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

چکیده مقاله

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 C[sbnd]H⋯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. © 2020 Elsevier B.V.