Mixed-ligand copper(II) complexes with the rigid bidentate bis(N-arylimino)acenaphthene ligand: Synthesis, spectroscopic-, and X-ray structural characterization

Reported are the synthesis, characterization, and crystal structures of two mixed-ligand copper(II) complexes containing bis[N-(2,6-diisopropylphenyl)imino]acenaphthene (o,o′-iPr2C6H3-BIAN). In both complexes, namely [Cu(AcOH)(o,o′-iPr2C6H3-BIAN)Cl2] (1) and [Cu(acac)(AcOH)(o,o′iPr2C6H3-BIAN)] (ClO4) (2) (acac = acetylacetonate and AcOH = acetic acid), the copper ions are in a distorted square-pyramidal coordination environment with an acetic acid molecule in each apical position. The two imine nitrogen atoms of o,o′-iPr2C6H3-BIAN occupy the basal plane with the two chloride atoms and the two oxygen atoms of acac in complexes 1 and 2, respectively. Complex formation results in certain structural changes inside the rigid N-N ligand. Such changes led to an increased planarity of the o,o′-iPr2C6H3BIAN backbone, and produced a nearly perpendicular angle between the naphthalene and the aromatic imine planes. In complex 2, the more perpendicular arrangement of the o,o′-diisopropylphenyl groups shielding the copper centre was structurally allowed by the elongation of one of the metal-to-ligand bonds and by the relatively larger N-Cu-N bite angle. Also discussed are IR, magnetic, and UV/Vis measurements.