Non-covalent interactions in anisole–(CO₂)_n (n = 1, 2) complexes

Abstract

Non-covalent interactions are ubiquitous and represent a very important binding motif. The direct experimental measurement of binding energies in complexes has been elusive for a long time despite its importance, for instance, for understanding and predicting the structure of bio-macromolecules. Here, we report a combined experimental and computational analysis on the 1 : 1 and 1 : 2 clusters formed by anisole (methoxybenzene) and carbon dioxide molecules. We have obtained a detailed description of the interaction between CO 2 and anisole. This system represents quite a challenging test for the presently available experimental and theoretical methods for the characterization of weakly bound molecular complexes. The results, evaluated in the framework of previous studies on anisole clusters, show a very good agreement between experimental and theoretical data. A comparison of the experimental and computational data enabled the binding energy values of the 1 : 1 and 1 : 2 clusters to be determined in the ground electronic state of the neutral and cation complex and in the first excited singlet state of the neutral complex. In addition, it was possible to adduce the presence of different 1 : 1 + conformers, prepared by direct ionization of the 1 : 1 complex or by dissociative ionization of the 1 : 2 complex.

Computational study of the interaction of the psychoactive amphetamine with 1,2-indanedione and 1,8-diazafluoren-9-one as fingerprinting reagents

“…The Grimme's D3 dispersion correction was shown to increase the accuracy of non-covalent interactions. 27,[38][39][40][41] The optimised structures were thereaer conrmed to be real minima by performing frequency calculations using the same method. All structures showed positive force constants for all the normal modes of vibration.…”

C–H/π and C–H–O Interactions in Concert: A Study of the Anisole–Methane Complex using Resonant Ionization and Velocity Mapped Ion Imaging

“…(2,16,30−36) Isolated clusters can be readily prepared experimentally through use of jet-cooled supersonic expansions (molecular beams), (5,16,37−39) with electronic or infrared spectroscopy used to classify spectral changes of the chromophore upon cluster formation. The advent of velocity mapped ion imaging (VMI) has provided another tool for investigating the binding energies of clusters,(40−44) which the Anisole is a prototypical aromatic chromophore, (52) readily detected via R2PI methods, and relevant for studying different intermolecular interactions, as evident by the variety of reported studies on the formation and characterization of molecular complexes of anisole with simple systems including CO2, (33) NH3, (53) H2O, (31) and Ar. (54) In addition, the anisole dimer has been extensively studied.…”

“…Many prior studies of weakly bound clusters have utilized a reference chromophore, often consisting of an aromatic moiety that can be spectroscopically detected via fluorescence or resonant ionization methods, bound to different species (e.g., rare gas, diatomic, or small polyatomic molecules) to probe the structure and strength of the interaction mechanism. ,,− Isolated clusters can be readily prepared experimentally through use of jet-cooled supersonic expansions (molecular beams), ,,− with electronic or infrared spectroscopy used to classify spectral changes of the chromophore upon cluster formation. The advent of velocity mapped ion imaging (VMI) has provided another tool for investigating the binding energies of clusters, − which the Reisler group has exploited to measure the binding energies of a variety of model hydrogen-bonded complexes. − In the present article, we utilize anisole as a chromophore and employ resonant 2-photon ionization (R2PI) and VMI methods to probe the anisole–methane complex.…”

“…Anisole is a prototypical aromatic chromophore, readily detected via R2PI methods, and relevant for studying different intermolecular interactions, as evident by the variety of reported studies on the formation and characterization of molecular complexes of anisole with simple systems including CO 2 , NH 3 , H 2 O, and Ar . In addition, the anisole dimer has been extensively studied. ,, With two main primary sites available as proton acceptors, it is noteworthy that the anisole–H 2 O 1:1 complex exhibits a hydrogen bond with the oxygen lone pair, while the anisole–NH 3 1:1 complex is of a π-type.…”