title: Proton-Coupled Electron Transfer in a Hydrogen-Bonded Charge-Transfer Complex.
abstract: A proton-coupled electron transfer (PCET) reaction in a hydrogen-bonded charge-transfer (CT) complex of 4-([2,2'-bipyridin]-4-yl)phenol (bpy-phenol) with a F-ion has been investigated by ultrafast time-resolved transient absorption spectroscopy. The phenolic receptor molecule, bpy-phenol, binds to the F-ion through a hydrogen bond and senses the F-ion via the Stokes-shifted CT band. Upon photoexcitation, CT from the phenol residue to the bpy residue promotes proton transfer from the phenol radical cation (ArOH•+) to the fluoride ion at ultrafast time scales of <150 fs (instrument response function limited) and 3 ps, separately. The fast and slow proton-transfer times are linked to two different types of hydrogen-bonding networks between the phenol residue and fluoride ion. Crystalline water in the fluoride salt hydrates mediates the proton-transfer reaction. This work demonstrates the participation of a hydrogen-bonded water bridge within a PCET reaction in a water-restricted environment.
authors.affiliation: Radiation and Photochemistry Division, Bhabha Atomic Research Centre , Mumbai 400085, India.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Verma
authors.affiliation: CSIR-National Chemical Laboratory , Pune 411008, India.
authors.forename: Sunil
authors.initials: S
authors.lastname: Aute
authors.affiliation: CSIR-National Chemical Laboratory , Pune 411008, India.|CSIR-Central Salt and Marine Chemicals Research Institute , Bhavnagar 364002, India.
authors.forename: Amitava
authors.initials: A
authors.lastname: Das
authors.affiliation: Radiation and Photochemistry Division, Bhabha Atomic Research Centre , Mumbai 400085, India.
authors.forename: Hirendra N
authors.initials: HN
authors.lastname: Ghosh