Co-ordination chemistry of mixed pyridine–phenol and phenanthroline–phenol ligands; a variable-temperature electron paramagnetic resonance and magnetic susceptibility study on two binuclear copper(II) complexes with Cu2(µ-O)2(µ-1,3,-O2CMe) cores

Abstract
The EPR spectra (characteristic of triplet species) of the complexes [Cu2L1 2(µ-1,3-O2CMe)][PF6]1[HL1= 6-(2-hydroxyphenyl)-2,2′-bipyridine] and [Cu2L2 2(µ-1,3-O2CMe)][PF6]2[HL2= 2-(2-hydroxyphenyl)-1,10-phenanthroline], previously structurally characterised as containing Cu2(µ-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.

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