Synthesis, characterization and emission study of zinc(II) and cobalt(II) complexes: Bis(bidentate) iminophenols as zinc(II) selective fluorescence probes

Two zinc(II) complexes, [ZnII2(L1)2] (1) and [ZnII2(L2)2] (2), and two cobalt(II) complexes, [CoII2(L1)2] (3) and [CoII2(L2)2] (4), (H2L1 = iminophenol derived from the condensation of 4-aminobenzylamine and salicyldehyde, H2L2 = Schiff-base of 4-aminobenzylamine and 3,5-di-tert-butylsalicyldehyde) supported by bis(N,O-bidentate) ligands have been synthesized and characterized. X-ray single crystal structures of 3 and 4 revealed the dimeric nature of the complexes with a 1:1 ratio of metal and ligand. The zinc(II) complexes have a very similar composition as established from different analytical and spectroscopic techniques. The iminophenols exhibit highly selective fluorescence enhancement with high quantum yield upon binding with Zn2+ in solution. A 50-fold enhancement of emission in zinc(II) complexes is observed with respect to free iminophenols.

Graphical abstractBis(bidentate) iminophenol ligands stabilize dinuclear zinc(II) complexes that show high fluorescence emission. The iminophenols are efficient zinc(II) selective fluorescence probes.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Syntheses and characterization of zinc(II) and cobalt(II) complexes of bis(bidentate)iminophenols. ► Crystal structures of iminophenols and cobalt(II) complexes. ► Emission study of zinc(II) complexes in solution. ► Emission of the zinc(II) complexes in visible region with high quantum yield. ► Zn2+ selective fluorescence behavior of iminophenols.