Noncovalent Interactions in the Gas Phase: The Anisole–Phenol Complex

Abstract

The present paper reports on an integrated spectroscopic study of the anisole-phenol complex in a molecular beam environment. Combining REMPI and HR-LIF spectroscopy experimental data with density functional computations (TD-M05-2X/M05-2X//N07D) and first principle spectra simulations, it was possible to locate the band origin of the S(1) ← S(0) electronic transition and determine the equilibrium structure of the complex, both in the S(0) and S(1) electronic states. Experimental and computational evidence indicates that the observed band origin is due to an electronic transition localized on the phenol frame, while it was not possible to localize experimentally another band origin due to the electronic transition localized on the anisole molecule. The observed structure of the complex is stabilized by a hydrogen bond between the phenol, acting as a proton donor, and the anisole molecule, acting as an acceptor through the lone pairs of the oxygen atom. A secondary interaction involving the hydrogen atoms of the anisole methyl group and the π electron system of the phenol molecule stabilizes the complex in a nonplanar configuration. Additional insights about the landscapes of the potential energy surfaces governing the ground and first excited electronic states of the anisole-phenol complex, with the issuing implications on the system photodynamic, can be extracted from the combined experimental and computational studies.

Resonant Two-Photon Ionization Studies of Toluene with Anisole Cluster: A System with Competing Non-Covalent Interactions

“…Two isomers are characterised through a central interaction of the anisole methyl group to the aromatic ring system of toluene, while the third isomer leads to a side‐on interaction of the methyl group to the toluene. In contrast to calculations performed on other aromatic compounds, a π‐stacked structure is not found.…”

Effect of Noncovalent Interactions on Vibronic Transitions: An Experimental and Theoretical Study of the C2H⋅⋅⋅CO2 Complex

“…The reported examples of the effects of noncovalent interactions on electronic transitions are quite limited. On the theoretical side, very few examples of calculations of excited states of complexes involving more than four atoms have been reported . This kind of investigation is still in its infancy, mainly due to the extreme difficulty of managing the excited states at a level of accuracy as good as achieved for the ground states …”

Multi-spectroscopic and theoretical analyses on the diphenyl ether–tert-butyl alcohol complex in the electronic ground and electronically excited state

“…In a purely theoretical work, Zhao et al 22 predicted a red-shifted OH-stretching frequency in the S 1 compared to the S 0 state of the fluorenonemethanol complex, obtained by time-dependent density functional theory (TD-DFT) calculations. In a combined experimental and theoretical work, Pietraperzia et al 23 investigated the anisole-phenol complex in the S 0 and S 1 state. They recorded REMPI and HR-LIF spectra and were able to assign rotational transitions corresponding to the OH-O structure in the S 0 and S 1 states.…”