Solvent?Controlled Intermolecular Proton?Transfer Follows an Irreversible Eigen?Weller Model from fs to ns

Intermolecular Proton Transfer (PT) dynamics can be best studied by optical spectroscopy, which cover the vast timescale spanned process. PT in a hydrogen bonding complex between pyranine-based photoacid and trialkyl-phosphine oxide is addressed. The photoreaction traced with help of femtosecond transient absorption picosecond-resolved fluorescence. Characteristic kinetics spectra intervening species are isolated global analysis spectral decomposition time-resolved It found that shared proton shifts towards phosphine site upon photoexcitation acetonitrile. process occurs on sub-picosecond timescale, essentially, under solvent control. Despite ultrafast rate, an equilibrium hydrogen-bonded ion pair (HBIP) established. Further reaction steps delayed to nanosecond where formation excited deprotonated form observed. far-reaching consistency various methods supports irreversible Eigen-Weller mechanism state.