A structural and magnetochemical study of some copper(II) complexes containing the ligands 1,4,7-triazacyclononane- N-acetate (L 1) and N-(2-hydroxybenzyl)-1,4,7-triazacyclononane (HL 2)

Abstract

The tetradentate macrocyclic ligands 1,4,7-triazacyclononane- N-acetate (L 1) and N-(2-hydroxybenzyl)-1,4,7-triazacyclononane (HL 2) react in methanol with CuCl 2 or Cu(ClO 4) 2·6H 2O in the absence or presence of LiOH·H 2O with formation of the following complexes containing square based pyramidal Cu(II)ions: [L 1CuCl] ( 1), [L 1CuCl]LiCl·2H 2O ( 2), [L 1Cu](ClO 4) ( 3) and [L 2 2Cu 2](ClO 4) 2 ( 4). Complexes 2 and 4 have been characterized by single crystal X-ray crystallography; the structure of 3 has been reported previously [3]. Crystal data: 2, space group P2 1/c, a = 11.674(4), b = 7.543(2), c = 17.560(5) A ̊ , β = 106.59(8)° , V = 1481.9(7) Å 3 Z = 4, D calc = 1.63 g cm −3, R = 0.044 based on 2499 reflections; 4, space group Pbca, a = 17.742(4), b = 10.335(2), c = 17.742(4) A ̊ , V = 3253(1) A ̊ 3, D calc = 1.62, Z = 4, R = 0.048 based on 2147 reflections. From temperature dependent magnetic susceptibility measurements (2–293 K) weak intermolecular antiferromagnetic exchange coupling has been established for 1 and 2, whereas for the helical chain structure 3 weak ferromagnetic exchange coupling has been observed. In dinuclear 4 strong antiferromagnetic intramolecular coupling leads to an S = 0 ground state.