Synthesis and characterization of nickel(II) complexes of hexaazamacrotetracyclic ligand containing organic ligands

摘要

The complexes [Ni(H2L)Cl-2]Cl-2 (.) 2H(2)O (2), [Ni-2(L)(2)(N-3)(4)] (.) 5H(2)O (3) and [Ni(L)(tp)]. 2H(2)O (4) (L = 1,3,10,12,15,18-hexaazatetracyclo[16,2,1,1(12.15),0(4.9)]docosane; tp = terephthalate) have been synthesized and structurally characterized by X-ray crystallography, spectroscopic and cyclic voltammetry. The crystal structure of 2 has a distorted octahedral geometry with two secondary and two tertiary amines of the macrocycle and two chloride ions. In 3, the coordination geometry around the nickel atom is a distorted octahedral with four nitrogen atoms of the macrocycle and two nitrogen atoms of the azide groups. The nickel(II) ions in the complex 4 are bridged by the terephthalate anions to form infinite one-dimensional chain, which shows an elongated octahedral trans arrangement about each nickel(II) ion. The magnetic behavior of 4 exhibits a weak antiferromagnetic interaction with J value of - 1.18(3) cm(-1). Cyclic voltammetry of the complexes gives two one-electron waves corresponding to Ni(II)/Ni(III) and Ni(II)/ Ni(I) processes. The electronic spectra and redox potentials of the complexes also reveal a high-spin six-coordinated geometry, which is reflected by the nature of the organic ligands. (C) 2002 Elsevier Science Ltd. All rights reserved. [References: 23]