Competition between van der Waals and hydrogen bonding interactions: structure of the trans-1-naphthol/N(2) cluster.
The excitation energy in the multiphoton ionization spectrum of the trans-1-naphthol/N(2) cluster shows only a small red shift with respect to isolated naphthol, indicating a van der Waals pi-bound structure rather than a hydrogen-bonded one. To confirm this interpretation, high-level electronic structure calculations were performed for several pi- and hydrogen-bonded isomers of this cluster. The calculations were carried out at the second order Møller-Plesset (MP2) level of perturbation theory with the family of correlation consistent basis sets up to quintuple-zeta quality including corrections for the basis set superposition error and extrapolation to the MP2 complete basis set (CBS) limit. We report the optimal geometries, vibrational frequencies, and binding energies (D(e)), also corrected for harmonic zero-point energies (D(0)), for three energetically low-lying isomers. In all calculations the lowest energy structure was found to be an isomer with the N(2) molecule bound to the pi-system of the naphthol ring carrying the OH group. In the CBS limit its dissociation energy was computed to be D(0) = 2.67 kcal/mol (934 cm(-1)) as compared to D(0) = 1.28 kcal/mol (448 cm(-1)) for the H-bound structure. The electronic structure calculations therefore confirm the assignment of the experimental electronic spectrum corresponding to a van der Waals pi-bound structure. The energetic stabilization of the pi-bound isomer with respect to the hydrogen-bonded one is rather unexpected when compared with previous findings in related systems, in particular phenol/N(2).
Xantheas
Sotiris S
SS
Pacific Northwest National Laboratory, 906 Battelle Boulevard, P. O. Box 999, MS K1-83, Richland, Washington 99352, USA. sotiris.xantheas@pnl.gov
Roth
Wolfgang
W
Fischer
Ingo
I
D003198:Computer Simulation; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008956:Models, Chemical; D009284:Naphthols / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D013237:Stereoisomerism
D009284:Naphthols; C029350:1-naphthol; D009584:Nitrogen