Phosphorescence quenching studies of bromoacetonaphthones in solution

4′-Bromo-1′-acetonaphthone (BAN) and 4′-bromo-1′-(1-dodecano)naphthone (BLN) exhibit strong phosphorescence in degassed solutions in benzene. We report rate constants (k q ) 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 q  = 1.4 × 10 6  M −1  s −1 ), but what is noteworthy is that both activation energies are very small, and quenching by DMAT is favoured over DMA mainly by entropie effects (ΔS ≠  = −105 vs.−120 J mol −1  K −1 , respectively). Keywords: aromatic ketone photochemistry, triplet exciplex.