Excited-state proton transfer of weak and medium-strength photoacids in confined methanol-in-oil reverse micelles

Abstract

This study explores the excited-state proton transfer (ESPT) dynamics of weak and medium-strength photoacids, 8-hydroxypyrene-1,3,6-trisulfonic trisodium salt (pyranine; HPTS), D-luciferin, and 2-cyano-6-hydroxybenzothiazole (CBTOH), confined within water-in-oil and methanol-in-oil reverse micelles (RMs). We extend the previous work on the ESPT dynamics of HPTS in Igepal RMs to several weak or medium-strength photoacids confined in the RMs. These photoacids exhibit proton transfer rate constants on the order of 109 s-1 in small RMs, which are comparable to the solvation dynamics inside the RMs. This suggests that the solvation dynamics govern the ESPT rates in the RMs, irrespective of the core polar solvent characteristics.