Quantum chemical studies on the simultaneous interaction of thiophene and pyridine with ionic liquid



The simultaneous interaction of thiophene and pyridine with different ionic liquids:1-butyl-1-methylpyrrolidinium tetrafluoroborate([BPYRO][BF4]),1-butyl-1-methylpyrrolidinium hexafluoro-phosphate ([BPYRO][PF6]), 1-butyl-4-methylpyridinium tetrafluoroborate ([BPY][BF4]), 1-butyl-4-methylpyridinium hexafluorophosphate ([BPY][PF6]) and 1-benzyl-3-methylimidazolium tetrafluoroborate ([BeMIM][BF4]) were investigated using quantum chemical calculations. A three-tier approach comprising of partial charges, interaction energies and sigma profile generation using conductor-like screening model for real solvents (COSMO-RS) was chosen to study the systems. A quantitative attempt based on the CH-π interaction in ionic liquid; thiophene–pyridine complexes gave the interaction energies of ILs in the order: [BPY][BF4] > [BPYRO][PF6] > [BeMIM][BF4] > [BPY][PF6] > [BPYRO][BF4]. An inverse relation was observed between the activity coefficient at infinite dilution predicted via COSMO-RS–based model and interaction energies. The dominance of CH-π interaction was evident from the sigma profiles of ionic liquid together with thiophene and pyridine. © 2010 American Institute of Chemical Engineers AIChE J, 2011