Zero-phonon lines and luminescence line narrowing in the series Ru(bpy- d8) x(bpy) 3- x(PF 6) 2( x=1–3). Direct evidence for localization in the two lowest excited states

Abstract

Luminescence and excitation measurements were performed on single crystals of specifically deuterated compounds Ru(bpy- d 8) x (bpy) 3- x (PF 6) 2( x = 1–3) in the region of the sharp zero-phonon transitions at 4.2 and 2.1 K. The results are compared with the spectroscopic properties of the non-deuterated compound ( x=0). Strong evidence for the existence of localized, non-degenerate excited states is obtained. However, fast intramolecular excitation energy transfer takes place even at 2.1 K. This leads the excitation in theRu(bpy- d 8) x (bpy) 3- x (PF 6) 2( x=1–2) systems to be trapped on the protonated metal-ligand sub-unit(s) at temperatures below 10 K. Selective excitation allows luminescence as well as excitation features to be narrowed.