Investigation of structural characteristics of bis(β-diketonato)copper(II) complexes containing alkoxy or aryloxy side chains

Copper(II) complexes containing β-diketonato ligands of the general formula [Cu(4-RO)C ₆H ₄COCHCOC ₆H ₄(4-OR)} ₂] 3 (R = Bu) or 4 (R = Ph) were prepared and their structures solved by X-ray diffraction. The crystal structure of the parent ligand (4-BuO)C ₆H ₄COCH ₂COC ₆H ₄(4-OBu) 1 was also solved. The influence of the different side chains 4-RO - C ₆H ₄ (R = Bu or Ph) on potential liquid-crystal properties was investigated for both the ligands and the copper derivatives. The presence of BuO substituents at the aromatic rings appears to improve the molecular linearity with respect to 1,3-diphenylpropane-1,3-dione (=dibenzoylmethane; DBM), this feature being of interest for rod-like structures. On the other hand, the molecular structure of the copper(II) complexes 3 and 4 showed a flat core almost unmodified by the different peripherical substituents. A columnar arrangement was observed for both compounds 3 and 4, but, additionally, a layer-like disposition was also found in 3, which was proved to be a metallomesogen.