SYNTHESIS AND STRUCTURE OF HETEROMETALLIC – MIXED-LIGAND Ge(IV) – 3d-METAL COMPLEXES WITH GALLIC ACID AND 1,10-PHENANTHROLINE

Abstract

Authors have developed optimal conditions and synthetic methods in water-organic solutions for ten heterometallic – mixed-ligand complexes of germanium(IV) and 3d-metals with gallic acid (Н2Gal) and 1,10-phenanthroline (phen), their composition and structure [M(phen)3][Ge(H2O)(HGal)2]∙nH2O (M = Mn (1), Co (2), Ni (3), Zn(5)); [CuCl(phen)2]2[Ge(H2O)(HGal)2]∙2H2O (4). Comparative analysis of their IR-spectra and spectra gallic acid and 1,10-phenanthroline with involvement diffuse reflection spectra allowed to establish coordination sphere of germanium and 3-metals. IR-spectra of complexes 1-5 are similar, therefore coordination of ligands in them is the same. Comparatively to the IR-spectrum of gallic acid, there are absent valence absorption bands of free carboxylic groups while two bands of asymmetric and symmetric oscillation of C-O groups in carboxylate ions CОО- appear in the spectra of complexes. Deformation bands d(Сarom-О-Н) are shifted to the low-frequency region for 50-40 cm-1, which indicates deprotonation and binding to the complexing agent of OH-groups from gallic acid. Appearance of deformation bands d(H2О) at 1625 сm-1 is characteristic for the coordination water in composition of complexes. Presence of coordination and crystalline water as well as unbonded OH-group are confirmed with the band n(Ge-О) at 620 сm-1. Thermal decomposition of mixed-metal complexes starts with an endothermic effect in the temperature range 80-160°С where elimination of certain number of water molecules takes place: two – for 1 and 4, three – for 2 and 5, four – for 3. On the thermogravigrams of all compounds one more endoeffect in the temperature range 160-220°С is presented, where removal of one coordination water molecule happens. It was established, that coordination polyhedron of germanium was formed by five oxygen atoms of deprotonated hydroxyl groups from two molecules of gallic acid and one water molecule in all compounds. Second ligand – 1,10-phenanthroline is coordinated to 3d-metal through heterocyclic nitrogen atoms with formation of cations with different composition [M(phen)3]2+ (M = Mn, Co, Ni, Zn) та [CuCl(phen)2]+.