Phosphorescence quenching studies of bromoacetonaphthones in solution

Abstract

This paper is dedicated to Professor Ross Stebvart on the occasion of his 65th birthday ZDENEK HRUSKA, MARK C. PITON, and MITCHELL A. WINNIK. Can. J. Chem. 68, 1693 (1990). 4'-Bromo-1'-acetonaphthone (BAN) and 4'-bromo-1'-(1-dodecan0)naphthone (BLN) exhibit strong phosphorescence in degassed solutions in benzene. We report rate constants (k,) for phosphorescence quenching determined by phosphorescence quenching measurements for the following series of quenchers: pyrene, anthracene, tetracyanoethylene, p-dicyanobenzene, N,N-dimethylaniline (DMA), and N,N-dimethylamino-4-toluidine (DMAT). The first three quenchers quench at the diffusion-controlled rate. DMAT is 20-fold more effective as a quencher than DMA (k, = 1.4 X lo6 M-' s-I), but what is noteworthy is that both activation energies are very small, and quenching by DMAT is favoured over DMA mainly by entropic effects (AS' = -105 vs. -120 J mol-' K-I, respectively).