Alteration of molecular conformations and spectral properties for nickel(II), zinc(II) and copper(II) complexes having 3,8-di(thiophen-2′,2′′-yl)-1,10-phenanthroline ligands

Four transition metal complexes of 3,8-di(thiophen-2′,2″-yl)-1,10-phenanthroline (dtphen), formulated as [Ni(dtphen)2(H2O)2]·(ClO4)2 (1), [Zn(dtphen)2(H2O)]·(ClO4)2 (2) [Cu(dtphen)2(H2O)]·(ClO4)2 (3), [Cu(dtphen)(phen)2]·(ClO4)2 (4) (phen = 1,10-phenanthroline) with different metal-to-ligand ratios, were synthesized and characterized herein. The X-ray single-crystal diffraction studies of 1–4 exhibit that different molecular configurations for the dtphen ligand can be observed where the side thiophene rings adopt the trans/trans, trans/cis, trans/disorder and cis/cis conformations relative to the central 1,10-phenanthroline unit in different compounds. Fluorescence emission spectra of 1–4 in methanol show that the fluorescence emission of 2 is much stronger than the other three metal complexes, which is mainly due to its full d10 electronic configuration of Zn(II) ion.