Synthesis, spectroscopic and X-ray structural characterization of ternary complexes of copper(II) and 2,5-dimethoxycinnamic acid with phenanthrolines

Abstract

The complexes [Cu(dmc)₂L][Hdmc = 2,5-dimethoxycinnamic acid; L = 1,10-phenanthroline (phen), 4,7-dimethyl-1,10-phenanthroline (4,7-dmphen) or 2,9-dimethyl-1,10-phenanthroline (2,9-dmphen)] were synthesised and characterized by magnetic measurements, EPR and reflectance electronic spectroscopy. The crystal structure of [Cu(dmc)₂(2,9-dmphen)] has been determined by X-ray diffraction: it consists of discrete units [Cu(dmc)₂(2,9-dmphen)] in which a very asymmetric CuN₂O₂O′₂ chromophore is present with the two nitrogen atoms from 2,9-dmphen nearly symmetrically chelated [Cu–N 1.988(4) and 2.045(3)Å], two carboxylic oxygens of a bidentate dmc molecule [Cu–O 1.979(3) and 2.242(3)Å], and the oxygen atom of a monodentate carboxylic acid group of a second dmc molecule. Copper deviates from the 2,9-dmphen plane by 0.1811(7)Å and the carboxylic acid groups lie on planes roughly orthogonal [92.1(3)°]; the second carboxylic oxygen of the monodentate dmc molecule is involved in a long contact with the metal [Cu ⋯ O 2.959(4)Å].