Microstructural (self-assembly) and optical based discrimination of Hg2+, CN- and Hg(CN)2 ion-pair; Hg2+ promoted-ESIPT assisted guanylation of thiourea

A multifunctional self-assembled dual-chemosensor DTS was synthesized and used for optical and microstructural based discrimination of Hg2+, CN- ions and Hg(CN)(2) ion-pair. The addition of Hg2+ ions to the CH3CN solution of DTS promotes the ESIPT phenomena (emission peak at 458 nm red shifted to 510 nm; increase in absorption between 400 and 480 nm), followed by cyclization (guanylation) reaction with concomitant desulfurization (decrease of emission intensity at 510 nm and minor increase at 410 nm; increase and decrease in absorbance intensity at 270 and 325 nm, respectively). In contrast, CN-induced deprotonation in DTS results in simultaneous decrease in absorbance at 310 nm and increase in absorbance at 385 nm and 425-475 nm and fluorescence enhancement at lambda(em) 452 nm. On the addition of Hg(CN)(2) ion pair, DTS shows apparent effect of both Hg2+ and CN- ions. The mechanism of interaction of DTS with Hg2+, CN- and Hg(CN)(2) has been established by detailed H-1 NMR and ESI-MS studies. DTS in CH3CN shows flake like morphology which undergoes analyte induced self-assembly to form a bunch of nanorods with Hg2+; segregated nanorods with curvy ends with CN- and spherical structures with Hg(CN)(2) ion pair.