Synthesis, structure and properties of a N 3 tridentate bis-imidazolyl ligand with copper(II)

Abstract

The synthesis of a new tridentate ligand, bis[2-(1-methylimidazolyl)methyl] amine, [B-MIMA], is described. The compound has been characterized by 1H and 13C NMR spectroscopy and mass spectrometry, and forms complexes with various copper(II) salts. Crystallographic studies have been completed on the blue product from the reaction of B-MIMA with copper(II) acetate, [Cu(B-MIMA)(CH 3COO)](ClO 4) ( 6). Crystal data for 6 are: triclinic, P1, a = 5.176(2), b = 8.489(3), c = 10.066(3) Å, α = 95.09(5), β = 95.72(3), γ = 102.37(4), V = 427.1 Å and Z = 1. The structure was solved using the Patterson method which revealed the position of the copper atom and successive difference Fourier syntheses which revealed the location of the remaining atoms. The atom positions were refined by least-squares methods producing a final agreement factor of R = 0.021 and R w = 0.029 for 1897 observed reflections. The structure consists of a polymeric acetate bridged network of distorted square-pyramidal copper(II) ions. The five coordinate geometry around each metal ion is a result of the bonding of three nitrogen atoms from the B-MIMA ligand and two oxygen atoms from different acetate ions. The acetate ions act as bidentate ligands bridging different copper ions and the resulting extended bridging network extends out the crystallograhic a axis. Spectroscopic, magnetic and electrochemical properties of the complex are described and compared with related compounds. The solution spectroscopic properties of 6 suggest that the square-pyramidal geometry of the metal ion in the solid-state is not retained in solution.