Dicyano-benzimidazole molecules as ratiometric and colorimetric sensors for anions

Abstract

Excited State Intramolecular Proton Transfer based benzimidazole derivative having push-pull effect has been synthesized and investigated their photophysical behavior towards various anions. The probe 2 has been used for selective estimation of F- and CN- anions and signaled the binding event through formation of new absorption band at 465 nm. The probe 2 opens different emission channels at 425 nm in the presence of CN- ions and two new emission bands at 435 nm and 365 nm in case of F- ions. The probe 2 behaved as chemodosimeter for CN-ions which have been proved by 1H NMR and whereas fluoride caused hydrogen bonding interactions with probe 2 and restricted the ESIPT emission at 505 nm from OH to nitrogen of benzimidazole moiety to release its enol emission. The differential behavior of F- ions and CN- have been confirmed through DFT calculations.