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 (KQO-CN-CN−=39,317M−1) and detection of limit (DOL=1.2μM) for CN− than that of QO-Cl, (KQO-Cl-CN−=1950M−1; DOL=69μM). This can be attributed to the higher electron withdrawing nature of CN than the moderately electron-withdrawing substituent Cl.