T. Pandiyan et al., SYNTHESIS, STRUCTURE, SPECTRA AND REDOX ACTIVITIES OF MODEL COMPOUNDSFOR METHANOGENIC BACTERIA, Fresenius' journal of analytical chemistry, 354(5-6), 1996, pp. 636-640
Synthetically accessible benzimidazoles have been synthesized and the
benzimidazole ligands were complexed with nickel(II) nitrate. A nickel
(II) complex of N,N'-bis(benzimidazole-2-ylethyl)ethylenediamine was c
rystallized in single-crystal form and the structure was investigated
by X-ray crystallography, The structure of the complex is bicapped axi
al coordinated octahedral. Ni(bbes)(2)(2+) [bbes = bis(benzimidazole-2
-ylethyl)sulfide] exhibits broad low energy bands in electronic spectr
a and high redox potential in cyclic voltammetry (CV) rather than Ni(e
nbzim)(2+) [enbzim = N,N'-bis(benzimidazol-2-ylethyl)ethylene where hi
gh energy well separated bands were observed in the visible region and
a more negative redox potential was detected in CV. Experimental stud
ies show that an increasing amount of pi-orbital interaction with the
Ni(2+)ion, irrespective of chelate ring may favour the higher redox po
tential. The higher redox potential of methanogenic bacterial [Ni(II)/
Ni(I)] than nickel compounds is one of the main factors for the degrad
ation of organic biodegradable compounds and the further transformatio
n to methane.