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• Synthesis of rhodamine based chemosensor extended with Bis-1,2,3-triazole. • Discriminative detection of Fe3+ ions through conversion from non-fluorescent to fluorescent. • pH and reversibility studies were carried out with cysteine. • Bio-imaging studies of chemosensor and its complex with Fe3+ were performed with DL-tumor cell. • Molecular docking was done with Bcl-XL. The discriminatory identification of Fe3+ ions among the series of metal ions in an aqueous medium is a significant importance of chemosensors, a bis-1,2,3-triazole associated with rhodamine (R1) was developed with a perfect hetero-atomic cavity. The chemosensor R1 was synthesized using a simple and well-known click reaction to generate a nitrogen enrich triazoles unit in the R1. Through the naked eyes, Fe3+ ion was detected on the spot at tremendously low concentrations with the alterations of fluorescent from non-fluorescent and colored from colorless R1. After formation of complex R1:Fe3+, it is highly pH sustained range from pH 2.0–10.0 and reversible with cysteine in solution and on a paper strip. The formed complex R1:Fe3+, it exhibits excellent pH stability within the range of pH 2.0–10.0. Moreover, its reversibility can be achieved through interaction with cysteine, both in solution and on a paper strip. R1 was also feasible to detect Fe3+ ions in real water samples. In DL-tumor cells, cytocompatibility was investigated using MTT assay, and found that cell viability was greater than 80 %. The binding interaction of R1 with the crystal structure of the anti-apoptotic protein Bcl-XL (PDB ID: 2YXJ) showed that R1 fits well at the active site of Bcl-XL with binding energy (ΔG) − 10.42 kcal/mol (Ki = 22.97 nM). The result shows that R1 is cytocompatible and may be exploited as a fluorescent probe for selectively detecting Fe3+ in living cells. [ABSTRACT FROM AUTHOR]

A new rhodamine based fluorescent turn on sensor L has been reported as a highly selective and sensitive chemosensor for the Cr 3+ ion in a CH 3 CN-H 2 O solution. In presence of Cr 3+ ion, the strong fluorescence enhancement is attributed due to the interaction of Cr 3+ with L, leading to opening of the spirolactam ring of rhodamine B to the amide form. The Cr 3+ sensing mechanism is also supported by the Job’s plot, ESI-MS, 1 H NMR titration experiments. Importantly, this probe shows high selectivity over other biologically relevant metal ions. Also, anions do not show any effect. In addition, the detection limit is found to be up to 7.5 nM which is acceptable within the EPA (US) limit. The probe is also able to function within a broad biological pH range of 4–8. Furthermore, the probe L shows cellular penetrability for its potential use in confocal cell imaging studies. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new sensor, RT4 detecting Cu2+ and Fe3+ simultaneously with LOD values of 0.24 µM and 0.18 µM respectively. • MS, FTIR, 1H NMR spectra and DFT studies showing the possible binding mechanism of RT4 towards Cu2+ and Fe3+. • Inexpensive filter paper system was successfully prepared with RT4 as on-site assay kit. • Long-term MTT assay conducted showed low cytotoxicity of RT4 in living cells. • Cell imaging studies showed permeability of RT4 in detecting intracellular Fe3+. A new fluorescent sensor, RT4 has been synthesized by reacting trans -4-(diethylamino)cinnamaldehyde with rhodamine B hydrazide in a one-step reaction. The characterization of RT4 was done by using FT-IR, 1H NMR, 13C NMR, and single crystal X-ray crystallography. In aqueous acetonitrile (1:1, v/v pH 7.5), RT4 exhibited a highly selective and sensitive colorimetric response upon recognition of Cu2+ and fluorometric response with Fe3+ ions. The calculated limit of detections (LOD) of RT4 with Cu2+ and Fe3+ were 0.20 and 0.18 µM at λ abs/em = 555 and 585 nm, respectively. Test strips for colorimetric detection of Cu2+ and Fe3+ as an on-site test kit were successfully prepared. Furthermore, the MTT assay indicated that RT4 possess low cytotoxicity in human colorectal carcinoma HCT 116 after 24 h. The fluorescence microscopy experiment suggested that RT4 could also serve as a biological fluorescence probe for the detection of Fe3+in HCT 116 cells. [ABSTRACT FROM AUTHOR]

A novel indazole fused rhodamine fluorescent dye with large Stokes shift and stable fluorescence in water for constructing an Hg2+-selective probe and cell imaging applications. [Display omitted] • A indazole fused rhodamine dye InRh has been prepared with stable fluroescence in water. • Probe InRhH can respond to Hg2+ with high selectivity and sensitivity by fluorescence and absorption spectra. • Probe InRhH shows promising application in tracing Hg2+ in living cells. Developing selective and sensitive probes for mercury ion (Hg2+) is of great significance because Hg2+ exhibits high toxicity and poses a potential threat to public health and the environment. Herein, a newly designed indazole fused rhodamine dye InRh has been prepared, which shows stable fluorescent signals in water at a wide pH range of 1.0–10.0. Based on the dye InRh, a novel fluorescent probe InRhH for Hg2+ is further developed by modifying the spirolactone ring of InRh to form a closed spirolactam ring. The probe shows selective fluorescence "off–on" signal changes to Hg2+ with a visible color change and response time of 40 min in H 2 O/CH 3 CN (pH = 6.0, v/v = 4/1), and the detection limit for Hg2+ is measured to be 0.33 nM. The recognition mechanism for Hg2+ can be ascribed to the binding interactions between Hg2+ and probe in a 2: 1 coordination mode, which promotes the occurrence of spirolactam ring opening and further hydrolysis. In addition, the InRhH can be applied for test strip experiments and tracing 10−6 M level Hg2+ with visible color change. Furthermore, the suitable cytotoxicity allows the probe to apply for sensing Hg2+ in living HeLa cells by fluorescence imaging. [ABSTRACT FROM AUTHOR]

• A colorimetric and ratiometric fluorescent probe for highly selective recognition of Hg2+ was synthesized. • The probe could detect Hg2+ in living cells. • The emission peak red shifted 109 nm upon addition of Hg2+. Although fluorescent probes had become powerful tools to detect and image mercury ion (Hg2+), most of them suffered from a single signal change. Therefore, a new ratiometric fluorescent probe 1, with a quinoline–benzothiazole group as donor and a rhodamine as acceptor, was constructed for Hg2+ detection in this paper study. Results showed that Probe 1 was highly sensitive and selective to Hg2+, with a linear range of 0–26 μM and a detection limit (LOD) of 0.2 μM. Moreover, with excess competitive metal ions in DMF–H 2 O (v/v, 7/3), probe 1 exhibited excellent colorimetric selectivity and sensitivity to Hg2+ with the significant color change from colorless to pink with a linear range 0–28 μM and a LOD of 0.37 μM, because Hg2+ promoted the rhodamine hydrazide opening. And probe 1 finally was used to detect Hg2+ in living cells. [ABSTRACT FROM AUTHOR]