COORDINATION CHEMISTRY OF MIXED PYRIDINE PHENOL AND PHENANTHROLINE PHENOL LIGANDS, A VARIABLE-TEMPERATURE ELECTRON-PARAMAGNETIC RESONANCE AND MAGNETIC-SUSCEPTIBILITY STUDY ON 2 BINUCLEAR COPPER(II) COMPLEXES WITH CU2(MU-O)2(MU-1,3-O2CME) CORES

The EPR spectra (characteristic of triplet species) of the complexes [Cu2L12(mu-1,3-O2CMe)][PF6] 1 [HL1 = 6-(2-hydroxyphenyl)-2,2'-bipyridine] and [Cu2L22(mu-1,3-O2CMe)] [PF6] 2 [HL2 = 2-(2-hydroxy-phenyl)-1,10-phenanthroline], previously structurally characterised as containing Cu2(mu-O)2 cores in which the phenolate oxygen atoms of L1 and L2 bridge both copper(II) centres, have been successfully modelled using a perturbation-theory approach. The Cu ... Cu distances calculated from the spectra are in reasonable agreement with the values given by the crystal structures. By measuring the variation in intensity of the spectrum of 1 with temperature it was established that 1 is antiferromagnetic with J = 52 +/- 8 cm 1. Variable-temperature magnetic susceptibility measurements on 1 and 2 confirm the presence of moderate antiferromagnetic couplings, although the presence of a mononuclear impurity in each case precludes use of the Bleaney-Bowers equation to obtain more accurate values of J.