Ryszard Gryboś

Complexation between molybdenum(VI) and citrate: structural characterisation of a tetrameric complex, K4[(MoO2)4O3(cit)2]·6H2O

The complex anion obtained by crystallisation from an aqueous solution of molybdate and citric acid (H3cit) at pH ca. 3 is of the type (i), [(MoO2)4O3(cit)2]4−, as determined by X-ray analysis of the salt K4[Mo4O11(cit)2]·6H2O. Principal dimensions [ranges or means; estimated standard deviation (e.s.d.) 0.005 A] are: MoO 1.692–1.734; Mo–O(bridging) 1.886–1.948; Mo–O(hydroxy) 1.972(5); Mo–O(carboxylate) (unidentate) 2.185–2.318, (bridging) 2.296–2.333 A. The crystals are triclinic, space group P, a = 8.966(4), b = 12.319(6), c = 15.962(9) A, α = 89.34(4), β = 99.80(4), γ = 107.04(4)°, R = 0.041 for 4 399 observed [I/σ(I) 2.0] reflections. The complex is tetranuclear with the citrato-ligands co-ordinated through the deprotonated hydroxy group and the α-carboxy group to form five-membered chelate rings. One of the oxygens of the β-carboxylate groups bridges between two Mo atoms [Mo(1)–Mo(2) and Mo(3)–Mo(4)] whereas the other oxygen bridges between these dimers. The other β-carboxylate group is not co-ordinated to molybdenum but is protonated. The i.r. and Raman solid-state spectra are in agreement with this structure as well as a study in solution (Raman, 1H and 13C n.m.r. spectroscopy, molecular weight determination).

1:1 Molybdenum(VI) citric acid complexes

SummaryThe complexes obtained by crystallisation from an aqueous solution of molybdate and citric acid (H4cit) at pH 4–8 have Mo:cit ratio 1∶1. The new complexes have been characterised by a variety of methods in the solid state and in solution. On this basis two dimeric species, [(MoO2)2O(citH)2]4− and [(MoO2)2O(cit)2]6−, and a monomeric species [MoO3(cit)OH2]4− are proposed.

Determination of the most stable structures of selected hydroxypyrones and their cations and anions

Equilibrium geometries of selected hydroxypyrones were determined using quantum-mechanical calculations. Computations were performed for all possible structures of pyromeconic acid, maltol, ethylmaltol and kojic acid. Tautomerism of protonated and deprotonated (kojic acid) forms of the studied compounds were also taken into account. For all neutral tautomers of investigated compounds it was shown that the most stable was enolic form. Cationic species were created by protonation of the keto oxygen atom. In order to form stable kojic acid anion deprotonation of hydroxyl group on the pyran ring is preferred. Obtained results confirm that tautomeric equilibria in a gas phase were only slightly influenced by entropy.

Spacer-dependent structural and physicochemical diversity in copper(II) complexes with salicyloyl hydrazones: a monomer and soluble polymers.

Complexation of copper(II) with a series of heterodonor chelating Schiff bases (LL) of salicylic acid hydrazide and aliphatic or cycloaliphatic ketones affords soluble one-dimensional (1D) metallopolymers containing Schiff bases as bridging ligands. Single-crystal X-ray diffraction results reveal nanometer-sized metallopolymeric wires [Cu(μ-LL)(2)](n) with off-axis linkers and a zigzag geometry. Octahedrally coordinated copper centers, exhibiting a Jahn-Teller distortion, are doubly bridged by two Schiff-base molecules in the μ(2)-η(1),η(2) coordination mode. The use of dibutylketone with long alkyl chains as a component for Schiff base formation leads to a distorted square planar monomeric copper(II) complex [Cu(LL)(2)], as evidenced by its X-ray crystal structure. The compounds are characterized by elemental analyses and IR and UV-vis spectroscopy, as well as magnetic susceptibility and cyclic voltammetry measurements. Electrochemical studies on the complexes reveal an existence of polymeric and monomeric forms in solution and the dependence of Cu(II)/Cu(I) reduction potentials on alkyl groups of salicyloyl hydrazone ligands. Polymeric complexes form conducting films on Pt electrodes upon multicycle potential sweeps.

Electron-transfer kinetics and mechanism of the reduction of octacyanometallates(IV) (M = Mo, W) by hydroxide ion in aqueous solution

SummaryThe kinetics of the reduction of octacyanometallates(IV) in alkaline aqueous medium have been studied spectrophotometrically. The experimental results are in agreement with following rate law:-d[M(CN)inf8sup3−]/dt = kobs[M(CN)inf8sup3−]2[OH−][Na+] where kobs = 4.1 × 10−2M−3s−1 (Mo) and 4.0 × 10−4 M−3 s−1 (W). The rate data were used to calculate the thermodynamic activation parameters ΔH‡ and ΔS‡. A mechanism of the reaction is discussed.

Synthesis and study of oxovanadium(IV) complexes with dithiobis(2,4-pentanedione)

Abstract Two vanadyl complexes of dithiobis(2,4-pentanedione), H 2 acac 2 S 2 , with 1:1:1 (metal—acac 2 S 2 —L, where L = DMSO, py) stoichiometry have been characterized by elemental analysis, IR and optical spectral studies, field desorption mass spectrometry and magnetic susceptibility measurements. It is concluded that trinuclear complexes [VO(acac 2 S 2 )DMSO] 3 ( A ) and [VO(acac 2 S 2 )py] 3 ( B ) are formed, for which cyclic structural forms are proposed.

Novel vanadyl complexes with 2-hydroxy-3-methyl-2-cyclopenten-1-one

Two examples of novel vanadyl complexes of 2-hydroxy-3-methyl-2-cyclopenten-1-one, Hmcp, with 1:2 stoichiometry have been characterised by elemental analysis, i.r. and optical spectral studies. [VOCl2(H2O)(Hmcp)2] (1) contains neutral Hmcp coordinated to vanadium through a carbonyl oxygen and both molecules are trans to each other. [VO(mcp)2H2O] (2) contains the mono-anionic form of Hmcp. Both complexes have distorted octahedral geometry.

Crystal structure of [VOCl2(H2O)(C6H9O2)2] from powder diffraction data

Abstract Crystal structure of aquadichlorobis(2-hydroxy-3-methyl-2-cyclopenten-1-one) oxovanadium(IV)—VO6Cl2C12H16 was solved by powder diffraction method. Space group C2/c(15), a,b,c,β=19.777(5),9.570(2),8.442(2) A , 94.28(2)°, V=1591.62(4) A 3 . RF and Rwp are 10.0 and 12.1%, respectively. Even though investigated compound seems to be of interest in biochemistry, its crystal structure has not been solved up till now. Presented structure is the first example of complex compound of 2-hydroxy-3-methyl-2-cyclopenten-1-one ligand with a transition metal.

Bis(4,4′-dimethyl-2,2′-bipyridine)oxidovanadium(IV) Sulfate Dehydrate: Potential Candidate for Controlling Lipid Metabolism?

Vanadium is a trace element mainly connected with regulation of insulin metabolism which is particularly important in diabetes. In recent years, organic complexes of vanadium seem to be more interesting than inorganic salts. Nevertheless, the effect of vanadium on lipid metabolism is still a problematic issue; therefore, the main purpose of this study was to investigate the effect of 3 organic complexes of vanadium such as sodium (2,2′-bipyridine)oxidobisperoxovanadate(V) octahydrate, bis(2,2′-bipyridine)oxidovanadium(IV) sulfate dehydrate, and bis(4,4′-dimethyl-2,2′-bipyridine)oxidovanadium(IV) sulfate dihydrate in conjunction with high-fat as well as control diet in nondiabetes model on the following lipid parameters: total cholesterol, triglycerides, and high density lipoprotein as well as activity of paraoxonase 1. All of these parameters were determined in plasma of Wistar rats. The most significant effect was observed in case of bis(4,4′-dimethyl-2,2′ bipyridine)oxidovanadium(IV) sulfate dehydrate in rats fed with high-fat diet. Based on our research, bis(4,4′-dimethyl-2,2′-bipyridine)oxidovanadium(IV) sulfate dihydrate should be the aim of further research and perhaps it will be an important factor in the regulation of lipid metabolism.

Influence of Vanadium-organic Ligands Treatment on Selected Metal Levels in Kidneys of STZ Rats

The objective of the study was to investigate the effects of five organic vanadium complexes supplement and a small dose of insulin injection on V, Fe, Cu, Zn, Mn, Ca, and K level in the streptozotocin diabetic rat’s kidney during a 5-week treatment with the tested complexes. In all groups of animals, metal level in the lyophilized kidney organs was investigated by means of the proton induced X-ray emission method. Tissue vanadium level was naturally higher in vanadium-treated rats. The maximum level of vanadium was observed in the kidney (