Molecular recognition of 4′-Nitrobenzo-15-crown-5 by bis(benzimidazolium)propane borontetrafluoride in acetonitrile

ICT based ratiometric sensing due to H-bonding interaction among three different crown ethers (C): Dibenzo-24-crown-8 (DB24C8 or C1), Benzo-15-crown-5 (B15C5 or C2) and 4′-Nitrobenzo-15-crown-5 (4′-NB15C5 or C3) along with the axle bis(benzimidazolium)propane borontetrafluoride (BBIM-propane) (3a-3d) have been studied. The association were initially ascertained from isosbestic formation and later corroborated by iso-emissive formation where C3 fails to establish iso-emissive. Stoichiometry of adducts were 1:1 both in the ground as well as in excited state. The threading or external association was finally distinguished by Monte Carlo simulation and frontier molecular orbital interaction.