Abstract

Complexes of the type ?- and ?-[Co(diimine) 2carbohydrate]2+ were synthesized with the diimines: 1,10-phenanthroline and 2,2?-bipyridine and with the carbohydrates: aminosugars, hexoses, pentoses and sucrose, with the aim of finding out which are the determining factors of the resultant chirality in these compounds. The optical characteristics of the complexes obtained were determined through measurement of their absorption and circular dichroism spectra. All the complexes synthesized exhibited an excitonic effect in the UV spectral region. Assignment of the circular dichroism bands in the visible could be performed by applying ligand field theory treatment and assuming a D 2 local symmetry to the optically active bands in the region of the d-d* absorption bands corresponding to the 1A 1?1B2 and 1A 1?1B3 transitions. Rotatory strength of these bands can be ascribed to coupling of the magnetic moments of the d-d* bands with the electric moments of the ??? * transitions, polarized along the short axis of the diimine molecules, which turned out to be almost parallel in the ?- and ?-[Co(diimine)2carbohydrate]2+ complexes. © 2004 Elsevier Ltd. All rights reserved.