Vanadyl in natural waters: Adsorption and hydrolysis promote oxygenation

Several sal 2 en-type reduced Schiff bases have been prepared from the reaction of 2 equiv. of salicylaldehyde (or derivatives) with ethylenediamine followed by reduction with NaBH 4 and subsequently characterised. The water-soluble ligands (SO 3 -sal) 2 en and R(SO 3 -sal) 2 en (SO 3 -sal = salicylaldehyde-5-sulphonate) have been studied by pH potentiometry and 1 H NMR spectroscopy and the protonation constants of R(SO 2 -sal) 2 en have been determined. The Schiff bases are more susceptible to hydrolysis than the corresponding reduced Schiff bases. The crystal structures of H 2 (o-van) 2 en and KH(o-van) 2 en (o-van = o-vanillin) have been determined by X-ray diffraction. The vanadium(IV) complexes have been prepared and characterised by magnetic measurements and IR, UV/Vis and EPR spectroscopy. The colours, magnetic susceptibilities and IR spectra of the new vanadium(IV) complexes of the reduced Schiff bases now obtained suggest oligomeric/polymeric structures for the compounds while the corresponding V I V O-Schiff-base complexes are monomeric. The complexation of (V I V O] 2 + and (V V O 2 ] + with R(SO 3 -sal) 2 en in aqueous solution has been studied by pH potentiometry, UV/Vis as well as by EPR spectroscopy for the V I V O system and 1 H and 5 1 V NMR spectroscopy for the V V O 2 system. Complex formation constants have been determined and binding modes have been proposed. N,N'-ethylenebis(pyridoxylaminato) (Rpyr 2 en) has also been obtained and the structure of Na(V V O 2 (Rpyr 2 en)].CH 3 OH.3H 2 O determined by X-ray diffraction. The Rpyr 2 en 2 - ligand coordinates through both the N-amine and O-phenolate moieties in a symmetrical α-cis type coordination mode, i.e. with both O-phenolato donors cis to the O-oxo atoms and trans to each other.

/pdf/vanadium-iv-and-v-complexes-of-schiff-bases-and-reduced-4sf7gdr4po.pdf

Vanadium(IV and V) Complexes of Schiff Bases and Reduced Schiff Bases Derived from the Reaction of Aromatic o-Hydroxyaldehydes and Diamines: Synthesis, Characterisation and Solution Studies

Stabilization of Co (III) in aluminophosphate molecular sieve frameworks

Potentiometric (pH titrations) and spectroscopic (electron paramagnetic resonance) methods have been used to determine the thermodynamic stability constants of the various VO2+ complexes formed after the interaction of four insulin-enhancing vanadium compounds, [VO(6-mepic)2], cis-[VO(pic)2(H2O)], [VO(acac)2], and [VO(dhp)2], where 6-mepic, pic, acac, and dhp indicate the deprotonated forms of 6-methylpicolinic acid, picolinic acid, acetylacetone, and 1,2-dimethyl-3-hydroxy-4(1H)-pyridinone, with high molecular mass [human serum apotransferrin (hTf) and human serum albumin (HSA)] and low molecular mass (lactate) components of blood serum. In particular, log β values for the formation of (VO)hTf (13.0 ± 0.5), (VO)2hTf (25.5 ± 0.5), (VO)HSA (9.1 ± 1.0), (VO) 2d HSA (20.9 ± 1.0), cis-VO(dhp)2(hTf) (25.5 ± 0.6), cis-VO(dhp)2(HSA) (25.9 ± 0.6), (VO)hTf(lact) (14.5 ± 0.8), (VO)2hTf(lact)2 (28.5 ± 0.8), (VO)hTf(pic) (15.6 ± 0.8), and (VO)2hTf(pic)2 (30.4 ± 0.8) were determined. The values of the stability constants were used to compare the calculated composition of ternary and quinary systems with that recently proposed by some of us through electron paramagnetic resonance and density functional theory methods (Sanna et al. in Inorg. Chem. 49:174–187, 2010) and to predict the distribution of VO2+ ion in blood serum when one of the four insulin-enhancing vanadium compounds studied, [VO(carrier)2], is administered.

A quantitative study of the biotransformation of insulin-enhancing VO(2+) compounds.

Vanadium: History, chemistry, interactions with α-amino acids and potential therapeutic applications.

Hydrolytic behavior of oxovanadium(iv) ions

The reactions of tungstophosphate with cobalt ion and the properties of heteropolytungstates containing cobalt have been investigated. Unsaturated heteropolyanion PW11O397− produced by the partial degradation of the parent 12-tungstophosphoric acid reacts with cobalt ion to give 11-tungstocobaltophosphate PCoW11O40H25−. Discussion is given on the presence of cobalt in the heteropolyanion and on the above reaction. Both 12-tungstocobaltate-(II) and -(III) are very resistant to acid, but 11-tungstocobaltophosphates lose cobalt ion in strongly acidic solutions to give the parent 12-acid. Some aspects of the spectra of the heteropolytungstates, in which cobalt(II) and cobalt(III), respectively, are present in the specific site, are discussed.

Mutsuo Hayashi

Papers

Hydrolytic behavior of oxovanadium(iv) ions

Heteropolytungstates containing cobalt(II) or cobalt(III).

Heteropolytungstates containing cobalt(ii) or cobalt(iii)