Vibrational-Energy Redistribution and Vibronic Coupling in 1-Naphthol·Water Complexes

Abstract

Resonant two-photon ionization (R2PI) and fluorescence spectra of the 1-naphthol·H2O and 1-naphthol-d 1·D2O cluster are reported and interpreted with emphasis on intracomplex vibrational energy redistribution (IVR) and vibronic coupling. The analysis included an ab initio normal-coordinate calculation of both complexes at the 6-31G (d,p) level. In S1 ← S0 R2PI spectra, the intermolecular modes were found to be very weak; only one such S1 vibration was observed at 57 cm-1 (54 cm-1 for 1-naphthol-OD·D2O). At excitations less than 400 cm-1 above the S1← S0 origin, the fluorescence spectra retain a simple 1-naphthol-like pattern. At higher excess energies, the fluorescence exhibits complex structure due to emission from both relaxed and unrelaxed S1 vibrational states, showing efficient coupling through the hydrogen bond. This restricted IVR behavior changes to dissipative IVR at about 834 cm-1 above the S1 ← S0 origin. Exceptions to general IVR are observed. The S1 + 403 cm-1 level is a restricted IVR case, while the nearby S1 + 400 cm-1 level undergoes nearly dissipative IVR. On the other hand, a nearly “frozen” mode is observed at 553 cm-1 above the S1← S0 origin. By use of the ab initio vibrational analysis and lowest-order anharmonic coupling, the IVR-active vibrational “bath” states can be predicted, enabling tentative assignment of much of the relaxed fluorescence structure. Ion-dip spectroscopy shows that IVR in the electronic ground state may have a higher onset threshold than in the S1 by ≥130 cm-1. Exciting one quantum of the 57 cm-1 intermolecular mode results in a decreased S0 IVR threshold. The strong vibronic S1−S2 coupling earlier observed for vibrations at S1 + 410 and S1 + 414 cm-1 in free 1-naphthol was found to be partially inhibited in 1-naphthol·H2O but still significant in 1-naphthol-OD·D2O. This is attributed to harmonic mode mixing. In contrast, vibronic coupling becomes active in the S1 + 292 cm-1 level of 1-naphthol·H2O.

Mass-Analyzed Threshold Ionization of the trans-1-Naphthol−Water Complex: Assignment of Vibrational Modes, Ionization Energy, and Binding Energy

“…The first transition (56.2 cm -1 ) is assigned to the first quantum of an intermolecular in-plane bending vibration ( ip ) 1 0 , the second (59.9 cm -1 ) is the second quantum of an out-of-plane bending vibration ( oop ) 2 0 . 13 The in-plane bending vibration is also observed as a progression of the 34 1 0 transition (34 1 0 ( ip ) 1 0 ) partly overlapping with the 33 1 0 transition. We found no evidence for further intermolecular vibrations in the S 1 rS 0 spectrum.…”

Is there an Excited State Proton Transfer in phenol (or 1 -naphthol)-ammonia clusters? Hydrogen Detachment and Transfer to Solvent: A key for non-radiative processes in clusters

“…Numerous studies have been performed along this line, to characterize the proton transfer reactions in neutral and ionic clusters. ESPT has been thought to be observed in two model systems: 1-naphthol±ammonia (Cheshnovsky and Leutwyler 1985, Kim et al 1991, Knochenmuss et al 1993, Knochenmuss and Smith 1994, Yi and Scheiner 1996, Kelley and Bernstein 1999, Knochenmuss 1999a,b, Knochenmuss et al 1999, DedonderLardeux et al 2001, Knochenmuss et al 2001, and phenol±ammonia , Steadman and Syage 1990, Syage and Steadman 1991, Steadman and Syage 1992, Hineman et al 1993, Syage 1993a,b, Martrenchard-Barr a et al 1999, Pino et al 1999, Kim et al 2000, Pino et al 2000.…”

Intermolecular bonding and vibrations of phenol⋅oxirane

“…4,[18][19][20][21][22][23][24] On the other hand, density functional calculations are becoming popular because of the potential they offer to obtain the correlation energy with lower computational effort. [30][31][32][33][34] Several applications to hydrogenbonded complexes have already been made, and the results indicate that large basis sets including diffuse functions are necessary to obtain reliable results.…”

“…[15][16][17] This has in some cases been complemented by ab initio theoretical investigations. 4,[6][7][8][18][19][20][21][22][23][24] Hydrogen bonded complexes of phenol have been studied in molecular beams using a number of different spectroscopic techniques, which address either or both the S 0 electronic ground-state and the S 1 excited state. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]25,26 One of the simplest molecules that acts exclusively as a hydrogen bond acceptor is the C 2v symmetric cyclic ether oxirane ͑ethylene oxide͒.…”