Spacer-armed copper(ii) complexes with benzenecarboxylic acids and trifluoroacetylacetone aroylhydrazones

Abstract

New bi- and trinuclear copper(II) complexes of aroylhydrazones of TFA and benzenecarboxylic acids were synthesized and characterized. Despite long range intramolecular Cu⋯Cu distances of about 10 Å, exchange couplings between paramagnetic centres are observed with J values of 0.33 and 0.37 cm⁻¹ in binuclear complexes, and −0.33 cm⁻¹ in trinuclear complexes. Seven hyperfine peaks with a value of a_Cu = 37.0 × 10⁻⁴ cm⁻¹ are observed in EPR spectra of binuclear complexes. The possible mechanisms responsible for the observed weak long range coupling via aromatic spacers are discussed.