Magnetostructural correlations in bis(mu(2)-phenoxide)-bridged macrocyclic dinuclear copper(II) complexes. Influence of electron-withdrawing substituents on exchange coupling

Macrocyclic dicopper(II) complexes derived from 2,6-di(R)formylphenols and various linking diamines are surveyed and their magnetic and structural properties assessed. For those systems with ''flat'' dinuclear centers and no electronic perturbations associated with electron-withdrawing ligands or ligand groups, the complexes exhibit a ''straight-line'' relationship between exchange integral and phenoxide bridge angle. Within the angle range 98.8-104.7 degrees, 11 complexes are included with -2J in the range 689-902 cm(-1). When electron-withdrawing species are present, either as ligands or as groups bound to the macrocycle itself, considerable suppression of the antiferromagnetic exchange component is observed. Single-crystal X-ray diffraction studies are reported for three complexes. [Cu-2(L1)(H2O)(2)]F-2(CH3OH)(2) (1) crystallized in the triclinic system, space group <(P)over bar 1>, with a 8.1878-(5) Angstrom, b = 9.0346(7) Angstrom, c = 10.4048(7) Angstrom, alpha = 103.672(6)degrees, beta = 101.163(5)degrees, gamma = 104.017(5)degrees, and Z = 1. [Cu-2(L2)Cl-2] [Cu-2(L2) (H2O)(2)]Cl(ClO4). 5.5H(2)O (2) crystallized in the monoclinic system, space group P2(1)/n with a 14.4305(5) Angstrom, b = 24.3149(8) Angstrom, c = 18.6584(8) Angstrom, beta = 111.282(3)degrees, and Z = 4. [Cu-2(L3)(H2P)(2)]- (BF4)(2) (3) crystallized in the triclinic system, space group <(P)over bar 1>, with a = 8.6127(4) Angstrom, b = 8.6321(7) A, c = 10.8430(10) Angstrom, a = 74.390(10)degrees, beta = 86.050(10)degrees, gamma = 76.350(10)degrees, and Z = 2. Square pyramidal copper ion stereochemistries are observed in all cases, with axially coordinated halogens or water molecules. Strong antiferromagnetic exchange is observed for all complexes (2J = 784(8) cm(-1), Cu-O-Cu 103.65(10)degrees (1); -2J = 801(11) cm(-1), Cu-O-Cu 102.4(3), 107.5(3), 102.9(3), 106.1(3)degrees (2); -2J = 689(3) cm(-1), Cu-O-Cu 98.8(4)degrees (3)). The presence of electron-withdrawing CN groups on the periphery of the macrocyclic ligand leads to substantially reduced antiferromagnetic exchange.