Gas‐Phase Infrared Spectra of Three Compounds of Astrochemical Interest: Vinyl, Allenyl, and Propargyl Isocyanides

Abstract

Isocyanides, isomers of the cyanides detected in the interstellar medium, are also possible components of this medium. The infrared spectra (5000-500 cm(-1) ) of gaseous vinyl isocyanide, allenyl isocyanide, and propargyl isocyanide have been recorded at 0.1 cm(-1) resolution. When prepared on a gram scale to produce a partial pressure of 10 mbar after evaporation in the cell, these three isocyanides, which have previously been reported to be kinetically unstable, do not display any sign of decomposition when recording the spectra. Geometry optimizations and harmonic and anharmonic vibrational frequencies were calculated using the LCCSD(T) method with the cc-pVTZ basis set. Anharmonic frequencies of fundamental, overtone, and combination transitions were calculated using a variational approach implemented in the P Anhar.v2.0 code, to assign the experimental data for each compound. These results improve our knowledge of these under-investigated compounds and pave the way for other physicochemical studies on functionalized isocyanides.

Density Functional Exploration of C4H3N Isomers

“…A similar energy difference was reported at the 3-21G level in the context of calculating the ring strain energy of cyclopropene derivatives . CAM-B3LYP/6-311g­(d,p)-based predictions for the isocyanides 6 and 10 have been reported recently in support of IR measurements and include bond distance and angle information . Ionization energies of these latter species were calculated in support of photoelectron spectroscopy measurements.…”

“…47 CAM-B3LYP/6-311g(d,p)-based predictions for the isocyanides 6 and 10 have been reported recently in support of IR measurements and include bond distance and angle information. 48 Ionization energies of these latter species were calculated 49 in support of photoelectron spectroscopy measurements.…”

Exploring molecular complexity with ALMA (EMoCA): complex isocyanides in Sgr B2(N)

“…Additional data were taken from Bestmann & Dreizler (1982). Vibrational corrections to the partition function were evaluated from Benidar et al (2015).…”

Theoretical Investigation of the Infrared Spectrum of 5‐Bromo‐2,4‐pentadiynenitrile from a CCSD(T)/B3LYP Anharmonic Potential

“…The accuracy of the methods used, has been enhanced by considering the irreducible representations involved, allowing the diagonalization of larger vibrational spaces. Our variational and variational–perturbational approaches, have already allowed the complete assignment of many observed spectra or, better yet, arisen from new experimental studies by revisiting their IR spectra . Our aim is to provide an accurate roadmap of the computed IR spectrum of BrC 5 N that shall guide spectroscopists to identify and highlight low‐intensity bands in regions that have not been completely studied so far for this molecule.…”

“…The accuracy of the methods used, has been enhanced by considering the irreducible representationsi nvolved, allowing the diagonalization of larger vibrational spaces. Our variational andv ariational-perturbational approaches, have already allowed the complete assignment of many observed spectra [6][7][8][9][10][11][12][13] or,b etter yet, arisen from new experimental studies by revisiting their IR spectra. [14][15][16] Our aim is On the grounds of ah ybrid CCSD(T)/B3LYP/aug-cc-pVTZ anharmonic potential and the use of av ariational and variationalperturbational methods, the IR spectrao f5 -bromo-2,4-pentadiynenitrile (BrC 5 N) is revisited in the mid-infrared region up to 4500 cm À1 .Aposition andi ntensity analysis of our theoretical results allow us to assign the fundamental bands together with their combinationsa nd overtones, in the aforementioned range of frequencies.…”