Spectroscopic, TG and DSC studies of lanthanide picrate complexes with 1,4-pyrazine-dioxide (pyzDO): crystal structure of the terbium complex

Abstract

Terbium(III), holmium(III) and erbium(III) picrate (pic) complexes with pyzDO with composition: [Ln(pic) (pyzDO) (H 2O) 6](pic) 2(pyzDO)(H 2O), were prepared by reaction of the respective hydrated picrates in ethanolic solutions with a water solution of pyzDO (molar ratio 1:2). The complexes were characterized by CHN microanalytical procedures, absorption infrared spectroscopy, X-ray powder patterns, single crystal structure of the terbium compound, TG and DSC studies. The Tb ion is coordinated to eight oxygen atoms, six of the water molecules, one of the pyzDO and the phenoxo oxygen of one pic moiety, giving rise to a bicapped trigonal prism. TG analyses indicate that water molecules are eliminated between 323 and 450 K followed by decomposition of pyzDO and picrates (628–743) and leaving Ln oxides as residues. DSC shows one endothermic peak due to water evaporation and two exothermic peaks due to decomposition of pyzDO and picrates.