Highly selective colorimetric detection of cyanide anions in aqueous media by triphenylamine and phenanthro(9,10-d) imidazole based probes

Two novel fluorescent probes based on triphenylamine (TPC) and phenanthro(9,10-d-imidazole) (PITP) have been synthesized and studied as cyanide selective indicators in aqueous media. Complete colour bleaching was observed due to the nucleophilic addition of cyanide to the 2-vinylmalononitrile of TPC, which results in the disruption of the extended conjugation and turns off the intramolecular charge transfer (ICT) process. Furthermore, a visible color change was observed with a large Stokes shift (108 nm) upon the addition of cyanide anions to PITP, due to the formation of hydrogen bonding between the CN- anion and -NH of PITP, which increased the electron density on the donor moiety and induced strong ICT.