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.

Coumarinyl-rhodamine, HCR, served as an extremely selective sensor for Pd2+ ions in ethanol/H2O (8 : 2, v/v, HEPES buffer, pH 7.2) solution and the limit of detection (LOD) was 18.8 nM (3σ method).

A novel water soluble fluorescent compound methylated polycyclic benzimidazolium ion 4 based on benzimidazolium ion (85 % yield) for the response of Fe3+ has been demonstrated for the first time due to its excellent photophysical properties. The molecule is highly sensitive and selective towards Fe3+. A dramatic fluorescence switch on‐off‐on has been observed during interchange from Fe3+ to EDTAand the detection limit is 15.8 nM (3σ method) for Fe3+ ions. The compound 4 exhibits excellent antimicrobial and anti‐biofilm activities against E.cloacae and S.aureus. Cell imaging and mammalian cell cytotoxicity were also investigated. The synthesized molecule exhibits selective activity toward gram‐positive bacteria than gram‐negative ones among six different bacterial species.

General Remarks1 Characterization data for compounds 3a-3k and 4a-4k 2-8 Characterization data for compounds 5b-5k and 7b-7k 8-14 Copy of 1 H NMR and 13 C 15-26 General Remarks:1 H NMR (200 MHz), 1 H NMR (400 MHz) spectra were recorded on a BRUKER-AC 200MHz.and 400MHz spectrometer. Chemical shifts are reported in ppm from tetramethylsilane with the solvent resonance as the internal standard (deuterochloroform: 7.26 ppm). Data are reported as follows: chemical shifts, multiplicity (s = singlet, d = doublet, t = triplet, m = multiplet, dd = double doublet), coupling constant (Hz). 13 C NMR (50 MHz), 13 C NMR (100MHz) spectra were recorded on a BRUKER-AC 200 MHz and 400MHz Spectrometer with complete proton decoupling. Chemical shifts are reported in ppm from tetramethylsilane with the solvent resonance as the internal standard (deuterochloroform: 77.0 ppm). EIMS (70 ev) spectra were taken using a VG Autospec mass spectrometer. Chromatographic purification was done with either 60-120 or 100-200 mesh silica gel (SRL). For reaction monitoring, precoated silica gel 60 F254 TLC sheets (Merck) were used. Petroleum ether refers to the fraction boiling in the range 60-80 ºC. DMF was dried, distilled and stored over molecular sieves (4 Å). Experimental detailsGeneral procedure for the synthesis of bromoaldehydes (1): 1 A mechanically stirred solution of dimethylformamide(3 mmol) in anhydrous chloroform was cooled in ice bath while phosphorous tribromide (2.7 mmol) was added drop-wise over a period of 15 min. The resulting white suspension was warmed to rt and stirred for additional 20 min. A solution of starting ketomethylene compound (1 mmol) in chloroform was added drop-wise over 10 min. Stirring was continued for 8 h at rt. The reaction mixture was then poured in ice water. Solid sodium bicarbonate was carefully added to neutralize the acids and the mixture was extracted several times with dichloromethane. The organic part was then washed with cold water thoroughly, dried with sodium sulphate and evaporated. Purification of the residue was done by silica gel (60-120 mesh) column chromatography.General procedure for the synthesis ofAromaticbromoaldehydes (2): 2 β-Bromovinyl aldehyde (1 mmol) and DDQ (dichlorodicyano benzoquinone) (6 mmol) were kept in round bottom flask. Then dry benzene (6 mL) was added to the reaction vessel. After that, the total reaction mixture was heated for 16 h then the crude reaction mixture was filtered by dichloromethane (20 mL). The filtrate was dried and the crude product was purified by column chromatography. General procedure for the synthesis of bromoalcohols (3) 1,2Bromoaldehydes1(1 mmol) or aromaticbromoaldehydes2 (1 mmol) and sodiumborohydride (2 equiv.) were kept in two naked flask. Then acetonitrile solvent (5-6 mL) was added and stirred at room temperature for 2-3 h. After completetion of the reaction, the reaction mixture was diluted with water and extracted with ethyl acetate (20 mL × 3) and dried over anhydrous Na 2 SO 4 . The solvent was evaporated and the crude product was puri...