyridine (PVP)/Pd film electrode was constructed for the electrocatalytic detection of hydrazine. The preparation of the PVP/GC electrode was performed by electropolymerization of the monomer 4-vinylpyridine onto the surface of a glassy carbon electrode. Subsequently, palladium is electrodeposited onto the polymer modified electrode surface. The ion-exchange function of PVP polymer is helpful to this process in view of the tetrachlorapalladate anion. Compared with the Pd/GC electrode, the modified electrode displays a better mechanical stability in a flowing stream. The PVP/Pd film electrode exhibits higher sensitivity when detecting hydrazine with a detection limit of 0.026 ng (S/N=3).

Synthesis, structure and properties of alpha-Keggin-type of K6H3[ZnW11O40Al]center dot 9.5H(2)O

A new heteropolycomplex, K6H3[ZnW11O40Al] . 9.5H(2)O was prepared and characterized by means of elemental analysis, IR, UV spectroscopy, Al-27 NMR, electrochemistry and X-ray crystallography. The crystal of K6H3[ZnW11O40Al] . 9.5H(2)O is cubic, space group Fm-3m, with lattice constants a=b=c=2. 144 8(2) nm, V = 9.866(2) nm(3), Mo radiation, R = 0.057 8 for 497 independent data with [I>2 delta(I)]. The anion is of alpha-type Keggin structure with C-s symmetry.

Synthesis, structure and properties of undecatungstozincate containing 3A elements

New compounds KaHb[ZnW11O39M(H2O)]. xH(2)O (M = Al, Ga or In) were prepared and characterized by elemental analysis, IR and UV and Al-27 NMR spectroscopy, electrochemistry and X-ray crystallography. In the crystals of K6H3[ZnW11AlO40]. 9.5H(2)O, the anion is of the alpha-type Keggin structure with C-s symmetry. The Al and W atoms are statistically distributed in the crystal. (C) 1997 Elsevier Science Ltd.