Synthesis, luminescence studies and structural characterization of new Co(II) and Cu(II) complexes based on phenanthridine as a ligand

Abstract

Four new complexes, [Co(phend)2Cl2] (1), [Co(phend)(ƞ2-NO3)2H2O].2phend (2), [Cu(phend)2Cl2] (3) and [Cu2(phend)2(μ-OAc)4] (4) have been synthesized by the reaction of two equivalent of phenanthridine (phend) ligand with one equivalent of CoCl2·6H2O (1), Co(NO3)2·6H2O (2), CuCl2·2H2O (3) and Cu(OAc)2·H2O (4), respectively. The complexes were fully characterized by elemental analysis, luminescence and IR spectroscopy, and their structures were studied by the single-crystal diffraction method. According to X-ray analysis, complex 1 (τ4 = 0.91) exhibits distorted tetrahedral geometry around Co(II) and complex 3 (τ4 = 0) presents a perfect square planar geometry around Cu(II). There is octahedrally distorted environment around the Co(II) center in complex 2 and the complex 4 consists of paddle-wheel binuclear Cu(II) tetracarboxylate units with Cu⋯Cu distance of 2.688 Å. There are intermolecular hydrogen bonding and π-π contacts (for complexes 1–4) and CH⋯π interactions (for complexes 1 and 2) which are effective in the stabilization of the crystal structure. The luminescence spectra of complexes 1 and 3 show that their emission bands are enhanced relative to the free phend ligand, while the emission spectrum of phend ligand is stronger than that of complexes 2 and 4. In addition, the luminescence spectra of all complexes in acetonitrile solution show that the intensity of their emission bands in complexes [Co(phend)2Cl2] (1) and [Cu(phend)2Cl2] (3) with chloride counterion ligands are stronger than that for free phend ligand, unlike the complexes 2 and 4, which have weaker emission than free ligand.