Intermolecular vibrations of 1-naphthol⋅NH3 and d3-1-naphthol⋅ND3 in the S and S1 states

Abstract

Hydrogen-bonded complexes of the photoacid 1-naphthol with NH3 and ND3 were investigated by resonant two-photon ionization, spectral hole burning, and fluorescence spectroscopies. Although the intermolecular vibrations are weak in both absorption and emission, with typical Franck–Condon factors <2% relative to the electronic origin, all six intermolecular modes were identified, namely the hydrogen bond stretch σ, the ammonia torsion τ, two in-plane wags β1 and β2, and two out-of-plane rocking motions ρ1 and ρ2. Several ammonia torsional excitations were observed, with spacings in good agreement with the S0- and S1 state effective torsional barriers derived by Humphrey and Pratt [J. Chem. Phys. 104, 8332 (1996)]. The β1, β2, and ρ2 vibrational excitations exhibit large (2–8 cm−1) torsional splittings, which indicate strong anharmonic coupling with the ammonia internal rotation. The observed Franck–Condon factors of the intermolecular stretching vibration imply a contraction of the O–H⋅⋅⋅N hydrogen bond by ≈0.01 Å upon S1←S0 excitation.

Femtosecond Pump‐Probe Measurements of Solvation by Hydrogen‐Bonding Interactions

“…These were the stretch vibration of the hydrogen bond, two in-plane wag vibrations, two out-of-plane rocking motions and the ammonia torsion motion. In their 2001 paper, Henseler et al [68] concluded that "the observed increase of the stretch frequency in the S 1 state reflects a higher curvature due to a strengthening of the hydrogen bond after electronic excitation" and that "the hydrogen-bond strength and the changes in curvature and well depth upon electronic excitation are correlated". Lahmani et al [70] have studied the electronic and vibrational spectra of jet-cooled hydrogen-bonding complexes of o-cyanophenol.…”

“…Humphrey and Pratt [65][66] concluded that the hydrogen bond between 1-naphthol and the NH 3 moiety contracts by 0.14 after the electronic excitation of 1-naphthol. Leutwyler and co-workers [67][68][69] conducted several comprehensive studies on the spectroscopy of hydrogen-bonding complexes of photoacids. In all systems studied, they observed the strengthening of the hydrogen bond after electronic excitation.…”

Torsional Barriers in Aromatic Molecular Clusters as Probe of the Electronic Properties of the Chromophore

“…[15] Furthermore, excited-state torsional bands were given in the above publication for the [d 3 ]1-naphthol(ND 3 ) 1 tautomer. Humphrey and Pratt [16] presented the rotationally resolved spectrum of the electronic origin of 1-naphthol(NH 3 ) 1 .…”

“…If the hole-burning spectrum shown in ref. [19] was analyzed at the high-frequency side of the origin band, [a] AE splitting, DB g , and D g constants from Humphrey et al [16] [b] Vibronic transitions from Henseler et al [15] [c] DF data from Henseler et al [15] [a] AE splitting, DB g , and D g constants from Plusquellic et al [18] [b] Vibronic transitions from Droz et al [17] [c] DF data from Droz et al [17] [a] Vibronic bands of phenol(NH 3 ) 1 from Schiefke et al [19] [b] Vibronic bands of phenol(ND 3 ) 1 from Jacoby. [20] the small intensity of the E bands in the hole-burning spectrum could easily be explained.…”

“…Here, W ð1Þ vs is the first-order perturbation coefficient for the state j v,si coming from the Van Vleck transformation and it is given by Equation (15).…”