Ni(II), Cu(II) and Zn(II) complexes of a bifunctional bis(picolyl)amine (bpa) ligand derived from glycine

The reactions of the tripodal ligand bpaAc-Gly-OEt (1a) (bpaAc-Gly-OEt = (N ,N-bispicolylamino)acylglycine ethyl ester) with three different transition metal dihalides MCl2 (M = Ni, Cu, Zn) have been studied. 1a is a typical m ember of a new family of quadridentate amino acid derived ligands developed in our laboratories. X-ray crystal structures of the products [(bpaAc-Gly- OEt)NiCl2] (2), [(bpaAc-Gly-OEt)CuCl](2)[(H2O)CuCl3}Cl . 3H(2)O (3(2)[(H2O) CuCl3]Cl), and [(bpaAc-Gly-OEt)ZnCl](2)[ZnCl4] (4(2)[ZnCl4]) were obtained. The formation of octahedral (2), square-pyramidal (3), and trigonal-bipyra midal (4) coordination geometries demonstrates the flexibility of the quadr identate N3O ligand framework. A comparison with literature data reveals so me general trends in the chemistry of our amino acid ligands with different metal ions. The ligands are designed as building blocks for larger molecul ar and supramolecular assemblies. This report is part of our effort to stud y their basic coordination chemistry in order to gain insight in structural properties of aggregates based on synthetic metallopeptides. (C) 2001 Else vier Science B.V. All rights reserved.