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 ](PF 6 ) 2 ( 1 ), [Ni(DMBPIP) 3 ](PF 6 ) 2 ( 2 ), [Co(DMBPIP) 3 ](PF 6 ) 2 ( 3 ), [Fe(DMBPIP) 3 ](PF 6 ) 2 ( 4 ), [Ru(DMBPIP) 3 ](PF 6 ) 2 ( 5 ) {where DMBPIP = 2-(3′,5′-dimethoxybiphenyl-4-yl)-1 H -imidazo[4,5- f ] [1,10]phenanthroline} were synthesized and characterized by means of elemental analysis, IR, 1 H NMR, 13 C{ 1 H} 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.