Cyclic and square wave voltammetry of chitooligosaccharides modified by osmium(VI) tetramethylethylenediamine

Abstract

Compounds containing vicinal diol (glycol) groups, including saccharides, could be modified with sixvalent osmium complexes with nitrogenous ligands, particularly with N,N,N′,N′-tetramethylethylenediamine (Os(VI)tem). The modification products are electrochemically active. Here we show that aminosaccharides can also be modified by Os(VI)tem. We studied chitosan oligosaccharides in their acetylated and deacetylated form in 0.2 M Na-phosphate, pH 6.9. Deacetylated chitosan oligosaccharides with free amino groups modified by Os(VI)tem yielded two peaks (peak I′ at −0.15 V and peak II′ at about −0.38 V) despite the fact that these oligomers contain only one glycol group on the non-reducing end of the molecule. The electrochemical behavior of Os(VI)tem modified deacetylated chitosan oligomers differs from Os(VI)tem modified simple saccharides, containing only glycol groups, predominantly in peak I′. Our results suggest that free amino groups are involved in Os(VI)tem modification of chitosan oligomers.