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Articles you may be interested inRotational analysis and tunnel splittings of the intermolecular vibrations of the phenol-water complex by high resolution UV spectroscopy J. Chem. Phys. 108, 4496 (1998); 10.1063/1.475861 Infrared spectroscopy of OH stretching vibrations of hydrogenbonded tropolone(H2O) n (n=1-3) and tropolone (CH3OH) n (n=1 and 2) clusters

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The properties of the three lowest singlet electronic states (ground, (1)L(b), and (1)L(a) states) of indole (C(8)H(7)N) have been calculated with second-order approximate coupled-cluster theory (CC2) within the resolution-of-the-identity approximation. Refined electronic energies at the CC2 optimized structures and transition dipole moments were calculated using a density functional theory multi-reference configuration-interaction (DFT/MRCI) approach. Structures, energies, and dipole moments are reported for all three states and compared to experimental values. From the optimized structures and calculated transition dipole moments, we predict that pure (1)L(b) bands will have positive signs for both the axis reorientation angle theta(T) and the angle theta of the transition dipole moment with respect to the inertial a axis. For (1)L(a) bands the signs of both angles will be reversed. Vibronically coupled bands can exhibit opposite signs for theta and theta(T). The absorption and emission spectra of indole are calculated based on the Franck-Condon Herzberg-Teller approximation using numerical transition dipole moment derivatives at the DFT/MRCI level of theory. Implications for the experimentally observed vibronic spectra are discussed. Predictions are made for rotationally resolved spectra of various rovibronic bands. A conical intersection, connecting the (1)L(b) and (1)L(a) states, which can be accessed to varying extents via different Herzberg-Teller active modes is found approximately 2000 cm(-1) above the (1)L(b) minimum.

The intermolecular vibrations of jet-cooled phenol(H2O)2-5 and phenol(D2O)2-5-d 1 were investigated in the S0 and S1 electronic states by using mass-selective UV spectral hole burning (SHB) and single vibronic level dispersed fluorescence (DF) spectroscopy. Phenol(H2O)2 shows broad bands with congested structure. We succeeded in obtaining its intermolecular vibrations via double-resonance spectroscopy. Previous studies of phenol(H2O)3 were completed. By employing soft two-color ionization and spectral hole burning, the vibronic spectra of phenol(H2O)4 and phenol(H2O)5 were unambiguously assigned according to cluster size and discriminated for possible isomers. An essentially complete picture of the vibronically active intermolecular vibrations was obtained. This was possible because SHB proves to be sensitive to the higher frequency intermolecular vibrations which tend to fast intramolecular S1 vibrational relaxation in the larger clusters and therefore are of low intensity or absent in the two-color ionization spectra. The experimental results are compared to normal mode calculations based on fully optimized cluster structures obtained from ab initio studies at the Hartree−Fock level. Phenol(H2O)2-4 exhibit cyclic structures of the water moiety, while in case of phenol(H2O)5 the cyclic and a bridged “double-donor” structure are of comparable energy. The 6n − 6 intermolecular vibrations of the cyclic clusters with n ≥ 3 monomers can be classified into three small amplitude mutual rotations of the phenyl ring and the oxygen moiety, 2n − 6 oxygen ring deformation vibrations, n intermolecular stretch vibrations, and 3n − 3 hindered rotations of the water molecules in the cluster. The “double-donor” clusters exhibit a strong coupling of some of these modes. Many of the intermolecular vibrations, especially the mutual ring motions and the stretch vibrations, are optically active and can be assigned in the S0 state by comparison with the calculated vibrational frequencies and deuteration shifts. The propensity rule helps to assign the corresponding vibrations in the S1 state.