Luminescence quenching of tris (4,4’- dimethyl- 2,2’-bipyridyl) ruthenium (II) complex with quinones in aprotic polar medium.

Abstract

The photoredox reactions of biologically important quinones with the excited state [Ru(dmbpy)₃]²⁺ (dmbpy = 4,4’ - dimethyl -2,2’- bipyridine ) complex proceed through photoinduced electron transfer reaction in DMF and have  been studied by luminescence quenching technique. The complex shows absorption and emission maximum at 458 nm and 608 nm.  It shows a lifetime of 164 ns in DMF.  The dynamic or static nature of the quenching is confirmed from the ground state absorption studies. The oxidative quenching of [Ru(dmbpy)₃]²⁺ complex by quinones is confirmed from the transient absorption spectra and also from the linearity of  the Stern - Volmer plot. The quenching rate constant (k_q) is highly sensitive to the nature of the ligand, the free energy change (DG⁰) of the reaction as well as the electron transfer distance. Structural effect plays an importance role in the photoinduced electron transfer reaction in DMF.