Rotational spectrum and structure of the T-shaped cyanoacetylene carbon dioxide complex, HCCCN⋯CO2

Lu Kang, Philip Davis, Ian Dorell, Kexin Li, Onur Oncer, Lucy Wang, Stewart E. Novick, Stephen G. Kukolich

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


The rotational spectrum of the T-shaped cyanoacetylene carbon dioxide dimer, HCCCN⋯CO2, was measured using two Balle-Flygare Fourier transform microwave (FTMW) spectrometers between 1.4 GHz and 25 GHz. Only the Ka = 0, 2, 4 branches of spectrum from J′ = 1 ← 0 to J″ = 16 ← 15 transitions were observed. The vanishing of the Ka = 1, 3, … transitions demonstrates a C2v symmetry complex with a T-shaped alignment of the subunits. The spectroscopic constants were fit using Pickett's SPFIT/SPCAT suite of programs obtaining: 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 = 0.0613(21) kHz, 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, ϕJ = 0.0398(42) Hz, ϕJK = 6.9(9) Hz, and ϕK = −3.592(13) kHz. The 14N nuclear quadrupole coupling constants were fit to χaa = −4.12753(38) MHz and χbb − χcc = 0.103(15) MHz. The small negative inertial defect, Δ0 = −0.66(12) u Å2, indicates a vibrationally averaged planar complex with non-negligible low frequency out-of-plane vibrations. While maintaining near-planar orientation, both binding partners exhibit large-amplitude bending vibrations within the plane. To deal with the intermolecular dynamics, a torsional oscillation model was developed in this work for the structural analysis. According to this model, the vibrational bending amplitude for HCCCN torsional angle is 10.(1)°, with the a-axis of complex; CO2 subtending a 5.4(5)° torsional oscillation angle with the b molecular axis. The 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. High-level MP2 and DFT calculations of structural parameters, rotational constants, and 14N quadrupole coupling strengths were made and the results compared with experimental results.

Original languageEnglish (US)
Pages (from-to)62-72
Number of pages11
JournalJournal of Molecular Spectroscopy
StatePublished - Dec 2017

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Spectroscopy
  • Physical and Theoretical Chemistry


Dive into the research topics of 'Rotational spectrum and structure of the T-shaped cyanoacetylene carbon dioxide complex, HCCCN⋯CO2'. Together they form a unique fingerprint.

Cite this