Supplementary material from "Benzimidazolium quaternary ammonium salts: synthesis, single crystal and Hirshfeld surface exploration supported by theoretical analysis"

Owing to the broad applications of quaternary ammonium salts (QAS), we present the synthesis of benzimidazolium-based analogs with variation in the alkyl and alkoxy group at N-1 and N-3 positions. All the compounds were characterized by spectroscopic techniques and found stable to air and moisture both in the solid and solution state. Moreover, molecular structures were established through single-crystal X-ray diffraction studies. The crystal packing of the compounds was stabilized by numerous intermolecular interactions explored by Hirshfeld surface analysis. The enrichment ratio was calculated for the pairs of chemical species to acquire the highest propensity to form contacts. Void analysis was carried out to check the mechanical response of the compounds. Furthermore, theoretical investigations were also performed to explore the optoelectronic properties of compounds. NPA analysis has been conducted to evaluate the distribution of charges on the synthesized compounds, whereas high band gaps of the synthesized compounds by FMO analysis indicated their stability. NLO analysis revealed that the synthesized QAS demonstrates significantly improved NLO behaviour than the standard Urea.