Synthesis and characterization of new addition compounds of bis(substituted-salicylaldehydo) cobalt(II) with 2,2′-bipyridine (bipy). Crystal and molecular structures of [Co II(3-methoxy-salicylaldehyde) 2(bipy)] · CH 3OH ( 1) and [Co II(bipy) 3]Br 2 · 0.5(5-chloro-salicylaldehydeH) · 1.5CH 3OH ( 5)

Abstract

The cobalt(II) addition compounds [Co(X-salo) 2(bipy)], where X-salo is the anion of substituted salicylaldehydes (X = 3-OCH 3 ( 1); 5-CH 3 ( 2); 5-Cl ( 3); 5-NO 2 ( 4)) and bipy the neutral 2,2′-bipyridine, were synthesized and characterized by physicochemical and spectral (IR, UV–Vis) data. Theoretical calculations (DFT, ZINDO) with gaussian-03 for the prediction of the electronic spectrum for the compound 1, gave good correlation with the experimental one in the solid state. The absorption spectra at different solvents showed that the compound is stable in CH 3CN, but unstable in CH 3OH and DMF solutions. The cyclic voltammetry study in CH 3CN gave all the expected waves for the redox processes of the metal Co(II) and the ligands bipy and salicylaldehydes. The compound 1 is very stable at ambient temperature but unstable upon heating decomposing to CoO at 980 °C in nitrogen, but at 500 °C in oxygen atmosphere. The X-ray diffraction study of the compound 1 verified the proposed octahedral arrangement of the ligands around the cobalt(II) atom. Along with the main products ( 1– 4), a side product ( 5) verified by X-ray diffraction study as [Co II(bipy) 3]Br 2 · 0.5(5-chloro-salicylaldehydeH) · 1.5CH 3OH.