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.