Perturbation of the intramolecular hydrogen bonds of glucose by Cu+ association

A density functional theory study of glucose and glucose-Cu+ complexes has been performed to investigate the changes undergone by the set of intramole cular hydrogen bonds of the neutral system upon Cu+ association. The geomet ries of the different species investigated were optimized at the B3LYP/6-31 G(d,p) level. The same level of theory was used to obtain the harmonic vibr ational frequencies and to analyze the electron charge density by means of the atoms in molecules theory. We have shown that the interaction with Custrongly perturbs the set of intramolecular hydrogen bonds of the neutral. Some of these changes are a direct consequence of the conformational change s induced by the metal, which result in the breaking of some of the existin g bonds or in the formation of new ones. The most important point, however, is that the intramolecular hydrogen bonds that remain are perturbed to a d ifferent extent. In general, all hydrogen bonds in which the OH donor inter acts directly with the metal cation are significantly stabilized while the remaining ones become weaker. These changes influence the relative stabilit y of the complexes as well as its capacity to interact with other systems. (C) 2002 John Wiley & Sons, Inc.