Mixed complexes of cobalt(III) with phenanthroline and galactose or arabinose

Abstract

Mixed complexes of bis-phenanthroline cobalt(III) and α-D-galactose or β-D- or L-arabinose are identified in aqueous solution from their 1H NMR and circular dichroism (CD) spectra. Galactose forms only the Δ-complex, but D-arabinose gives preferentially Δ-, and L-arabinose preferentially Λ-complexes, consistent with structural optimization with PM3 (tm) parameters. The Λ-complex is formed initially from β-D-arabinose, but the Δ-complex is preferred thermodynamically. Examination of the absorption and CD spectra gives information on configuration at cobalt(III) and allows assignments of electronic transitions in Co(III) and the phenanthroline residues. © 2001 Elsevier Science Ltd. All rights reserved.