The rotational spectrum, geometry, and intermolecular force constant of the heterodimer of hydrogen cyanide and fluoroform

Abstract

The ground-state rotational spectra of six isotopic species of an intermolecular complex formed by hydrogen cyanide and fluoroform have been measured using the pulsed-nozzle, Fourier-transform microwave technique. The rotational constant B0, the centrifugal distortion constants DJ,DJK,HJ, HJK, and HKJ, and, where appropriate, the nuclear quadrupole coupling constants χ(14N) and χ(D) have been determined for each of the species HC14N⋅⋅⋅HCF3, DC14N⋅⋅⋅HCF3, HC14⋅⋅⋅DCF3, HC15N⋅⋅⋅HCF3, HC15N⋅⋅⋅DCF3, and DC15N⋅⋅⋅HCF3. For HC14N⋅⋅⋅HCF3 the values are as follows: B0=1151.2991(4) MHz, DJ=1.91(1) kHz, DJK=282.75(6) kHz, HJ=−0.1(1) Hz, HJK=44.3(5) Hz, HKJ=53(5) Hz, and χ(14N)=3.948(8) MHz. The form of the spectra and magnitudes of the rotational constants allow the conclusion that the geometry of the complex is of C3V symmetry with the nuclei in the order HCN⋅⋅⋅HCF3 and lead to r(N⋅⋅⋅C)=3.489(2) Å for HCF3 species but 3.483(1) Å for DCF3 species. The intermolecular stretching force constant determined from DJ is kσ=3.52 N m−1.