Formation of complex organics by covalent and non-covalent interactions of the sequential reactions of 1–4 acrylonitrile molecules with the benzonitrile radical cation

Abstract

Benzonitrile molecules are present in ionizing environments including interstellar clouds and solar nebulae, where their ions can form adducts with neutral molecules such as acrylonitrile leading to the formation of a variety of nitrogen-containing complex organics. Herein, we report on the formation of complex organics by the sequential reactions of 1–4 acrylonitrile (C₃NH₃) molecules with the benzonitrile radical cation (C₇NH₅⁺˙). The results reveal the formation of the covalently bonded N-acrylonitrile-benzonitrile radical cation (C₁₀N₂H₈⁺˙) with a rate coefficient of 2.2 (±0.4) × 10⁻¹¹ cm³ s⁻¹ at 423 K and a calculated collision cross-section of 73.8 Ų in good agreement with the measured cross-section of 70.7 Ų of the C₁₀N₂H₈⁺˙ adduct. Subsequent reversible association of 1–3 acrylonitrile molecules with the N-acrylonitrile-benzonitrile radical cation (C₁₀N₂H₈⁺˙) at lower temperatures (250–200 K) results in the formation of the N-rich clusters (C₁₀N₂H₈⁺˙)(C₃NH₃)_1–3 which can be enhanced in the very cold cores of the interstellar medium (ISM) and could offer unique potential candidates for the substantial amount of nitrogen carriers detected in the emission spectra of the ISM. The observed N-acrylonitrile-benzonitrile covalent adduct and its associated acrylonitrile clusters could have significant implications in the formation of different types of complex organics in different regions of outer space. It is anticipated that the current results would have direct implications in the search for nitrogen-containing complex organics in space.