title: Synthesis, characterisation and insulin-mimetic activity of oxovanadium(IV) complexes with amidrazone derivatives.
abstract: The complexation of VO(2+) ion by ten acetamidrazone and 2-phenylacetamidrazone derivatives (L) was studied. Sixteen novel VO(2+) complexes were synthesised and characterised through the combined application of analytical and spectroscopic (EPR (electron paramagnetic resonance), FT-IR and diffuse reflectance electronic absorption) techniques. Eight are 1:2 species of composition [VOL(2)]SO(4) x xH(2)O and eight are 1:1 species with formula [VOL(SO(4))](n) x xH(2)O. The experimental data suggest a bidentate coordination mode for L with the donor set formed by the imine nitrogen and the carbonyl oxygen. EPR spectra indicate a square-pyramidal geometry for the 1:1 complexes and a penta-coordinated geometry intermediate between the square-pyramid and the trigonal-bipyramid for the 1:2 species. The hyperfine coupling constant along z axis, A(z), of the 1:2 complexes exhibits a marked reduction with respect to the predicted value (approximately 148x10(-4)cm(-1) vs. approximately 170x10(-4)cm(-1)). IR spectroscopic evidence supports the presence of sulphate as a counter-ion in the 1:2, and as a bridging bidentate ligand in the 1:1 complexes. Insulin-mimetic tests on modified fibroblasts, based on a modified MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazoliumbromide) assay, performed on three of the bis-chelated and eight of the mono-chelated derivatives, indicate that they are biologically active. The similar hydro/lipophilicity and the lack of ligand substituents recognizable by cell membrane receptors prevent substantial differentiation in the insulin-mimetic action.
authors.affiliation: Department of Toxicology, University of Cagliari, Via Ospedale 72, I-09124 Cagliari, Italy.
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Cocco
authors.forename: Valentina
authors.initials: V
authors.lastname: Onnis
authors.forename: Gustavo
authors.initials: G
authors.lastname: Ponticelli
authors.forename: Beate
authors.initials: B
authors.lastname: Meier
authors.forename: Dieter
authors.initials: D
authors.lastname: Rehder
authors.forename: Eugenio
authors.initials: E
authors.lastname: Garribba
authors.forename: Giovanni
authors.initials: G
authors.lastname: Micera
mesh_terms: D000577:Amides / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D007094:Imides / Q000737:chemistry*; D018716:Molecular Mimicry; D017550:Spectroscopy, Fourier Transform Infrared; D017968:Vanadium Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000577:Amides; D007094:Imides; D017968:Vanadium Compounds