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 (H^=-JS^1S^2 ${\widehat{{\rm H}}=-J{\widehat{{\rm S}}}_{1}{\widehat{{\rm S}}}_{2}}$). 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. [ABSTRACT FROM AUTHOR]