1-Oxo-1H-phenalene-2,3-dicarbonitrile Based Sensor for Selective Detection of Cyanide ions in Industrial Waste

Abstract

A phenalenedicarbonitrile (1-oxo-1H-phenalene-2,3-dicarbonitrile) based probe 3 has been synthesized by following oxidative nucleophilic substitution of aromatic hydrogen reaction (SNArH) also called green reaction. Probe 3 is found to be selective towards detection of cyanide (CN−) ions even in the presence of other anions. It originally gives pink color in H2O-CH3CN (1:9, v/v) and is found to be non-emissive when observed under Ultraviolet (UV) lamp. Upon adding of CN− ions to solution of probe 3 (20 µM, H2O-CH3CN (1:9, v/v)) the pink color of probe 3 is bleached out and bright yellow emission is attained when observed under UV-lamp. The colorimetric changes are also accompanied by spectral changes. The absorption and low-intensity emission maximum of probe 3 have been observed at 527 nm and 567 nm, respectively but upon adding CN−, the absorption at 527 nm is quenched with formation of new band at 454 nm whereas enhancement in emission band at 567 nm is observed. Probe 3 shows strong binding for CN− ions and binding constant is calculated to be 1.1 × 104 M−1 through fluorescence titration profile and can detect CN− as low as 5.5 × 10−8 M. Binding mechanism of CN− with probe 3 is analyzed through infra-red spectroscopy and proton NMR titration, which reveals that CN− ions attack chemodosimetrically on -C=O of probe 3 to form cyanohydrin. Probe 3 is also used for detection of CN− in industrial waste water. The spectral changes of probe 3 in presence of a specific ion have been used to design a 1-to-2 decoder.