Temperature and Size Dependence of Characteristic Hydrogen-Bonded Network Structures with Ion Core Switching in Protonated (Methanol)_6–10–(Water)₁ Mixed Clusters: A Revisit

Abstract

Hydrogen-bonded network structures and preferential ion core in the protonated methanol-water mixed clusters, H(methanol)-(water) (n = 6-10), were explored by a combination of infrared spectroscopy and theoretical calculations. Infrared spectra of the OH stretch region of the clusters were measured at the two different temperature ranges by using Ar-tagging. Stable isomer structures of the clusters were searched by the multiscale modeling approach and temperature dependent infrared spectra were simulated based on the statistical populations of the isomers. The combined experimental and theoretical studies revealed that the characteristic multiring structures begin to form at n = 7 under the low temperature condition and they are preferential at the wide temperature range in n ≥ 8. It was also demonstrated that the preferential ion core type changes from methanol (MeOH) to water (HO) with increasing cluster size. In n ≤ 8, the observed infrared spectral features partly depend on the monitoring vibrational predissociation channel, and weak correlations between the hydrogen-bonded network structure and preferential dissociation channels were suggested. However, the ion core type does not necessarily correlate to the preferential dissociation channel. This implies that large rearrangement of the hydrogen-bonded network structure occurs prior to the dissociation.

Hydrogen bond network structures of protonated short-chain alcohol clusters

“…A similar H-bond network structure, called a ''multi-ring'' or ''inclusion'' structure, can be constructed for H 3 O + (MeOH) n , and its actual formation was recently confirmed by IR spectroscopy and theoretical computations of H + (MeOH) n (H 2 O) 1 . 153,154 For methanolated ions, H-bonded network structures in the 2nd and 3rd shells have not yet been closely examined, except for some trials of theoretical modeling. 112,113,115 Experimental confirmation of H-bond networks in large methanolated ions is future work of great interest.…”

Anharmonic Coupling Revealed by the Vibrational Spectra of Solvated Protonated Methanol: Fermi Resonance, Combination Bands, and Isotope Effect

“…The neutral methanol molecule has one OH bond, and thus it can play as a single proton donor, and/or a single/double proton acceptor in hydrogen bond (H bond) networks through its lone pair electrons on oxygen. − The protonated methanol, by contrast, has two OH bonds and can be a single/double proton donor. As a result, it has been shown to form more various types of H bond networks in the clusters either composed of neat methanol − or a mixture with other species, e.g., water. − Through the cooperation between experimental measurements and computational efforts, a variety of H bond networks such as linear, branched, cyclic, and cage-like forms have been confirmed. − …”

Correlation of the Charge Resonance Interaction with Cluster Conformations Probed by Electronic Spectroscopy of Dimer Radical Cations of CO2 and CS2 in a Cryogenic Ion Trap

“…One of the gold standards for producing molecular cluster ions is by combining the generation of neutral clusters through supersonic expansion with the ionization by crossed electron beams, a method pioneered by Märk and co-workers, Lineberger and co-workers, and others. ,, The ionization step of this technique includes cluster heating via electron impact and subsequent cooling via evaporation of excess molecules, which are balanced to eventually achieve a typical average internal temperature of ∼100 K for the cluster ions. − Owing to the relatively weak intracluster interactions compared to the typical intramolecular chemical bonds, the clusters at this temperature range frequently exhibit high fluxionalityfacile isomerization between energetically close conformers. − Because the intracluster interactions are generally strongly correlated with the cluster conformations, ,,, regulation of the internal temperature of the clusters, particularly under cryogenic conditions, remains a significantly challenging aspect that has not been adequately addressed in the extensive research conducted over the decades. Indeed, a recent spectroscopic study utilizing superfluid helium nanodroplets at sub-Kelvin temperatures successfully identified the hemibonded isomer of [(H 2 O) 2 ] +• formed through CR interactions .…”