Spectroscopy, lifetime, and charge-displacement of the methanol-noble gas complexes: An integrated experimental-theoretical investigation

An integrated experimental-theoretical investigation was employed to determine rovibrational energies, spectroscopic constants, lifetime as a function of temperature in gas phase complexes of methanol with noble gas (Ng=He, Ne, Ar, Kr, Xe, and Rn). Beside that, a parallel effort has been addressed to theoretically characterize the nature of intermolecular interactions determining the dissociation energy and equilibrium distance of the formed adducts. Dynamics and lifetime results reveal that, except for the CH3OH-He aggregate, all other methanol-Ng compounds are sufficiently stable under thermal conditions. Their lifetimes are larger than 1 ps for the temperature of the bulk in the range between 200 and 500 K. In addition, the current lifetime results suggest that the aggregates formed by methanol and Ng are globally more stable than corresponding complexes formed by water with Ng. From the point of view of the CCSD(T)/aug-cc-pVTZ level calculation, in all compounds, the electron densities of Ng partners are weakly polarized in the presence of CH3OH molecule. The charge-displacement curves and NBO analysis indicate that the charge transfer from Ng to methanol molecule, in general, plays a minor role, being appreciable only in the aggregate involving Ar. Finally, it was verified from the SAPT2 + (CCD)-delta MP2/aug-cc-pVTZ calculations and NCI analysis that the dispersion is the essential long-range attractive contribution to the interaction energy for all studied complexes. This feature strongly suggests that these compounds are held bonded substantially by van der Waals forces. Then non-covalent intermolecular bonds are effectively formed in the gas phase, which is disturbed by small stabilizing charge-transfer contributions. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

An integrated experimental-theoretical investigation was conducted to study gas phase complexes of methanol with noble gases, determining their rovibrational energies, spectroscopic constants, and lifetime as a function of temperature. The results show that the methanol-noble gas compounds are generally stable under thermal conditions, with lifetimes exceeding 1 ps in the temperature range of 200 to 500 K. The dispersion force is identified as the essential long-range attractive contribution to the interaction energy, indicating that these compounds are mainly bonded by van der Waals forces in the gas phase.