•  
  •  
 

Georgia Journal of Science

Article Title

THE TORSIONAL OSCILLATION MODEL OF T-SHAPED CYANOACETYLENE CARBON DIOXIDE DIMER COMPLEX, HCCCN ··· CO2

Abstract

The rotational spectrum of T-shaped cyanoacetylene carbon dioxide van der Waals complex, HCCCN ... CO2, was measured using two Balle-Flygare Fourier transform microwave (FTMW) spectrometers between 1.4 GHz and 25 GHz. Only the even numbered Ka branches of spectrum were observed. The vanishing of odd numbered Ka transitions demonstrates a C2v symmetry due to the T-shaped alignment of complex subunits. The spectroscopic constants were fit by Pickett’s SPFIT/SPCAT programs: A0 = 11273(18) MHz, B0 = 764.088(21) MHz, C0 = 716.254(21) MHz, ΔJ = 0.50329(34) kHz, ΔJK = 0.120867(11) MHz, ΔK = -28.17(36) MHz, δJ = 61.3(21) Hz, δK = 44.25(95) kHz, ΦJ = 0.0053(12) Hz, ΦJK = 9.820(55) Hz, ΦKJ = -0.59325(72) kHz, ΦK = -2.3719(53) MHz, øJ = 0.0398(42) Hz, øJK = 6.9(9) Hz, and øK = -3.592(13) kHz. The 14N nuclear quadrupole coupling constants were χaa = -4.12753(38) MHz and χbb – χcc = 0.103(15) MHz. The small, yet negative inertia defect, Δ0 = -0.66(12) u∙Å2, illustrates an averaged planar geometry with non-negligible low frequency out-of-plane vibrations. In addition, both binding partners exhibit large-amplitude bending vibrations within their symmetric plane. The classical precession model cannot handle the intermolecular dynamics in this system. A new model was thus developed in present work for the structural analysis. According to our torsional oscillation model, HCCCN subtends a 10.(1)° angle with the a-axis and CO2 subtends a 5.4(5)° angle with the b-axis of complex. The effective van der Waals bond length is 3.0137(3) Å. The stretching force constant, ks = 3.9 N/m, and the stretching frequency, νs = 53 cm-1, for the van der Waals bond were calculated using the pseudo-diatomic model. The MP2 and DFT calculations were performed to predict the complex structures, rotational constants, and the quadrupole coupling strengths. The results are compared to the experimental results.

This document is currently not available here.

Share

COinS