Kinetics of Excimer Electrogenerated Chemiluminescence of Pyrene and 1-Pyrenebutyricacid 2-Ethylhexylester in Acetonitrile and an Ionic Liquid, Triethylpentylphosphonium Bis(trifluoromethanesulfonyl)imide

We describe the kinetics of excimer electrogenerated chemiluminescence (ECL) of a liquid pyrene derivative, 1-pyrenebutyricacid 2-ethylhexylester (PLQ) dissolved in a molecular solvent, acetonitrile (MeCN), and an ionic liquid, triethylpentylphosphonium bis(trifluoromethanesulfonyl)imide ([P2225][TFSI]). Pyrene was also used for comparison. To discuss the kinetics of the excimer ECLs, the photophysical and electrochemical properties and electronic states of PLQ and pyrene were revealed. The photoluminescence (PL) spectra, rate constants for the radiative transitions, and redox potentials of PLQ and pyrene dissolved in MeCN and [P2225][TFSI] suggest that as a solvent, [P2225][TFSI] behaves more polar than MeCN. By analyzing the PL decay curves, the rate constants to form the excimer were determined to be on the order of 109 and 107 M–1 s–1 in MeCN and [P2225][TFSI], respectively, which were limited by the diffusion. For neat PLQ (1.6 M), a delay of 0.3–0.4 ns for the excimer emission compared to the monome...