Anomalous band shifts in the 14 μm infrared absorption spectra of rare gas–BF3 complexes

Abstract

The 14 μm bands of BF3-CO complexes: Isotopedependent chaotic fine structure J. Chem. Phys. 98, 3612 (1993); 10.1063/1.464038 Freejet infrared absorption spectroscopy of rare gas-1 1BF3 complexes in the 7 μm region High resolution infrared absorption spectra of rare gas (Rg)-BF3 van del' Waals complexes are studied in the 14 f.1m region near the 1'2 band of BF3 monomer. Spectroscopic constants are determined for the 2oNe_llBF 3' Ar_JO,IlBFJ' 82-84.86Kr_IIBF3' and 84Kr-1oBF3 complexes. The observed redshifts from the monomer band origin correlate linearly with the rare gas polarizabilities. These shifts are about three times as large as those measured previously near the monomer v.) band. This mode dependence of the shifts cannot be reproduced in a consistent manner with the instantaneous vibrational dipole-induced dipole interaction model, and indicates much greater enhancement of bonding energy by the excitation of "'2 vibration. The band shifts are discussed on the basis of electrostatic interaction behveen rare gas atom and point charges on BF 3 . The anomalous band shifts for the V2 band are successfully accounted for by the interaction of vibrational dipole moment with the static induced dipole moment on the rare gas atom, which is parallel to the direction of vibrational motion. The isotope shifts observed for the Kr-BF 3 complexes and the band shifts due to the modification of force field by vdW bonding are discussed with a linear triatomic molecular model.

Van der Waals Complexes between Boron Trifluoride and Carbon Monoxide in Liquefied Argon: An Infrared Study

“…For both ν 2 and ν 3 the vibrational dipole moment is for the larger part determined by the motion of the boron atom . The data in Table indicate that the modes in 10 BF 3 show a slightly bigger solvent shift than those in 11 BF 3 .…”

“…Unfortunately, no studies of this complex have been published. However, high-resolution infrared spectra of BF 3 ·Ar have been investigated , in the regions of ν 2 and ν 3 , and we will interpret our solution frequencies in terms of these data.…”

“…In the gas phase, ν 3 ( 11 B) shifts by −1.7609 cm -1 from BF 3 to BF 3 ·Ar, while the shifts for ν 2 ( 10 B) and ν 2 ( 11 B) are 18 −6.0022 and −5.7099 cm -1 , respectively. In the inductive model of Lee et al, this considerable mode specificity is explained by the orientation of the vibrational dipole gradient relative to the static dipole moment induced by the partial charges on B and F atoms in the argon atom. For ν 3 , the gradient is oriented perpendicular to the static induced dipole moment, while for ν 2 it is parallel with it, allowing the v = 1 state of ν 2 to be stabilized much more than the corresponding state of ν 3 , leading to the observed difference in the frequency shifts.…”

“…For both ν 2 and ν 3 the vibrational dipole moment is for the larger part determined by the motion of the boron atom .…”

Van der Waals Complexes between Unsaturated Hydrocarbons and Boron Trifluoride: An Infrared and ab Initio Study of Ethene·BF3 and Propene·BF3

“…As a result, BF 3 readily forms stable adducts with electron donors, particularly with nitrogen and oxygen bases. − These adducts have been studied using a variety of techniques. − Under cryogenic conditions also a number of weakly bound complexes have been studied to date. For instance, molecular beam high-resolution infrared spectra of the adduct of BF 3 with Ne, Ar, Kr, N 2 , and CO have been observed by Takami and co-workers, − and similar complexes involving HCN and HCCCN were described by Kerstel et al . Also, the molecular beam microwave spectra of BF 3 complexes with a variety of Lewis bases have been reported, − and the complexes with N 2 , CO, and H 2 O, as well as the BF 3 dimer, have been identified in matrix isolation infrared studies. − …”