Crystallographic evidence for resonance assisted H-Bonding effect in selective colorimetric detection of cyanide by arylamino-naphthoquinones

Abstract

Five new chemo-receptors, based on arylamino-naphthoquinone, possessing electron donating and electron withdrawing substituents have been prepared by single step green method. These receptors are found to be highly selective and sensitive towards cyanide ions in aqueous HEPES buffer solution (pH 7.2). The mechanism, as evidenced by 1H NMR, electrochemical and theoretical studies, is based on instantaneous deprotonation of –NH moiety by cyanide, which is enabled by substituent dependent resonance effect of the phenyl ring. This is confirmed by single crystal XRD data. The detection limit is calculated to be in the order of 10−8 M, which is much lower than the permissible limit of cyanide in drinking water set by WHO (1.9 × 10−6 M).