Synthesis and properties of a new tetraaza macrocyclic ligand containing one N-acetic acid pendant arm and its copper(II) and nickel(II) complexes

A new monofunctionalized tetraaza macrocycle C-meso-5,16-dimethyl-2,6,13,17-tetraazatricyclo-[16.4.0.0(7.12)]docosane-2-acetic acid (HL2), in which one acetic acid group is appended, was prepared by the one-step reaction of the tetraaza macrocycle C-Meso-3,14-dimethyl- 2,6,13,17-tetraazatricyclo[16.4.0.0(7.12)]docosane (L-1) with an excess of bromoacetic acid. The copper(II) and nickel(II) complexes of HL2 were synthesized and characterized. Two types of copper(II) complexes [Cu(HL2)](ClO4)(2) . 0.5H(2)O and [CuL2]ClO4 . SH2O (L-2 is a deprotonated form of HL2) can be isolated under acidic and basic conditions respectively. However, only one form of nickel(II) complex [NiL2(H2O)]ClO4 was isolated even under acidic conditions. The crystal structure of [Cu(HL2)](ClO4)(2) . 0.5H(2)O shows that the pendant acetic acid group is coordinated to the metal ion through the oxygen atom of the carbonyl unit; the complex has a somewhat distorted square-pyramidal coordination geometry. The acetic acid group in [Cu(HL2)](2+) is also coordinated to the metal ion in nitromethane, acetonitrile, and greater than or equal to 0.5 M HClO4 aqueous solutions, but is deprotonated to produce [CuL2](+) even in pure water. The macrocycle HL2 reacts with copper(IT) ions more slowly than L-1. Crystal data of [Cu(HL2)](ClO4)(2) . 0.5H(2)O: monoclinic, space group P2(1)/n with a = 8.197(1), b = 21.485(4). c = 16.339(7) Angstrom, beta = 91.78(1)degrees and Z = 4. (C) 1998 Elsevier Science S.A. All rights reserved.