Complexes of Co(III) with l-sorbose and phenanthroline

l-Sorbose and two molecules of 1,10-phenanthroline form a complex with Co(III) which has the A configuration about Co(III), based on CD and ORD spectra. The 1H NMR signals of α-l-sorbopyranose and its mixed Co(III)(phen)2 complex have been assigned. Signals of H-6 and H-6′ of the sugar are shifted strongly upfield because of shielding by the aromatic residues, but shifts are much smaller for H-1 and H-1′. These observations are consistent with molecular modelling with MM2 parameters, which predicts that the most stable complex is the Λ diastereomer with complexation at positions 1 and 2. The characteristics of the NMR spectra and the predicted structure of the complex differ from those of the corresponding complex of d-fructose.