Competitive geminate quenching and geminate recombination reactions of 1‐naphthol

Abstract

The back proton recombination following the photo‐dissociation of 1‐naphthol was studied by a time‐correlated single‐photon counting apparatus. The measured picosecond time‐resolved fluorescence decay profiles were analyzed using the numerical solution of the Debye‐Smoluchowski equation with coupled reversible and irreversible proton back‐recombination reactions at the source. A full kinetic analysis shows that both the reversible geminate recombination reaction, which assumes at long times a t−3/2 dependence, and the irreversible geminate quenching reaction, which assumes at long times a t−1/2 dependence, are significant in determining the excited‐state kinetics of 1‐naphthol.

Controlling reactivity by remote protonation of a basic side group in a bifunctional photoacid

“…The dynamics of fluorescence were fitted by convoluting exponential functions which are solutions of rate equations with the instrument response function and then best-fitting the synthetic rime-resolved reaction curves with the measured one. A similar asymptotic t À3/2 power-law decay was observed for many OH photoacids [33][34][35][36][37][38][39][40][41][42][43][44] and was rationalized analytically by invoking a diffusion assisted reversible geminate recombination model. 3.…”

“…[37][38][39] In this case, two competing proton recombination reactions were observed. [37][38][39] In this case, two competing proton recombination reactions were observed.…”

“…[37][38][39] In this case, two competing proton recombination reactions were observed. [37][38][39]48 Pines et al 39 developed a kinetic model, which, by means of steadystate measurements combined with simple kinetic arguments, allowed a full kinetic analysis of the two coupled geminaterecombination reaction. [37][38][39]48 Pines et al 39 developed a kinetic model, which, by means of steadystate measurements combined with simple kinetic arguments, allowed a full kinetic analysis of the two coupled geminaterecombination reaction.…”

Solvent Assisted Photoacidity

“…(12.15)) in the case of selfquenching [49][50][51][52][53]58]) have demonstrated the general microscopic validity of K * a , even in a most demanding situation where the excited state is rapidly quenched back to the ground state. s 0 and s¢ 0 are the fluorescence lifetime of the photoacid and photobase, respectively, in the absence of proton transfer.…”

Design and Implementation of “Super” Photoacids

“…For 1-naphthol the lowest energy state is L a and for 2-naphthol L b . The photophysics of 1-naphthol is complicated by a pronounced proton quenching, which is manifested by the near absence of neutral fluorescence at all pHs and by a pK a * of 0.5 [11]. Years ago, we postulated that forward proton transfer to give 1-naphtholate was accompanied by reprotonation in the distal ring.…”