A ferrocene-based chemo-dosimeter for colorimetric and electrochemical detection of cyanide and its estimation in cassava flour†

Abstract

A simple chemo-dosimeter VDP2 bearing a ferrocene moiety was designed, synthesized, and characterized, and exhibited both chromogenic and electrochemical responses selectively for CN⁻ in H₂O–DMSO (9 : 1, v/v) medium. The probe VDP2 showed an instantaneous color change from colorless to yellow with CN⁻ that can readily be observed visually. The deprotonation of the benzimidazole –NH, followed by nucleophilic addition of CN⁻ to the olefinic C-atom, as evidenced by ¹H and ¹³C NMR titration experiments, caused the colorimetric and electrochemical responses. The mass spectral study, CV, FTIR and Mulliken charges computed well supported the proposed mechanism. The electrochemical limit of detection was calculated to be 72 nM. The results of DFT and TD-DFT calculations suggested that the colorless nature of the probe VDP2 is due to weak intramolecular charge transfer (ICT) transition and the yellow color of the VDP2+CN adduct is due to through-space ICT transition. Above all, the probe could be an ideal candidate for monitoring cyanide in water samples and cassava flour with practical significance. A simple and convenient colorimetric method was developed to determine cyanide content in cassava flour.