Quenching dynamics study on photoinduced excited triplet duroquinone by TEMPO in 1,2-propandiol

Abstract

Chemically induced dynamic electron polarization (CIDEP) spectrum and transient absorptive spectrum are recorded in photolysis of duroquinone (DQ) in 1,2-propanodiol (PG). Durosemiquinone neutral radical DQH • and PG ketyl radical CH 3 _ COHCH 2 OH are produced through hydrogen transfer reaction from PG to 3 DQ*. When stable radical TEMPO is added to DQ/PG solution, photolysis results in CIDEP on TEMPO, which can be interpreted as a quartet precursor radical-triplet pair mechanism (QP-RTPM). There is competition between PG and TEMPO to quench 3 DQ*. The CIDEP intensity of DQH • decreases with the increase of TEMPO concentration. The quenching dynamics in photolysis of DQ/TEMPO/PG system is analyzed in detail. Based on the dynamics analysis and the measurement of the lifetime of 3 DQ* by its transient absorbance decay, the quenching rate constant of 3 DQ* by TEMPO in PG is obtained as 1.34 9 10 7 L mol -1 s -1 . This quenching rate constant is closely diffusion-controlled.