Hole‐Burning Spectra of m‐Fluorophenol/Ammonia (1:3) Clusters and Their Excited State Hydrogen Transfer Dynamics

Abstract

Hole-burning spectra of m-fluorophenol/ammonia (1:3) clusters are measured by four-color UV-near IR-UV-UV hole-burning spectroscopy. Cis and trans isomers of the cluster are clearly distinguished in the (1:3) cluster. Picosecond time evolutions of the excited state hydrogen transfer (ESHT) reaction in the (1:3) clusters are measured by the ion depletion due to 3p-3s Rydberg transition of reaction products ⋅NH(4)(NH(3))(2) lying in the near infrared region. From the wavelength dependence of the time evolution, we have concluded 1) the initial formation of a metastable ⋅NH(4)-NH(3)-NH(3) radical and 2) successive isomerization to the most stable NH(3)-⋅NH(4) -NH(3) radical in both cis and trans isomers. The reaction lifetimes of ESHT are determined by the rate equation analysis as 32.4 and 31.8 ps for the cis and trans isomer, respectively, and the isomerization and its back-reaction lifetime of both isomers are determined to be 3.3 ps and 11.2 ps. The almost same reaction rates are consistent with the similarity of the hydrogen bond networks in both clusters.

Hydrogen bond dynamics in the excited states: Photodissociation of phenol in clusters

“…The latter radical is analogous to the hydronium radical found in the photochemistry of aqueous systems 34,53 or NH 4 radical observed during the PhOHÁ Á ÁNH 3 photodissociation. 32,54 The Ph-OH 2 radical is stable with respect to the O-H or O-Ph dissociation in the D 1 state (corresponding to the S 1 state of the phenol dimer after the excited state hydrogen transfer) but the conical intersection with the ground state D 0 (corresponding to the S 0 state of the phenol dimer) is within reach (as can be seen also in Fig. 4(b)).…”

Revealing the role of excited state proton transfer (ESPT) in excited state hydrogen transfer (ESHT): systematic study in phenol–(NH3)n clusters

“…The H transfer mechanism has been studied in several PhOH derivatives. 65 Most of the molecules have been studied in their complexes with a single solvent molecule such as ammonia and amines. The first goal was to demonstrate that ESHT occurs in various aromatics, and the mechanisms were discussed in terms of tunneling.…”

Early-Stage Dynamics in Coupled Proton–Electron Transfer from the π–π* State of Phenol to Solvent Ammonia Clusters: A Nonadiabatic Electron Dynamics Study

“…We here report our nonadiabatic electron wavepacket study on the excited-state reaction in phenol that is hydrogen-bonded with ammonia clusters Ph * OH ··· false( NH 3 false) n → PhO • ··· false[ normalH false( NH 3 false) n false] * • with n ≤ 5. This reaction is now widely recognized as a typical reaction of excited-state hydrogen atom transfer. − It has been established that the initially promoted π–π*-state conical-intersects with π–σ* state, which pumps the hydrogen atom from phenol to the ammonia cluster. An important and difficult aspect of this reaction is that the relevant low-lying electronic states are highly quasi-degenerate due to the Rydberg-like diffused states on the ammonia cluster.…”