Structure of 1-Naphthol/Alcohol Clusters Studied by IR Dip Spectroscopy and ab Initio Molecular Orbital Calculations

The structures of 1-naphthol/alcohol clusters, 1-NpOH(ROH) n ( n = 1−3; ROH = MeOH, EtOH, and t -BuOH), have been investigated by resonant two-photon ionization (R2PI) spectroscopy and ion-detected IR dip spectroscopy. On the basis of the calculated spectra obtained by ab initio MO calculations, the spectra of 1-NpOH(MeOH) n was analyzed. The analysis elucidated that 1-NpOH(MeOH) 2,3 was a ring structure. From a similarity of the spectral pattern, the structures of 1-NpOH(EtOH) n and 1-NpOH( t -BuOH) n were also determined to be a ring conformation. From a frequency shift of the hydrogen-bonded OH stretching vibration, the hydrogen bonding is weakened by a steric hindrance due to an alkyl group of ROH. The difference in the solvation mechanism between 1-NpOH(MeOH) n and 1-NpOH(H 2 O) n is discussed.