Marcin Gronowski

This theoretical study is focused on predicting structures, energetics, and selected spectroscopic constants for a range of 5-atomic chemical species sharing the [C, C, H, N, S] stoichiometry, including thioformyl cyanide and iminoethenethione. An in-depth study carried out on the four most stable isomers have yielded (i) structures and energy for the lowest singlet and triplet excited electronic states; (ii) anharmonic vibrational frequencies and IR absorption intensities for the fundamental, overtone and combination modes; (iii) molecular parameters of interest to microwave spectroscopy: rotational constants, electric dipole moments, and quadrupole coupling constants.

Full text: Journal of Molecular Structure, Volume 1090, 15 June 2015, Pages 76–85

The recent identification of HRgC5N (Rg = Kr, Xe) in a cryogenic matrix calls for an in-depth theoretical study on these compounds. Here we present the results of CCSD(T), MP2, and DFT calculations concerning the molecular structure, stability, and vibrational spectroscopy. The procedure combining CCSD(T) calculations for variable H–Rg distances with the anharmonic description of the corresponding stretching vibration, based on a Morse-type potential energy function, was proposed and has led to good agreement between computational and experimental values for H–Rg stretching frequencies, at relatively low computational costs. High Raman scattering activity of HRgC5N and of its isomers, predicted at the DFT level, gives some prospects for the detection of these molecules with a method alternative to the IR absorption spectroscopy.

Full Text: J. Phys. Chem. A, 2015, 119, pp 2672–2682

A high-level ab initio study was conducted over the range of tetraatomic molecules containing H, C, N, and Mg. Potential energy surfaces were analyzed, leading, for selected molecules, to the optimization of their geometry in the lowest singlet and triplet excited states. Reliable ground state rotational constants are given for the most stable species, namely, HMgNC and HMgCN, together with respective anharmonic vibrational frequencies of fundamental, overtone, and combination bands. In addition, potential energy surfaces describing the interaction of HCN or HNC with a single magnesium atom have been investigated.

Full text: J. Phys. Chem. A, 2013, 117 (21), pp 4455–4461

Products of the vacuum-UV photolysis of cyanodiacetylene HC₅N in solid argon —the anion C₅N−, imine HNC₅, and the branched carbene C₄(H)CN —have been identified by IR absorption spectroscopy, in addition to the already discovered isonitrile HC4NC. Spectral assignments were assisted by deuterium substitution experiments, by BD(T) calculations, and by the results of a recent density functional theory study.
Full text: J. Chem. Phys. 128 (2008) 154303

Coupled cluster calculations were carried out for C₃N−, CCNC−, C₃N, CCNC, C₃N+, and C₃O. They support the experimental identification of the C₃N− ion by means of matrix isolation infrared IR spectroscopy. The anion was generated in electric discharges through the cyanoacetylene isotopomers HC₃¹⁴N, HC₃¹⁵N, and ²HC₃N, trapped in cryogenic rare gas matrices Ne, Ar, Kr, anddetected via its two most intense IR absorption bands, assigned to the 1 and 2 stretching vibrations. C₃N− appears to be quite a stable anion, with a vertical detachment energy predicted to be as high as 4.42 eV. A large equilibrium electric dipole moment of 3.10 D facilitates the investigation of C₃N− by microwave spectroscopy and radio astronomy. Various structural parameters and spectroscopic properties have been calculated for all tetra-atomic species considered.
Full text: J. Chem. Phys 128 (2008) 154305

Following the measurements of UV and mid-IR spectra of cyanodiacetylene, H-CC₂-CN, isolated in low temperature Ar matrices, the first photochemical study on this compound and on its ²H isotopomer was carried out with the laser light tuned to 267 nm and with far-UV discharge lamps. Evidence for the formation of isocyanodiacetylene, H-CC₂-CN, was found in infrared absorption spectra interpreted with the aid of available theoretical predictions.
Full text: J. Chem. Phys. 126 (2007) 164301

Recent ab initio (coupled-clusters) and density functional theory studies on cyanodiacetylene isomers are extended here to yield the quantities of direct interest to future spectroscopic investigations. A bond lengths scaling procedure was developed to obtain the corrected molecular geometries. These, together with calculated vibration–rotation coupling constants, yielded the ground-level rotational constants for seven most stable isomeric species of the HC5N stoichiometry. Former calculations regarding the vibrational transitions of these molecules are complemented here with predictions on Raman scattering activities, and on isotopic (2H, 15N) effects in IR absorption and Raman spectra.
Full text: J. Mol. Struct. 834-836 (2007) 102

Coupled-clusters CCSD(T)/cc-pVTZ calculations have been carried out on several lowest energy isomers of cyanodiacetylene H–CC–CC–CN, previously selected in an extensive DFT study. Apart from the izonitrile H–CC–CC–NC, branched species CC(H)CCCN and CCCC(H)CN are found to be of particular importance, less stable than cyanodiacetylene by 48.5 and 51.0 kcal/mol, respectively. Harmonic frequencies and IR absorption intensities of vibrational fundamentals were predicted at the B3LYP/aug-cc-pVTZ level.
Full text: Chem. Phys. Lett. 428 (2006) 245