THE TORSIONAL OSCILLATION MODEL OF T-SHAPED CYANOACETYLENE CARBON DIOXIDE DIMER COMPLEX, HCCCN ··· CO2
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.
Li*, Bingbing and Kang, Lu
"THE TORSIONAL OSCILLATION MODEL OF T-SHAPED CYANOACETYLENE CARBON DIOXIDE DIMER COMPLEX, HCCCN ··· CO2,"
Georgia Journal of Science, Vol. 76, No. 1, Article 36.
Available at: https://digitalcommons.gaacademy.org/gjs/vol76/iss1/36