The eight lowest-energy vibrational states of benzonitrile: analysis of Coriolis and Darling-Dennison couplings by millimeter-wave and far-infrared spectroscopy

Zdanovskaia, Maria A.; Martin-Drumel, Marie-Aline; Kisiel, Zbigniew; Pirali, Olivier; Esselman, Brian J.; Woods, R. Claude; McMahon, Robert J.

doi:10.1016/j.jms.2021.111568

Cited by 13 publications

(22 citation statements)

References 68 publications

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“…These two low-frequency vibrational modes involve the bending of the cyano-functional group as a rigid entity. Similar low-frequency vibrational progressions have previously been experimentally and theoretically observed in benzonitrile by several workers. − …”

Section: Resultssupporting

confidence: 88%

Negative Ion Photoelectron Spectra of Deprotonated Benzonitrile Isomers via Computation of Franck–Condon Factors

2022

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Negative ion photoelectron spectra of ortho (o-), meta (m-), and para (p-) deprotonated benzonitrile (o-, m-, p-C 6 H 4 (CN) − ) isomers as well as the associated thermochemical values corresponding to deprotonation at o-, m-, and p-positions in C 6 H 5 (CN) are presented. Quantum mechanical results based on the density functional theory (DFT) utilizing the aug-cc-pVQZ basis set indicate that the o-, m-, p-C 6 H 4 (CN) • radicals have electron affinity values (EAs) of 1.901, 1.778, and 1.789 eV, respectively. The computed Franck−Condon (FC) factors give rise to o-, m-, and p-C 6 H 4 (CN) − negative ion spectra with FC active ring distortion vibrational modes with harmonic vibrational frequencies of ∼450, 760, and 1000 cm −1 as the dominant vibrational progressions. Deprotonation at the o-, m-, and ppositions in C 6 H 5 (CN) results in calculated gas-phase acidity values (Δ acid H 298K o ) of 383.9, 385.7, and 385.3 kcal mol −1 , respectively. The calculated Δ acid H 298K o is in close agreement with the previously reported high-pressure mass spectrometry experimental value of 383.4.0 ± 4.4 kcal mol −1 . The computed Δ acid H 298K o and EAs are utilized to estimate the bond dissociation energy (DH 298 (H-C 6 H 4 CN)) associated with the formation o-, m-, and p-C 6 H 4 (CN) • using the negative ion thermochemical cycle: DH 298 (C 6 H 5 CN) = Δ acid H 298K o (H-C 6 H 4 (CN) + EA (C 6 H 5 CN) • − IP(H). The respective values of DH 298 (H-C 6 H 4 CN) corresponding to the formation of ortho, meta, and para C 6 H 4 (CN) radicals are 114.15, 113.11, and 113.51 kcal mol −1 .

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Section: Resultssupporting

confidence: 88%

Negative Ion Photoelectron Spectra of Deprotonated Benzonitrile Isomers via Computation of Franck–Condon Factors

2022

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“…Despite the complicating interaction with ν 26 (A″), this tetrad can be addressed using the same general methodology recently employed with benzonitrile, where the triad consisting of the overtones and simple combination of the two lowest-lying states is analyzed very successfully. 50 In that study, the harmonic and anharmonic vibrational constants for the states involved are well predicted by the xguinea routine of CFOUR, as was the Darling−Dennison coupling term connecting the two overtone states. Furthermore, it has been found that the higher-order Coriolis coupling coefficients, e.g., G a J or F bc , for the triad scale rather closely as a factor of 2 from the corresponding ones of the dyad.…”

Section: ■ Experimental and Theoretical Methodsmentioning

confidence: 74%

“…This tetrad is expected to be well-isolated from other vibrationally excited states and of sufficient intensity that the rotational spectra of all four states can be measured, assigned, and least-squares fit, using the spectral data we have already acquired. Despite the complicating interaction with ν 26 (A″), this tetrad can be addressed using the same general methodology recently employed with benzonitrile, where the triad consisting of the overtones and simple combination of the two lowest-lying states is analyzed very successfully . In that study, the harmonic and anharmonic vibrational constants for the states involved are well predicted by the xguinea routine of CFOUR, as was the Darling–Dennison coupling term connecting the two overtone states.…”

Section: Resultsmentioning

confidence: 99%

Synthesis, Purification, and Rotational Spectroscopy of 1-Cyanocyclobutene (C₅H₅N)

et al. 2022

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The rotational spectrum of 1-cyanocyclobutene from 130 to 360 GHz has been observed, assigned, and least-squares fit for the ground state and the two lowest-energy vibrationally excited states. Synthesis by UV photochemical dimerization of acrylonitrile and subsequent base-catalyzed dehydrocyanation affords a highly pure sample, yielding several thousand observable rotational transitions for this small organic nitrile. Over 2500 a-type, R-branch transitions of the ground state have been least-squares fit to low error with partial-octic A- and S-reduced Hamiltonians, providing precise determinations of the corresponding spectroscopic constants. In both reductions, computed spectroscopic constants are in close agreement with their experimentally determined counterparts. Two vibrationally excited states (ν27 and ν17) form a Coriolis-coupled dyad, displaying many a-type and b-type local resonances and related nominal interstate transitions. Somewhat unexpectedly, despite the very small permanent b-axis dipole moment, a number of b-type transitions could be observed for the ν17 state; this is explained in terms of state mixing by the Coriolis perturbations. Over 2200 transitions for each of these states have been least-squares fit to a low-error, two-state, partial-octic, A-reduced Hamiltonian with nine Coriolis-coupling terms (G a , Ga J , G a K , G a JJ , F bc , F bc K , G b , G b J , and F ac ). The availability of so many observed rotational transitions, including resonant transitions and nominal interstate transitions, enables a very accurate and precise determination of the energy difference (ΔE 27,17 = 14.0588093 (43) cm–1) between ν27 and ν17. The spectroscopic constants presented herein provide a starting point for future astronomical searches for 1-cyanocyclobutene.

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“…A partial octic, Corioliscoupled dyad Hamiltonian was employed, similar to our previous works involving analogous nitrile vibrational modes. [24][25][26][27]30,45,46 From this initial prediction and subsequent measurement, assignment, and least-squares fitting of the millimeter-wave data, spectroscopic constants were obtained, including an accurate and precise energy separation between ν 24 and ν 17 . This preliminary least-squares fit provided the foundation for the subsequent analysis of the high-resolution infrared spectrum obtained from CLS.…”

Section: ■ Experimental Methodsmentioning

confidence: 99%

Millimeter-Wave and High-Resolution Infrared Spectroscopy of 2-Furonitrile─A Highly Polar Substituted Furan

et al. 2023

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The rotational spectrum of 2-furonitrile (2-cyanofuran) has been obtained from 140 to 750 GHz, capturing its most intense rotational transitions at ambient temperature. 2-Furonitrile is one of two isomeric cyano-substituted furan derivatives, both of which possess a substantial dipole moment due to the cyano group. The large dipole of 2-furonitrile allowed over 10 000 rotational transitions of its ground vibrational state to be observed and least-squares fit to partial octic, A-and S-reduced Hamiltonians with low statistical uncertainty (σ fit = 40 kHz). The high-resolution infrared spectrum, obtained at the Canadian Light Source, allowed for accurate and precise determination of the band origins of its three lowest-energy fundamental modes (ν 24 , ν 17 , and ν 23 ). Similar to other cyanoarenes, the first two fundamental modes (ν 24, A″, and ν 17 , A′, for 2-furonitrile) form an a-and b-axis Coriolis-coupled dyad. More than 7000 transitions from each of these fundamental states were fit to an octic A-reduced Hamiltonian (σ fit = 48 kHz), and the combined spectroscopic analysis determines fundamental energies of 160.1645522 (26) cm −1 and 171.9436561 (25) cm −1 for ν 24 and ν 17 , respectively. The least-squares fitting of this Coriolis-coupled dyad required 11 coupling terms,J , and F ac K . Using both the rotational and high-resolution infrared spectra, a preliminary least-squares fit was obtained for ν 23 , providing its band origin of 456.7912716 (57) cm −1 . The transition frequencies and spectroscopic constants provided in this work, when combined with theoretical or experimental nuclear quadrupole coupling constants, will provide the foundation for future radioastronomical searches for 2-furonitrile across the frequency range of currently available radiotelescopes.

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The eight lowest-energy vibrational states of benzonitrile: analysis of Coriolis and Darling-Dennison couplings by millimeter-wave and far-infrared spectroscopy

Cited by 13 publications

References 68 publications

Negative Ion Photoelectron Spectra of Deprotonated Benzonitrile Isomers via Computation of Franck–Condon Factors

Negative Ion Photoelectron Spectra of Deprotonated Benzonitrile Isomers via Computation of Franck–Condon Factors

Synthesis, Purification, and Rotational Spectroscopy of 1-Cyanocyclobutene (C₅H₅N)

Millimeter-Wave and High-Resolution Infrared Spectroscopy of 2-Furonitrile─A Highly Polar Substituted Furan

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The eight lowest-energy vibrational states of benzonitrile: analysis of Coriolis and Darling-Dennison couplings by millimeter-wave and far-infrared spectroscopy

Cited by 13 publications

References 68 publications

Negative Ion Photoelectron Spectra of Deprotonated Benzonitrile Isomers via Computation of Franck–Condon Factors

Negative Ion Photoelectron Spectra of Deprotonated Benzonitrile Isomers via Computation of Franck–Condon Factors

Synthesis, Purification, and Rotational Spectroscopy of 1-Cyanocyclobutene (C5H5N)

Millimeter-Wave and High-Resolution Infrared Spectroscopy of 2-Furonitrile─A Highly Polar Substituted Furan

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Synthesis, Purification, and Rotational Spectroscopy of 1-Cyanocyclobutene (C₅H₅N)