Microwave Spectra and Structure of Ar–1,3-Difluorobenzene

Abstract

The microwave spectrum of the dimer Ar-1,3-difluorobenzene from 2 to 18 GHz is reported. The spectrum has been observed using a chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer that has recently been expanded to include the 2-6 GHz region of the electromagnetic spectrum. Details of this upgraded spectrometer are reported. Eighty-seven transitions were observed for the parent dimer spectrum, which was adequately fit to a semirigid rotational Hamiltonian consisting of A, B, and C as well as four quartic centrifugal distortion constants. Observations of C species in natural abundance were aided by utilizing smaller chirp ranges of 7-9 and 9-11 GHz for 1.9 million and 3.73 million averages, respectively. Assignment ofC isotopologues allowed for determination of the Kraitchman coordinates of the carbon atoms as well as inertial fits of the complex. The quantum-chemical structure predicts an Ar to monomer center of mass distance of 3.48 Å, compared with 3.564(1) Å determined from experimental structural analysis. This new study indicates that in fluorinated benzene-Ar dimers, when the fluorines are separated by more carbon atoms, the Ar-ring center distance decreases.

Rotational Spectrum and Molecular Structures of the Binary Aggregates of 1,1,1,3,3,3-Hexafluoro-2-propanol with Ne and Ar

“…Although CREST has been utilized for conformational searches of flexible organic molecules and hydrogen-bonded complexes, such as perillyl alcohol and dimers of tetrahydro-2-furoic acid, this code has rarely been used for conformational searches of rare gas···organic molecule van der Waals complexes. Many of the recent studies relied on potential energy scans along specific coordinates or using previous experience with similar systems to identify the possible structures. ,, In a recent study of the propylene oxide trimer, which is bound dominantly by van der Waals and induction interactions, CREST failed to generate the structural candidate of the most stable heterochiral trimer . It would be interesting to see how CREST performs with these very weakly bound systems involving rare gas atoms.…”

“…Many of the recent studies relied on potential energy scans along specific coordinates or using previous experience with similar systems to identify the possible structures. 13,23,32 In a recent study of the propylene oxide trimer, which is bound dominantly by van der Waals and induction interactions, CREST failed to generate the structural candidate of the most stable heterochiral trimer. 33 It would be interesting to see how CREST performs with these very weakly bound systems involving rare gas atoms.…”

The Conformational Landscape, Internal Rotation, and Structure of 1,3,5-Trisilapentane using Broadband Rotational Spectroscopy and Quantum Chemical Calculations

“…The rotational spectrum was then obtained in the 6–18 GHz spectral region using a chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer. This instrument has been detailed in the literature elsewhere. − The sample was introduced into the spectrometer at a backing gas pressure ∼1 atm above ambient (2 atm total) pressure from a pulsed supersonic nozzle (molecular beam). The chamber pressure, meanwhile, was held at 10 –6 Torr.…”

Theoretical Calculations, Microwave Spectroscopy, and Ring-Puckering Vibrations of 1,1-Dihalosilacyclopent-2-enes

“…The microwave measurements were carried out at the Missouri University of Science and Technology using a Chirped Pulse, Fourier Transform Microwave Spectrometer (CP-FTMW). The details of this spectrometer have been outlined previously. − The sample, originally a liquid, was made into a gas mixture by utilizing the vapor pressure of the molecule at room temperature. A gas tank was evacuated and attached to the sample, which then allowed the sample to vaporize.…”