Chiral Monomeric and Homochiral Dimeric Copper(II) Complexes of a New Chiral Ligand, <i>N</i>-(1,2-Bis(2-pyridyl)ethyl)pyridine-2-carboxamide: An Example of Molecular Self-Recognition

Reaction of Cu(ClO4)2·6H2O with a racemic mixture of the novel chiral ligand N-(1,2-bis(2-pyridyl)ethyl)pyridine-2-carboxamide (PEAH) affords only the homochiral dimeric copper(II) complexes [Cu2(RPEA)2](ClO4)2 and [Cu2(SPEA)2](ClO4)2 in a 1:1 ratio. The phenomenon of molecular self-recognition is also observed when a racemic mixture of the monomeric copper(II) complex [Cu(R(S)PEA)(Cl)(H2O)] is converted into the homochiral dimeric species [Cu2(R(S)PEA)2](ClO4)2 via reaction with Ag+ ion. This is the first report of direct conversion of a racemic mixture of a chiral monomeric copper(II) complex to a mixture of the homochiral dimers.