Three asymmetric Salamo-type copper(II) and cobalt(II) complexes: Syntheses, structures and fluorescent properties

Abstract

Three new supramolecular complexes, [Cu(HL1)] (1), [Cu(L2)H2O] (2) and [Co2(L2)2]·3CH3CN (3), were designed and synthesized by the reaction of 5-hydroxy-4′,6′-dibromo-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol (H3L1) with Cu(II) acetate hydrate (for 1); and 6-methoxy-4′,6′-dibromo-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol (H2L2) with Cu(II) acetate hydrate (for 2) and cobalt(II) acetate tetrahydrate (for 3), respectively, and were characterized by element analyses, X-ray crystallography, FT-IR, UV–Vis and fluorescence spectra. Complex 1 is mononuclear and tetra-coordinated and adopts a distorted square-planar geometry, likewise, complex 2 is mononuclear and penta-coordinated with a square-pyramidal geometry, however, complex 3 is dinuclear with the two Co(II) atoms having the same coordination environments and adopt a trigonal bipyramidal geometry. These self-assembling complexes form different dimensional supramolecular structures through inter- and intramolecular hydrogen bonds. Meanwhile, photophysical properties of the three complexes have also been discussed. Furthermore, the fluorescence behaviors of the two Cu(II) complexes in DMF are discussed.