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[Display omitted] • We have successfully designed and synthesized a new biocompatible chromo- and fluorogenic probe L2 derived from rhodamine-6G which showed a selective and sensitive colorimetric as well as " turn-ON " fluorescence response towards Fe3+ ion over mono-, di- and other trivalent metal ions. • Complete aqua friendliness of this probe has drawn special attention over other rhodamine 6G based chemosensors. • A large enhancement of fluorescence intensity of L2 (14 fold) in the presence of Fe3+ in aqueous medium (HEPES buffer at pH 7.2) with the development of reddish yellow color clearly indicates that this probe L2 can be used for the detection of Fe3+ through naked eye. • The K f value was evaluated to be (1.16 ± 0.04) x 104 M−1 from the fluorescence titration data at systematic increasing concentration of metal ions and fixed 20 μM concentration of ligand. • The higher values of quantum yields (0.523) for [ L2 -Fe3+] over the free ligand (0.013) indicate the higher stability of the complexes in the excited states. • Job's plot confirms 1:1 stoichiometric ratio for the binding of Fe3+ with L2. • An excellent reversible fluorescence ' OFF-ON " property of L2 has been observed through fluorescence study with the sequential addition of Fe3+ and CN– ions at room temperature which suggests the reusability of this chemosensor. • The detection limit of L2 for Fe3+ was evaluated to be 4.184 μM and this makes the probe usable to quantify the Fe3+ in real water samples. • As the sensing phenomenon is reversible it helps to frame INHIBIT gate and memory devices. A novel rhodamine-6G based biocompatible chromo- and fluorogenic "OFF-ON" sensor L2 , having amide based metal ion receptor, has been synthesized using Michael addition reaction and characterized by IR, NMR and HRMS spectroscopic studies. It exhibits an excellent selectivity and sensitivity towards Fe3+ in aqueous medium over mono- and di-valent and other trivalent metal ions. A 14-fold enhancement of fluorescence intensity was found upon addition of 11.5 equivalent Fe3+ ion into the probe L2 in H 2 O (pH 7.2, 10 mM HEPES buffer) with colour change from colourless to reddish yellow, providing an opportunity for naked eye detection of Fe3+. The corresponding binding constant K f was evaluated to be (1.16 ± 0.04) x 104 M−1 with 1:1 stoichiometry. Quantum yields of L2 and [L2 - Fe3+] complex in H 2 O (pH 7.2, 10 mM HEPES buffer) were found to be 0.013 and 0.523, respectively using Rhodamine-6G as standard. LOD of L2 for Fe3+ detection in aqueous medium determined by 3σ/slope method was found to be 4.184 μM. Cyanide ion scavanges Fe3+ from [L2 - Fe3+] resulting quenching of fluorescence due to re-attainment of the non-fluorescent spirolactam ring form of the probe. As the sensing phenomenon is reversible, it helps to frame INHIBIT logic gate and memory devices. [ABSTRACT FROM AUTHOR]

A new rhodamine 6G-benzylamine-based sensor (L1), having only hydrocarbon skeletons in the extended part, was synthesized and characterized by single-crystal X-ray crystallographic study. It exhibited excellent selective and sensitive recognition of trivalent metal ions M3+ (M = Fe, Al and Cr) over mono- and di-valent and other trivalent metal ions. A large enhancement of the fluorescence intensity for Fe3+ (41-fold), Al3+ (31-fold) and Cr3+ (26-fold) was observed upon the addition of 3.0 equivalent of these metal ions into the probe in H2O/CH3CN (4 : 1, v/v, pH 7.2) with naked eye detection. The corresponding Kf values were evaluated to be 9.4 × 103 M−1 (Fe3+), 1.34 × 104 M−1 (Al3+) and 8.7 × 103 M−1 (Cr3+). Quantum yields of the L1, [L1–Fe3+], [L1–Al3+] and [L1–Cr3+] complexes in H2O/CH3CN (4 : 1, v/v, pH 7.2) were found to be 0.012, 0.489, 0.376 and 0.310, respectively, using rhodamine-6G as standard. LODs for Fe3+, Al3+ and Cr3+ were determined by 3σ methods and found to be 1.28, 1.34 and 2.28 μM, respectively. Cyanide ion scavenged Fe3+ from the [Fe3+–L1] complex and quenched its fluorescence via its ring-closed spirolactam form. Advanced level molecular logic devices using different inputs (2 and 4 inputs) as advanced level logic gates and memory devices were constructed. The large enhancement in fluorescence emission of L1 upon complexation with M3+ metal ions makes the probe suitable for the bio-imaging of M3+ (M = Fe, Al and Cr) in living cells. [ABSTRACT FROM AUTHOR]

A 2-hydroxy-5-methyl-benzene-1,3-dicarboxaldehyde di-oxime based turn-on blue emission fluorescent probe was found to recognize both AsO2− and H2AsO4− in a purely aqueous medium in intra and extra-cellular conditions. Self-organization of the ligand in the absence and presence of AsO2− and H2AsO4− was investigated by DLS, optical microscopy, optical fluorescence microscopy and FE-SEM methods. [ABSTRACT FROM AUTHOR]

A diformyl-p-cresol (DFC)-8-aminoquinoline based dual signaling probe was found to exhibit colorimetric and fluorogenic properties on selective binding towards Mg2+ and Zn2+. Turn-on fluorescent enhancements (FE) as high as 40 fold and 53 fold in 9 : 1 MeCN/water (v/v) at pH 7.2 in HEPES buffer for Mg2+ and Zn2+, respectively, were observed. The binding constants determined from the fluorescence titration data are: K = (1.52 ± 0.21) × 105 M−1 and (9.34 ± 4.0) × 103 M−2 at n = 1 and 0.5, for Mg2+ and Zn2+, respectively. The L : M binding ratios were also determined by Job's method, which support the above findings. This is further substantiated by HRMS analysis. Due to solubility in mixed organo-aqueous solvents as well as cell permeability it could be used for the in vitro/in vivo cell imaging of Mg2+ and Zn2+ ions with no or negligible cytotoxicity. This probe could be made selective towards Mg2+ over Zn2+ in the presence of TPEN, both under intra- and extracellular conditions and is superior to other Mg2+ probes which suffer from selectivity of Mg2+ over Ca2+ or Zn2+. Furthermore the dissociation constant (Kd = 6.60 μM) of the Mg2+-(DFC-8-AQ) complex is far lower than the so far reported Mg2+ probes which fall in the mM range. [ABSTRACT FROM AUTHOR]