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

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].