Excited state hydrogen transfer in fluorophenol·ammonia clusters studied by two-color REMPI spectroscopy

Abstract

Two-color (1 + 1') REMPI mass spectra of o-, m- and p-fluorophenol.ammonia (1 ration) clusters were measured with a long delay time between excitation and ionization lasers. The appearance of NH(4)(NH(3))(n-1)(+) with 100 ns delay after exciting the S(1) state is a strong indication of generation of long-lived species via S(1). In analogy with the phenol.ammonia clusters, we conclude that an excited state hydrogen transfer reaction occurs in o-, m- and p-fluorophenol.ammonia clusters. The S(1)-S(0) transition of o-, m- and p-fluorophenol.ammonia (1 : 1) clusters were measured by the (1 + 1') REMPI spectra, while larger (1 ration) cluster (n = 2-4) were observed by monitoring the long-lived NH(4)(NH(3))(n-1) clusters action spectra. The vibronic structures of m- and p-fluorophenol.ammonia clusters are assigned based on vibrational calculations in S(0). The o-fluorophenol.ammonia (1 : 1) cluster shows an anharmonic progression that is analyzed by a one-dimensional internal rotational motion of the ammonia molecule. The interaction between the ammonia molecule and the fluorine atom, and its change upon electronic excitation are suggested. The broad action spectra observed for the o-fluorophenol.ammonia (1 : n) cluster (n>== 2) suggest the excited state hydrogen transfer is faster than in m- and p-fluorophenol.ammonia clusters. The different reaction rates between o-, m- and p-fluorophenol.ammonia clusters are found from comparison between the REMPI and action spectra.

Effects of Amino Substitution on the Excited State Hydrogen Transfer in Phenol: A TDDFT Study

“…It is interesting to note that Fujii's group has carried out the electronic spectroscopic study of fluorophenol·ammonia clusters to estimate that the ESHT reaction becomes faster in the order of m-, p-, and o-fluorophenol. 8 Substitution by halogen has an electron-withdrawing effect, while an amino group is a typical electron-donating one. It will be interesting to investigate the effect of an electron withdrawing group, such as a nitro group, in the ESHT reaction using an electronic structure calculation method.…”

“…The ESHT reaction is contrary to the traditional view that this cluster system will undergo an excited state proton transfer (ESPT) reaction as the pKa of this weak acid is lowered in the electronically excited state. 3 However, the ESHT reaction has been computationally predicted and experimentally confirmed in many systems including phenol, [4][5][6][7] halogenated phenols, 8,9 methylphenol, 10 thiophenol, [11][12][13] pyrrole, 14 indole, 15 and 3-methyl-indole. 16 The ESHT reaction of phenol is driven by a πσ* state that is repulsive along the O-H bond.…”

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

“…that reported in previous work. [45] From the analogy to m-FPhOH monomer, the group of bands around 35 900 cm…”

Ultrafast dynamics of o-fluorophenol studied with femtosecond time-resolved photoelectron and photoion spectroscopy

“…Discussions about electronic states of o-fluorophenol are numerous. Examples of such studies include the structural information on the S 0 and S 1 states using hole burning and high resolution ultraviolet spectroscopy [3], excited state hydrogen transfer studied by two-color resonance enhanced multiphoton ionization (REMPI) spectroscopy [4], the observation of the vibrationally resolved cation spectra by mass analyzed threshold ionization spectroscopy [5], nonresonant ionization detected by infrared spectroscopy [6], and vibrational spectra studied by Fourier transforminfrared (FT-IR) and FT-Raman spectroscopy [7,8]. All of these studies rely on the timescale of nanosecond (ns).…”