Attenuated total reflectance-fourier transform infrared microspectroscopy of copper(II) complexes with reduced dextran derivatives

Abstract

Dextran is a water-soluble, extracellular neutral polysaccharide with a linear flexible chain of α-(1 → 6)-linked α-D-glucopyranose units, in a single compounds. In alkali solutions Cu(II) ion forms complexes with reduced low-molar dextran (RLMD). The metal content and the solution composition depended on pH. The complexing process begins in weak alkali solution (pH > 7), and involves OH groups in C2 and C3 dextran monomer units. Synthesized copper(II) complexes with RLMD, of average molar mass Mw = 5000 g/mol were investigated by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and FTIR imaging microscopy. ATR-FTIR microspectroscopic data of synthesized complexes are rare in literature. The changes in intensity and width of the IR bands in region 1500-1000 cm−1 were related to changes in conformation and short-range interactions of the ligand dextran. FTIR microscopy images shows more and less ordered structures of the Cu(II)-RLMD complexes. ATR-FTIR microspectroscopic data shows homogeneity of the Cu(II)-RLMD samples and green color of the samples confirm existence of Cu(II) ions.