Synthesis and characterization of a series of transition metal polypyridyl complexes and the pH-induced luminescence switch of Zn(II) and Ru(II) complexes

Abstract

Five new transition metal complexes, formulated as [Zn(DMBPIP)3](PF6)2 (1), [Ni(DMBPIP)3](PF6)2 (2), [Co(DMBPIP)3](PF6)2 (3), [Fe(DMBPIP)3](PF6)2 (4), [Ru(DMBPIP)3](PF6)2 (5) {where DMBPIP=2-(3′,5′-dimethoxybiphenyl-4-yl)-1H-imidazo[4,5-f] [1,10]phenanthroline} were synthesized and characterized by means of elemental analysis, IR, 1H NMR, 13C{1H} NMR, standard spectroscopy techniques and cyclic voltammetry. The pH effects on UV–Vis absorption and luminescence spectra of the Zn(II) and Ru(II) complexes are studied, and ground- and excited-state ionization constants of the two complexes are derived. The two complexes acting as pH-induced “off–on–off” luminescence switches through protonation and deprotonation in buffer solution at room temperature are studied and discussed as well.