Kyu-Chul Lee

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

Abstract The complexes [Ni(H2L)Cl2]Cl2·2H2O (2), [Ni2(L)2(N3)4]·5H2O (3) and [Ni(L)(tp)]·2H2O (4) (L=1,3,10,12,15,18-hexaazatetracyclo[16,2,1,112.15,04.9]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.

Synthesis and characterization of nickel(II) and copper(II) complexes with a tetramethyltetraaza macrocycle containing 2-pyridylmethyl pendant arms

Abstract The complexes [Ni(L2)](ClO4)2·H2O (1) and [Cu(L2)]Cl2·4H2O (2) have been synthesized and characterized by X-ray crystallography, electronic absorption and cyclic voltammetry. The crystal structure of 1 reveals a distorted octahedral geometry with four nitrogen atoms of the macrocycle and two nitrogen atoms of the pendant pyridylmethyl groups. The structure of 2 shows that the complex is centrosymmetric and the metal center has a tetragonally distorted octahedral environment. The electronic spectra and electrochemical behaviors of the complexes are significantly affected by the presence of the pendant arms.