Co-ordination behaviour of N-protected amino acids. Structural and spectroscopic study of complexes of CoII, NiII and CuII with N-(4-aminobenzoyl)glycine

Abstract

The structural and spectroscopic properties of complexes of N-(4-aminobenzoyl)glycine (HL) with Co^II, Ni^II and Cu^II have been investigated. The complex [{CoL₂(H₂O)₂}_n]·2nH₂O crystallizes in the space group P, with a= 8.027(2), b= 8.031(2), c= 10.033(1)Å, α= 96.52(2)°, β= 100.17(2)°, γ= 119.19(2)° and Z= 1; the nickel(II) homologue is isomorphous. The complex [(CuL₂)_n]·4nH₂O crystallizes in the space group P2₁/n, with a= 4.673(1), b= 20.476(1), c= 12.026(1)Å, β= 97.38(2)° and Z= 2. The cobalt(II) co-ordination geometry is tetragonally distorted octahedral with four oxygens from two water molecules and two carboxylate groups in the basal plane and two amino nitrogens in the apical position. The copper(II) complex shows a strongly distorted tetragonal-octahedral geometry with two oxygens and two amino nitrogens of different amino acidate anions in the basal plane and two oxygens in the off-z-axis position. The ligand acts as bidentate bridging giving rise to a polymeric one-dimensional chain in the cobalt(II) complex and two-dimensional layers in the copper(II) one.