Self-assembly of metal(II) tetraaza macrocyclic complexes with cyclobutane-1-carboxylic acid-1-carboxylate ligand linked by hydrogen bond

The reaction of [M(L)]Cl-2 center dot 2H(2)O (M = Ni2+ and Cu2+, L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0(1.18),0(7.12)]docosane) with 1,1-cyclobutanedicarboxylic acid (H-2-cbdc) generates 1D and 2D hydrogen-bonded infinite chains [Ni(L)(H-cbdc(-))(2)] (1) and [Cu(L)(H-cbdc(-))(2)] (2). (H-cbdc(-) = cyclobutane-1-carboxylic acid-1-carboxylate). These complexes have been characterized by X-ray crystallography, spectroscopy, and cyclic voltammetry. The crystal structure of 1 shows a distorted octahedral coordination geometry around the nickel(II) ion, with four secondary amines and two oxygen atoms of the H-cbdc(-) ligand at the trans position. In 2, the coordination environment around the central copper(II) ion shows a Jahn-Teller distorted octahedron with four Cu-N bonds and two long Cu-O distances. The cyclic voltammogram of the complexes undergoes two one-electron waves corresponding to M-II/M-III and M-II/M-I processes. The electronic spectra and electrochemical behavior of the complexes are significantly affected by the nature of the axial H-cbdc(-) ligand.