Syntheses, spectroscopic, structural characterization of Co(III) and Co(II) carboxylates and electron transfer reactions with ferrocene derivatives

Abstract

Herein we report five cobalt compounds; three compounds containing 5-nitroisophthalate viz. Bis{bis(2,2'-bipyridine-K sup(2) -N,N')(carbonato-K sup(2) -O,O')cobalt(III)}5-nitroisophthalate undeca-hydrate, [Co(bpy) sub(2) (CO sub(3))]2(5-nip).11H sub(2) O 1 synthesized by conventional steam bath reaction, while [Co(H sub(2) O) sub(3)(bpy)(5-nip)].H sub(2) O 2 and polymeric [Co(5-nip)(bpy)(H sub(2)O)] 3 prepared under autoclave conditions. The two compounds of 4-nitrobenzoic acid viz. Bis(2,2'-bipyridine-K sup(2) -N,N')(carbonato-K sup(2)-O,O')cobalt(III)} 4-nitrobenzoate pentahydrate, [Co(bpy) sub(2)(CO sub(3))](4-nba).5H sub(2) O 4 and [Co sub(2)(4-nba) sub(2)(bpy) sub(2)(H sub(2)O)4](4-nba) sub(2) 5 were also obtained by steam bath and autoclave reactions. These compounds were characterized by single crystal X-ray diffractometry, elemental, spectroscopic, magnetic and thermal methods. Compounds 1 and 4 were studied by XPS, NMR, CV and VSM, revealing +3 oxidation state of Co. 1 showed eleven lattice waters while five waters were observed in 4 due to the change in carboxylate ligand. A large number of O-H...O and C-H...O interactions leading to extended networks were observed their crystal structures. The thermal behaviour of 1-5 was investigated using TG-DTA techniques. Both carbonato Co(III) compounds 1 and 4 were investigated for their oxidizing properties with ferrocene derivatives and the results of these electron transfer reactions are reported.