Interaction of CoII, NiII and CuII with active aldehyde derivatives of thiamine

Abstract

The reactions of the chloride salts of Co^II, Ni^II and Cu^II with the ‘active aldehyde’ derivatives of thiamine, 2-(α-hydroxybenzyl)- and 2-(α-Hydroxycyclohexylmethyl-3-(4-amino-2-methylpyrimidin-5-ylmethyl)-5-(2-hydroxyethyl)-4-methylthiazolium (hbt and hcmt), were studied in methanolic solutions. Compounds of formulae [Co(hbt)Cl₃], [Co(hcmt)Cl₃], [Co(hcmt)Cl₃], [Ni(hbt)Cl₃]·2H₂O, [CuL′Cl₂]·H₂O and Cu₂(HL′)Cl₄·MeOH (L′= thiochrome) were isolated as solid adducts and characterized by elemental analysis conductivity, magnetic susceptibility, IR, UV/VIS and ESR spectra. Pseudo-tetrahedral structures with the metal co-ordinated through the N(1′) site of the ligands are proposed for the first three complexes. Both copper complexes contain thiochrome produced by oxidation of thiamine by Cu^II and the first one is proposed to have a pseudo-tetrahedral structure with the metal again bonded through N(1′), while the second is proposed to be a mixed-valence compound, with possible formula [Cu^l(HL′)Cl]⁺[Cu^IICl₃(MeOH)]^–.