Synthesis, Characterization, and Acid - Base Properties of Ruthenium(II) Complexes Containing N-ethyl-4-([1,10]-phenanthroline[5,6 - f]imidazol-2-yl)carbazole

Abstract

Three new ruthenium(ii) polypyridyl complexes, [Ru(phen)2(Hecip)]2+ (1), [Ru(phen)(Hecip)2]2+ (2), and [Ru(Hecip)3]2+ (3) complexes (phen = 1,10-phenanthroline, Hecip = N-ethyl-4-([1,10]-phenanthroline[5,6–f]imidazol-2-yl)carbazole) were synthesized and characterized by ES-MS, 1H NMR spectroscopy, elemental analysis, and cyclic voltammetry. The emission spectra of complexes were measured both at room temperature and at 77 K in a 4/1 (v/v) EtOH/MeOH matrix. All three complexes display luminescence properties which are close to that featured by the parent [Ru(phen)3]2+ species. The pH effects on the UV-vis and emission spectra of RuII complexes were also studied, and complexes 1, 2, and 3 were found to act as ‘on–off’ luminescent pH switches with maximum on–off ratios of 17, 230, and 90, respectively.