Perylene diimide–based near-IR ratiometric sensor for detection of Cu2+ ions: Ensemble for discrimination of CN- and S2- ions
In this study, we have designed and synthesized perylene diimide-based novel chromo-fluorescent chemosensor (TBP-PDI), which shows selective ratiometric fluorescent ‘turn-on’ (F482/F680 nm) and colorimetric (A476/A630) response on addition of Cu2+ ions in HEPES buffered: CH3CN (4:6, v/v, pH 7.2) media and CH3CN. The detection limits of TBP-PDI for Cu2+ were found to be 4.8 µM / 2.5 nM using fluorescence mode and 5.35 µM/ 0.71 nM using absornace mode in these solvents, respectively. The complexation of TBP-PDI with Cu2+ was further supported by NMR, dynamic light scattering (DLS), cyclic voltammetric (CV) and differential pulse voltametric (DPV) studies. The limit of detection for Cu2+ using DPV is 0.46 µM. This perylene diimide–Cu2+ based ensemble (TBP-PDI–Cu2+) was further used as ‘turn-on’ type chemosensor for CN- ions with detection limit of 7.38 nM /3.98 µM and as ‘turn-off’ type chemosensor for S2-with detection limit of 35 µM. These changes can be explained by the fact that CN- interacts with TBP-PDI–Cu2+ ensemble through coordination with Cu2+ via displacement of solvent molecule whereas S2- interacts with TBP-PDI–Cu2+ ensemble via sequestration of Cu2+ from binding pocket of ensemble.