Sucrose bis(1,10-phenanthroline)cobalt (III). Predicted distortion at the octahedral center

Abstract

The two 1,10-phenanthroline ligands in the mixed Delta-cobalt(III) complex with sucrose are in different environments relative to the sucrose ligand as shown by differences in their H-1 NMR signals and predicted by structural optimization. There is considerable congestion between the glucose moiety and one of the phenanthrolines in the A-complex, and the interactions which stabilize it, relative to a A-complex, are analyzed. Differences in H-1 chemical shifts of the phenanthrolines are related to their mutual interactions and those with the glucose moiety of the sugar, which lead to pi-shielding in some of its H-1 NMR signals. Absorption and circular dichroism (CD) spectra are analyzed with assignment of the electronic transitions.