Synthesis, Photophysical Properties, and Biological Importance of Pyrimidinium Ionic Liquids

Abstract

AbstractThe synthesis of a family of organic salts and ionic liquids using pyrimidine as a heterocyclic core, an essential structural subunit of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) has been achieved. The pyrimidine‐containing ionic liquids coupled with tetrafluoroborate and bis(trifluoromethane)sulfonamide ( and ) as counter anions were synthesised via the nucleophilic addition of one of the N‐atoms of a pyrimidine to the arylalkyl and aryloxy alkyl halides followed by anion metathesis using highly stable and non‐hygroscopic sodium tetrafluoroborate (NaBF4) and bis(trifluoromethane)sulfonimide lithium salt (LiN(SO2CF3)2) in good to excellent yield. Further, the synthesised ionic liquids were utilised to explore their in vitro antibacterial activities along with evaluation of their photophysical, physical and thermal properties. The assessment of in vitro minimum inhibitory concentration (MIC) study against several pathogenic bacteria revealed that the 1‐(3‐phenylpropyl)pyrimidin‐1‐ium tetrafluoroborate (4 c: [(PhC3)Pym]BF4) is moderately active against Gram‐negative P. aruginosa bacteria (MIC=16 μg/mL) while 1‐phenethylpyrimidin‐1‐ium tetrafluoroborate (4b: [(PhC2)Pym]BF4), 1‐(3‐phenylpropyl)pyrimidin‐1‐ium tetrafluoroborate (4 c: [(PhC3)Pym]BF4), 1‐(phenoxypropyl)pyrimidin‐1‐ium tetrafluoroborate (4 d: [(PhOC3)Pym]BF4) and 1‐(phenoxybutyl)pyrimidin‐1‐ium tetrafluoroborate (4 e: [(PhOC4)Pym]BF4) exhibit moderate to good bioactivities against Gram‐positive S. aureus, and B. pumilis, respectively.