INTERMOLECULAR FORCES IN ARGON VAN-DER-WAALS COMPLEXES - ROTATIONAL SPECTRUM AND AB-INITIO INVESTIGATION OF AR-OXAZOLE

Citation
E. Kraka et al., INTERMOLECULAR FORCES IN ARGON VAN-DER-WAALS COMPLEXES - ROTATIONAL SPECTRUM AND AB-INITIO INVESTIGATION OF AR-OXAZOLE, Journal of physical chemistry, 99(33), 1995, pp. 12466-12477
Citations number
67
Categorie Soggetti
Chemistry Physical
ISSN journal
00223654
Volume
99
Issue
33
Year of publication
1995
Pages
12466 - 12477
Database
ISI
SICI code
0022-3654(1995)99:33<12466:IFIAVC>2.0.ZU;2-A
Abstract
The rotational spectrum of the oxazole-argon complex has been experime ntally studied in the microwave region between 3 and 21 GHz using a pu lsed molecular beam Fourier transform microwave spectrometer. The rota tional constants were found to be A = 5012.894 86(14) MHz, B = 1398.42 8 151(32) MHz, and C = 1388.952 841(31) MHz. The centrifugal distortio n constants are D-J' = 5.524 11(28) KHz, D-JK' = 37.1990-(30) kHz, D-K ' = -35.922(28) kHz, delta(J)' = 0.026 26(21) kHz, and R'(6) = -0.000 49(19) kHz. The diagonal elements of the nitrogen quadrupole coupling tenser were determined to be chi(aa) = 2.3032(6) MHz, chi(bb) = -4.052 6(8) MHz, and chi(cc) = 1.7494(4) MHz. With the help of supermolecular Moller-Plesset perturbation theory at second (MP2) and fourth order ( MP4(SDTQ)) using a (14s10p2d1f)[7s4p2d1f] basis set for argon, a 6-31G (+sd+sp) basis for oxazole, and basis set superposition corrections, s tability (MP2, 316; MP4, 304 cm(-1)), equilibrium geometry, charge dis tribution, and other properties of the complex were determined. Argon adopts a position above the ring plane (Ar-ring distance: r(0), 3.46; MP2, 3.64; MP4, 3.58 Angstrom) clearly shifted from the centrum of the ring in the direction of the oxygen atom. The complex is predominantl y stabilized by dispersion interactions, while the position of the arg on atom is determined by exchange repulsion forces that direct Ar towa rd the O atom. A new way of analyzing van der Waals complexes and pred icting structural and other complex properties is presented. Investiga tion of Ar-oxazole, Ar-benzene, and Ar-CO reveals that there is no cha rge transfer between the complex partners, contrary to previous claims made in the literature.