Supramolecular interactions between a barbiturato copper(II) complex and 2,6-bis(alcanoylamino)pyridines

Bis(5,5-diethylbarbirurato)bis(pyridino) copper(II) was allowed to interact with a series of three 2.6-bis(alcanoylamino)pyridines of increasing aliph atic side-chain length, both in solution and in the solid stare. The interm olecular interactions, mainly heteromeric or homomeric hydrogen bonding, we re studied by FT-IR spectroscopy. In chloroform solution, the barbiturato c opper(II) complex formed hydrogen bonded associates with all of the above m entioned pyridine derivatives. In the solid state though, formation of hete romeric hydrogen bonded species was clearly observed only for the two pyrid ine derivatives incorporating the shorter aliphatic side chains. A possible structure of the resulting supramolecule is proposed. It is concluded that the enhanced dispersive forces originating from the longer aliphatic side chains of the pyridine derivatives influence the overall balance of intermo lecular forces in the solid state, so as to inhibit heteromeric hydrogen bo nd association in favor of "self association" of the interacting molecules. (C) 2001 Elsevier Science B.V. All rights reserved.