Microwave Spectroscopic and Atoms in Molecules Theoretical Investigations on the Ar⋅⋅⋅Propargyl Alcohol Complex: Ar⋅⋅⋅HO, Ar⋅⋅⋅π, and Ar⋅⋅⋅C Interactions

Abstract

The structure of the Ar···propargyl alcohol (Ar···PA) complex is determined from the rotational spectra of the parent complex and its two deuterated isotopologues, namely Ar···PA-D(OD) and Ar···PA-D(CD). The spectra confirm a geometry in which PA exists in the gauche form with Ar located in between -OH and -C≡C-H groups. All a, b and c types of transitions show small splitting due to some large-amplitude motion dominated by C-OH torsion, as in the monomer. Splittings in a- and b-type transitions are of the order of a few kilohertz, whereas splitting in the c-type transitions is relatively larger (0.9-2.6 MHz) and decreases in the order Ar···PA>Ar···PA-D(CD)>Ar···PA-D(OD). The assignments are well supported by ab initio calculations. Atoms in molecules (AIM) and electrostatic potential calculations are used to explore the nature of the interactions in this complex. AIM calculations not only reveal the expected O-H···Ar and π···Ar interactions in the Ar···gauche-PA complex, but also novel C···Ar (of CH2OH group) and O-H···Ar interactions in the Ar···trans-PA complex. Similar interactions are also present in the Ar···methanol complex.

Does a hydrogen bonded complex with dual contacts show synergism? A matrix isolation infrared and ab-initio study of propargyl alcohol–water complex

“…There have been previous experimental microwave [6,10] and infrared (IR) studies on PA [11]. The microwave spectrum of PA has confirmed the occurrence of only the g-PA [6,7].…”

“…The microwave spectrum of PA has confirmed the occurrence of only the g-PA [6,7]. Similarly, for propargyl thiol (C 3 H 4 S) [12][13][14][15] and propargyl selenol (C 3 H 4 Se) [16], only the g-PA conformer has been observed.…”

“…Arunan and group have reported the pure rotational spectra of Ar$$$PA complex [6], which was the first study on any weakly bound complex of PA. In this work, we have explored the 1:1 hydrogen bonded complexes of PA-H 2 O, using matrix isolation infrared spectroscopy and ab initio computations.…”

“…The conformations of PA arise from the internal rotation of the CeOH group in PA, which results in two conformations: the gauche (g-PA) and the trans (t-PA) form [6]. Calculations at the CCSD(T)-F12/VDZ-F12 level of theory [7] indicated the g-PA to be the lower energy conformer, with the higher energy trans structure (t-PA) being about 6.7 kJ/mol above g-PA. Hirota proposed that the intramolecular hydrogen bond between the eOH group and p electrons, was the reason for the g-PA being the ground state conformer [8].…”

Rotational spectra of propargyl alcohol dimer: A dimer bound with three different types of hydrogen bonds

“…[15][16][17][18] The ab initio calculations predict two conformers for the PA molecule: trans conformer (t-PA) and gauche conformer (g-PA), with the later being more stable than the former by about 350 cm −1 . 19 Rotational spectroscopic studies on PA monomer confirm the presence of only the gauche conformer and the trans-conformer is hitherto "experimentally unknown." [16][17][18] We recently reported the pure rotational spectra of Ar···PA complex.…”