A structurally characterized new oxo-chromene functionalized rhodamine derivative L1 exhibits high selectivity toward Sn(4+) by forming a 1:1 complex, among other biologically important metal ions, as studied by fluorescence, absorption, and HRMS spectroscopy. Complexing with Sn(4+) triggers the formation of a highly fluorescent ring-open form which is pink in color. The sensor shows extremely high fluorescence enhancement upon complexation with Sn(4+), and it can be used as a "naked-eye" sensor. DFT computational studies carried out in mimicking the formation of a 1:1 complex between L1 and Sn(4+) resulted in a nearly planar pentacoordinate Sn(IV) complex. Studies reveal that the in situ prepared L1-Sn complex is selectively and fully reversible in presence of sulfide anions. Further, confocal microscopic studies confirmed that the receptor shows in vitro detection of Sn(4+) ions in RAW cells.

Recently, the design, synthesis and development of chemodosimeters for hydrazine with high selectivity and sensitivity has attracted tremendous attention due to its major contributions to human health and disease including applications in various platforms. In this review, we recapitulate different strategies for the design of reaction‐based colorimetric and fluorometric probes for the detection of hydrazine and their applications in hydrazine sensing in living systems. The sensing strategies for hydrazine have been divided into six categories: (a) cleavage of the acetoxy group; (b) the nucleophilic addition‐elimination on keto ester; (c) the nucleophilic substitution‐elimination to tandem cyclization on halo‐ester; (d) the nucleophilic addition reaction to phthalimide derivative to phthalhydrazide; (e) the chemical displacement of active methylene compound to hydrazone derivative and (f) Other different approaches. Additionally, a variety of techniques have been devised here for the detection of hydrazine over other comparable ions and neutral amines.

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A BODIPY-based pyrenebutyrate-linked (BPB) chromogenic and fluorogenic probe was synthesized and characterized for the specific detection of hydrazine.

Designing a fluorogenic probe for the determination of Pd2+ is a challenging analytical task. Pd2+ is a potentially toxic and harmful substance even at a very low level of contamination in the end product. Herein, a promising spirolactam-functionalized chemosensor, rhodamine-appended benzophenone (HBR), is designed and characterized by spectroscopic (1H NMR, 13C NMR, ESI-MS, and FT-IR) data along with the single-crystal X-ray diffraction technique. It acts as a highly sensitive and selective fluorogenic chemosensor for Pd2+ ions over other environmentally relevant cations in aqueous ethanol (1:1, v/v) at pH 7.4. The limit of detection (LOD) is 34 nM that is far below the WHO recommended Pd uptake (47 μM). The plausible mechanism involves the specific binding of HBR with Pd2+ and the formation of 1:1 stoichiometry of the complex, which has been supported by ESI-MS, FT-IR data, Job plot, and association constant data (Benesi–Hildebrand plot). The computation study has been attempted to explain the ring cleavage fluorescence enhancement scheme of HBR upon binding with Pd2+. Furthermore, this “turn-on” probe has successfully applied to image the Pd2+ ion in cultured MDA-MB-231 cells.