Electro-optical, electronic and conformational transitions of interstellar alkyl molecules at different temperatures: An ab-initio study

In this paper, electronic structures of iso-propyl cyanide (i-C3H7CN), gauche-normal-propyl cyanide (g-n-C3H7CN) and anti-normal-propyl cyanide (a-n-C3H7CN) have been optimized using DFT/B3LYP/aug-cc-pVDZ and DFT/CAM-B3LYP/aug-cc-pVDZ methods in neutral and anionic states. Electro-optical properties, HOMO, LUMO and MEP surfaces have been computed in order to check the optical behaviour and chemical reactivity of these interstellar molecules. The a-n-C3H7CN molecule exhibits better electro-optical behaviour than g-n-C3H7CN and iso-C3H7CN molecules. Global reactivity descriptors, adiabatic and vertical electron affinities of these straight and branched alkyl molecules have been investigated. These molecules have negative electron affinities, which means that they emit energy in anionic form. The distribution of chemical bonding and electron lone pairs inside molecules has been discussed using ELF map. Infrared and absorption spectra of these interstellar molecules have been studied in the light of experimental data. Further, formations of g-n-C3H7CN from i-C3H7CN, a-n-C3H7CN from i-C3H7CN and a-n-C3H7CN from g-n-C3H7CN have been examined using transition state at 10 ​K, 298.15 ​K and 500 ​K temperatures. Mechanism of formation of g-n-C3H7CN and a-n-C3H7CN from i-C3H7CN at 10 ​K, 298.15 ​K and 500 ​K temperatures along with their physico-chemical properties have been elucidated.