Dinuclear Copper(II) Complex with Intramolecular O−H⋅⋅⋅O Hydrogen Bonding: Magneto-Structural Correlation for Acylhydrazone-Based Phenoxido Bridged Copper(II) Complexes

The μ-phenoxido-bridged dinuclear copper(II) complex, [Cu₂(L¹)₂(dmso)(MeOH)] (1), has been synthesized using N′-(4-(diethylamino)-2-hydroxybenzylidene)-1-naphthohydrazide (H₂L¹) as ligand. The structural analysis of 1 reveals that the coordination geometry at the copper ions is best described as a square pyramidal with a Cu⋅⋅⋅Cu distance in the dinuclear complex of 303 pm which is supported by hydrogen bonding between the two apical oxygen donor ligands (O⋅⋅⋅O 277 pm). Magnetic studies indicate that 1 exhibits a strong antiferromagnetic interaction between the two copper(II) ions with a coupling constant of J=−450 cm⁻¹ ($$ ). The magnetic exchange is transmitted through the central [Cu₂(OR)₂]²⁺ core, a fragment for which different magneto-structural correlations have been reported depending on the substituent at the bridging oxygen atom. However, the properties of complex 1 cannot be explained by any of the established correlations. Nevertheless, complex 1, together with the series of compounds based on an acylhydrazone ligand framework reported so far, shows a magneto-structural correlation as a function of the Cu−O−Cu bridging angle that significantly differs from all previously reported.