Preparation and spectroscopic properties of cobalt(III), nickel(II), copper(II) and zinc(II) complexes with a novel saturated macrocyclic ligand: 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22-docosahydrodibenzo-[b,i][1,4,8,11]tetraazacyclotetradecine

Abstract

1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19, 20,21,22-Docosahydrodibenzo[b,i] [1,4,8,11] tetraazacyclotetradecine was prepared by hydrogenation of the benzo-analogue. Five isomers are feasible as a result of this hydrogenation but only two have been isolated: isomer A (melting point 158.5– 161.0 °C) and isomer B (melting point 194.5– 196.0 °C). The 13C NMR study was initiated to clear up the conformational differences between isomers. The cobalt(III), nickel(II), copper(II) and zinc(II) complexes of isomers A and B were prepared and investigated by near-ultraviolet, visible, infrared, NMR and ESR measurements. The ligand-field band in the 15 000-30 000 cm −1 region for the cobalt(III), nickel(II) and copper(II) complexes provided information on their geometry around the central metal atom. That is to say, the cobalt(III) complexes are subjected to the octahedral ligand-field with axial elongation. The copper(II) complexes and the nickel- (II) complex of isomer A are subjected to the square- planar ligand-field in these complexes. The ligand- field bands for the nickel(II)complex of isomer B display the square-planar-distorted octahedral equilibrium in the coordinating solvent. ESR measurements for the copper(II) complexes also presented the spin Hamiltonian parameters in accord with the square- planar coordination. A strong band appearing at ca. 3200 cm −1 was assigned to the N-H stretching mode and this band was slightly shifted to lower frequency upon metal coordination. The vibrational spectra and the conductance data provided evidences for the formation of the complexes with perchlorate ion as the counter ion. 13C NMR suggest that the complexes of isomer A are the cis-syn-cis form and the complexes of isomer B are the cis-anti-cis form.