Quinone based oligomeric sensors as colorimetric probes for cyanide anion: Effects of solvent medium and substituent on sensing

Abstract The main objective of the present study is to understand the structure-property relationships of sensor capable of colorimetric response, upon the addition of particular anions, due to hydrogen-bonding association between sensor and anion. Further, hydrogen-bonding association between sensor and anion, and thereby colorimetric response of the receptor in various solvent media was also targeted. For this, we have synthesized chloro-substituted quinone based oligomer sensor (QO-Cl) and cyano-substituted quinone based oligomer sensor (QO-CN), which contain the thiourea as a binding site. These oligomeric sensors were exploited as colorimetric sensors for cyanide anion [CN − ]. Further, the sensing abilities of these sensors for CN − recognition in various solvents were monitored to investigate the influence of solvent on the hydrogen bonding association between sensor and anion. Our colorimetric and spectrometric results unveiled that the QO-CN sensor has shown the better binding constant (K QO-CN - CN  − = 39,317 M − 1 ) and detection of limit (DOL = 1.2 μM) for CN − than that of QO-Cl, (K QO-Cl - CN  − = 1950 M − 1 ; DOL = 69 μM). This can be attributed to the higher electron withdrawing nature of C N than the moderately electron-withdrawing substituent Cl.