ULTRAFAST EXCITED-STATE PROTON-TRANSFER FROM DICYANO-NAPHTHOL

The rate of proton transfer from electronically excited 5,8-dicyano-2- naphthol (DCN2) to the solvent is studied by time-resolved fluorescenc e, Unlike most naphthol derivatives, excited DCN2 is a strong acid (pK approximate to - 4.5) and therefore is capable of transferring proto ns to alcohols and other moderate proton acceptor solvents, The rate c onstant of proton transfer, kappa(d), at low temperatures (< 250 K) is slightly larger than the inverse dielectric relaxation time, 1/tau(D) and has the same activation energy of the dielectric relaxation. On t he other hand, at temperatures above 250 K the temperature dependence of the proton transfer rate decreases monotonically with increasing te mperature, while the dielectric relaxation activation energy maintains the low temperature value.