The interaction of explosive and pollutant TNP with the host receptor has been thoroughly explained and characterized by SCXRD and thermodynamic parameters.

Arsenic induced cleavage of the spirolactam ring of a cleft shaped electronically enriched rhodamine based chemoreceptor molecule 3′,6′-bis­(ethylamino)-2-((2-hydroxy-5-methylbenzylidene)­amino)-2′,7′-dimethylspiro­[isoindoline-1,9′-xanthen]-3-one (PBCMERI-23) has been reported in the present work. The developed easy, instant and economic luminescent probe instigate toward unlocking the selectivity for a specific lethal water contaminant such as As­(III) from aqueous media up to a level of 0.164 ppb (beyond the critical limit of the World Health Organization). PBCMERI-23 displays a 2-fold optical response (chromogenic, colorless to reddish pink; fluorogenic, non-blooming fluorescence to yellow emission) via the ring opening phenomenon of the developed chemoreceptor. Owing to the remarkable photophysical and structural properties of the synthesized probe, the recognition event has been turned on in the low energy region. Detailed experimental techniques further supported by theoretical evidence establishes the plausible mechanistic course of the host:guest interaction. The spectrophotometric response of the developed chemoreceptor PBCMERI-23 turns out to be reversible with incremental addition of a stoichiometric amount of I–. The optical recognition phenomenon has been further synchronized and interfaced with molecular logic gate to molecular electronics. To explicate the bioapplicability of PBCMERI-23, varying cell lines, viz., pollen grains of Allamanda puberula (Aapocynaceae), radiator plant (Peperomia pellucida), Poecilia reticulata, Danio rerio, and squamous epithelial cells have been monitored. The probe displays sparkling yellow illumination when the cells were visualized under fluorescence microscope, which confirms its cell permeability and is a biomarker toward intracellular investigation and bio-imaging of As­(III). Furthermore, the chemoreceptor has enormous capability in detecting As­(III) from a series of wastewater specimens with varying pH, which makes the present chemoreceptor PBCMERI-23 unique of its kind.

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A dual-channel chromogenic and fluorogenic fused-aromatic-system-based chemoreceptor (2-(benzo[d]thiazol-2-yl)-1-((pyren-8-yl)methylene)hydrazine) (TyM) was designed for ditopic sensitivity towards heavy and transition metal ions (HTMs), such as Cu, in an aqueous medium and lethal CN in a semi-aqueous medium. The chemoreceptor displayed proclivity towards the targeted analytes with a distinct optical response (yellow to colourless in the case of Cu and yellow to bright red for CN). TyM formed a 2 : 1 adduct with Cu with a detection limit of 40 nM. A 1 : 1 binding stoichiometry was confirmed with the chemoreceptor TyM with CN in sub-nano molar limit of detection. In addition to sophisticated spectroscopic analysis, such as UV-vis, fluorescence, FTIR, H-NMR,C-NMR, ESI-MS, and HRMS, the plausible mechanistic course of sensing was also established from a theoretical perspective. The reversible UV-vis response of the chemoreceptor TyM towards CN and H can mimic different molecular logic functions and therefore can be exploited for designing several complex electronic circuits principally based on Boolean Algebra. In vitro fluorescence imaging in male microspores of seed plants (Bohonia Nigalandra) and Monilia Albicans (diploid fungus) with TyM and Cu confirmed the permeability of the chemoreceptor TyM at the cellular level as well as its ability to investigate transition metals, such as Cu, in biological samples.

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Two chemosensors with varying substitution have been synthesized for selective detection of d10 metal ion analyte Zn2+ and Cd2+ by fluorometric method from aqueous medium at very low limit of detection. Density functional theory (DFT)-based Loewdin spin population analysis reveals that methoxy-substituted chemosensor is much stronger donor than bromo-substituted chemosensor. Eventually, bromo and methoxy substituted chemosensors are moderate and strong donor, respectively, toward selective detection of Cd2+ and Zn2+ by luminescence induced phenomenon (blue for Cd2+ and cyan for Zn2+). The mechanism of sensing could be explained by PET-CHEF-C = N isomerization-ILCT pathway. 1H NMR, ESI-MS and FT-IR has been carried out in order to explore the selective ion sensing mechanism. Intracellular detection of Zn2+ and Cd2+ has been carried out inside androecium (filament and pollens) of Tecoma Stans. Extracellular detection of Zn2+ for yeast cells represents the bio mimetic model experiments toward β-cells exocytosis as a marker of diabetes mellitus. The unprecedented and novel feature of the present biocompatible chemosensor is its application as biosensor to detect in vivo Zn2+ from human urine specimen which could be a next generation diagnostic tool for Pick’s disease.

A urea-functionalized chemoreceptor 1,5-bis(2,4dinitrophenyl)carbonohydrazide (BDC) with versatile applications has been reported in this work. BDC displayed ditopic sensitivity toward toxic industrial pollutants Cu 2+ and CN − from a purely aqueous medium. BDC has been structurally authenticated by ESI-MS, 1 H-NMR, FT-IR, and SCXRD. It can undergo promising "naked eye" detection in the existence of the targeted analytes (pale yellow to dark purple for Cu 2+ and pale yellow to dark brown for CN − ) in the sub-nanomolar detection threshold (Cu 2+ : 46 × 10 −8 M and CN − : 92 × 10 −8 M). The LMCT-ICT and intermolecular H-bonding pathways rationalize the underlying sensing mechanism. A good substantiation of solution-state experimental outcome and theoretical (DFT) evidence further authenticated the recognition pathway. BDC displays reversibility with alternate CN − and Cd 2+ addition up to several cycles that serves to be a reliable system toward mimicking molecular logic gate functions. The cytotoxicity assay of BDC on Bacillus thuringiensis (Bt) exhibit its biocompatibility. Furthermore, BDC can efficiently undergo rapid on-site Cu 2+ and CN − detection in varying real water sources, and interestingly, BDC can recognize the presence of Cu 2+ from biofluids like fetal bovine serum (LOD 13 μM) with a distinct colorimetric response. Moreover, the unprecedented novelty of biocompatible BDC lies in its ability to detect Cu 2+ from a human urine specimen as low as 1.5 μM by concentration-dependent discriminative chromogenic responses. This makes BDC an inimitable exploratory symptomatic tool for Wilson's disease, which to the best of our knowledge to date has been rarely explored in the supramolecular realm. One step ahead, solid-state on-spot chromogenic detection of aqueous Cu 2+ and CN − by the "dip stick" method escalates the practical application of this work.