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))

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 CuCl2 or Cu(ClO4)(2) . 6H(2)O in the absence or presence of LiOH . H2O with formation of the following complexes containing square based pyramidal Cu(II)ions: [L(1)CuCl] (1), [L(1)CuCl]LiCl . 2H(2)O (2), [L(1)Cu](ClO4) (3) and [L(2)(2)Cu(2)](ClO4)(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) Angstrom, beta = 106.59(8)degrees, V = 1481.9(7) Angstrom(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) Angstrom, V = 3253(1) Angstrom(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.