Ratiometric fluorescence-based and chromogenic sensors for the detection of fluoride ions and their application in real samples.

This review focuses on the results of synthetic ratiometric fluorescent and colorimetric probes, which have been applied to qualitatively and quantitatively detect fluoride anions in cells, living organisms, and real samples. Primary attention is given to progress made in the working mechanism and applications of these probes to detect fluoride ions in living systems. In addition, design strategies and detection limit for these probes are discussed.

Tailoring Ligand Environment toward Development of Colorimetric and Fluorescence Indicator for Biological Mn(II) Imaging.

Mn(2+) ion plays an essential role in all forms of life. Paramagnetic nature of Mn(2+) and its close resemblance with Ca(2+) and Mg(2+) are two key limiting factors responsible for the least development of fluorescence probes suitable for bioimaging. In literature we have found only a few Mn(2+) selective fluorescent sensor and their applications.

Hydrazine selective dual signaling chemodosimetric probe in physiological conditions and its application in live cells.

A rhodamine-cyanobenzene conjugate, (E)-4-((2-(3',6'-bis(diethylamino)-3-oxospiro[isoindoline-1,9'-xanthene]-2-yl)ethylimino)methyl)benzonitrile (1), which structure has been elucidated by single crystal X-ray diffraction, was synthesized for selective fluorescent "turn-on" and colorimetric recognition of hydrazine at physiological pH 7.4. It was established that 1 detects hydrazine up to 58 nM.

Interaction of water with a benzimidazole derivative: fluorescence and colorimetric recognition of trace level water involving intra-molecular charge transfer process.

Benzimidazole-derived ICT-based probe, DFPBEN is developed for trace level determination of water. In presence of water, the naked eye color of DFPBEN changes from red to yellow, while it turns to green from red under UV light. Upon addition of water, DFPBEN shows a ratiometric absorbance change in methanol.

Pyridine Based Fluorescence Probe: Simultaneous Detection and Removal of Arsenate from Real Samples with Living Cell Imaging Properties.

Pyridine based fluorescence probe, DFPPIC and its functionalized Merrifield polymer has been synthesized, characterized and used as an arsenate selective fluorescence sensor. Arsenate induced fluorescence enhancement is attributed to inter-molecular H-bonding assisted CHEF process. The detection limit for arsenate is 0.

An INHIBIT logic gate from a thiophene derivative using iron and zinc ions as the input: tuning the efficiency on moving from naphthalene to anthracene to pyrene for the green luminescent detection of the intracellular iron.

A pyrene-thiophene conjugate has been used for the efficient detection of intracellular irons through the generation of bright green luminescence. Amongst three different probes being reported, it is observed that the efficiency for the naked eye green luminescent detection of iron increases on moving from naphthalene to anthracene to pyrene. The developed technique may be very useful to monitor iron and zinc supplementation as single micronutrients in living systems through the construction of an INHIBIT logic gate.

FRET based tri-color emissive rhodamine-pyrene conjugate as an Al3+ selective colorimetric and fluorescence sensor for living cell imaging.

A rhodamine-pyrene hybrid molecule acts as a colorimetric and fluorimetric sensor for Al(3+) through time dependent PET-CHEF and FRET processes associated with tri-color emission. Intracellular Al(3+) has been visualized through time dependent blue-green-red emission. The lowest limit of detection for Al(3+) is 0.

Selective sensing of Hg²⁺ using rhodamine-thiophene conjugate: red light emission and visual detection of intracellular Hg²⁺ at nanomolar level.

Rhodamine-thiophene conjugate (L) has been synthesized and characterized by (1)H NMR, FTIR and mass spectra. L shows a large enhancement in emission intensity in presence of Hg(2+). Moreover, naked eye color of L becomes intense red in presence of Hg(2+).

Fluorescence sensing of arsenate at nanomolar level in a greener way: naphthalene based probe for living cell imaging.

Naphthalene-salisaldehyde conjugate (NAPSAL) is established as a novel arsenate (H2AsO4(-)) selective 'turn-on' fluorescence probe. It can detect as low as 5 × 10(-9) M H2AsO4(-) in HEPES buffered EtOH : water (0.1 M, 1 : 9, v/v, pH 7.

A coumarin-based "turn-on" fluorescent sensor for the determination of Al3+: single crystal X-ray structure and cell staining properties.

An efficient Al(3+) receptor, 6-(2-hydroxybenzylideneamino)-2H-chromen-2-one (HBC), has been synthesized by condensing salicylaldehyde with 6-aminocoumarin. The molecular structure of HBC has been determined by a single crystal X-ray analysis. It was established that in the presence of Al(3+), HBC shows 25 fold enhancement of fluorescence intensity which might be attributed to the chelation-enhanced fluorescence (CHEF) process.

A naphthalene-thiophene hybrid molecule as a fluorescent AND logic gate with Zn2+ and OAc- ions as inputs: cell imaging and computational studies.

A naphthalene-thiophene hybrid molecule (Z)-1-((thiophen-2-ylmethylamino)methylene)naphthalen-2(1H)-one () was prepared by condensation of 2-thiophenemethylamine and 2-hydroxy-1-naphthaldehyde. According to FTIR, (1)H NMR spectrometry and single crystal X-ray analysis, exists in the cis-keto-amine tautomeric form. behaves like a molecular AND type binary logic gate with two inputs viz.

Rhodamine-based fluorescent probe for Al3+ through time-dependent PET-CHEF-FRET processes and its cell staining application.

Rhodamine-diformyl p-cresol conjugate (L) has been developed as a novel Al(3+)-selective fluorometric and colorimetric sensor based on the FRET mechanism for the first time. L can selectively detect Al(3+) through time-dependent PET-CHEF and FRET processes. This phenomenon is nicely reflected from (1)H NMR, fluorescence lifetime, and fluorescence cell imaging studies.

Ratiometric fluorescence sensing and intracellular imaging of Al3+ ions driven by an intramolecular excimer formation of a pyrimidine-pyrene scaffold.

An Al(3+) selective ratiometric fluorescent probe (L) has been synthesized by condensation of 4,5-diaminopyrimidine with 1-pyrenecarboxaldehyde. The structure of L has been confirmed by single crystal X-ray analysis. In the presence of Al(3+), L exhibits a considerable excimer emission at 445 nm along with the decrease of its monomer emission at 368 nm in DMSO-H2O (4 : 1, v/v).

A rhodamine derivative as a "lock" and SCN- as a "key": visible light excitable SCN- sensing in living cells.

A visible light excitable rhodamine based probe operates as a SCN(-) selective fluorescent "turn-on" sensor for living cell imaging with a detection limit of 0.01 μM, which is much lower than the normal SCN(-) level in the human body. A "lock" and "key" model has been proposed to explain the fluorescence enhancement of the rhodamine probe in the presence of SCN(-).

Antipyrine based arsenate selective fluorescent probe for living cell imaging.

Condensation of salicylaldehyde and 4-aminoantipyrine has yielded a new fluorescent probe (APSAL) capable of detecting intracellular arsenate at the micromolar level for the first time. The structure of the probe has been established by different spectroscopic techniques and confirmed from X-ray crystallography. Common anions, viz.

Cd(II)-triggered excimer-monomer conversion of a pyrene derivative: time dependent red-shift of monomer emission with cell staining application.

An efficient fluorescent probe (E)-N1-((E)-2-((pyren-7-yl)methyleneamino)ethyl)-N2-((pyren-7-yl)methylene)ethane-1,2-diamine (L) has been synthesized by a facile one-step condensation reaction. L can selectively detect Cd(2+) in presence of other common metal ions in 0.1 M HEPES buffered DMSO-water (4 : 1, v/v) medium.

Nickel(II)-induced excimer formation of a naphthalene-based fluorescent probe for living cell imaging.

Ni(2+)-induced intramolecular excimer formation of a naphthalene-based novel fluorescent probe, 1-[(naphthalen-3-yl)methylthio]-2-[(naphthalen-6-yl)methylthio]ethane (L), has been investigated for the first time and nicely demonstrated by excitation spectra, a fluorescence lifetime experiment, and (1)H NMR titration. The addition of Ni(2+) to a solution of L (DMSO:water = 1:1, v/v; λ(em) = 345 nm, λ(ex) = 280 nm) quenched its monomer emission, with subsequent enhancement of the excimer intensity (at 430 nm) with an isoemissive point at 381 nm. The fluorescence lifetime of free L (0.

A naphthalene exciplex based Al3+ selective on-type fluorescent probe for living cells at the physiological pH range: experimental and computational studies.

2-((Naphthalen-6-yl)methylthio)ethanol (HL) was prepared by one pot synthesis using 2-mercaptoethanol and 2-bromomethylnaphthalene. It was found to be a highly selective fluorescent sensor for Al(3+) in the physiological pH (pH 7.0-8.

Thiophene anchored coumarin derivative as a turn-on fluorescent probe for Cr3+: cell imaging and speciation studies.

A thiophene-coumarin hybrid molecule, (6E)-6-((thiophen-2-yl)methyleneamino)-2H-chromen-2-one (TMC) has been prepared and its single crystal X-ray structure is reported. TMC can selectively detect Cr(3+) in presence of other common cations. Both TMC and its Cr(3+) complex are well characterized by different spectroscopic techniques like (1)H NMR, QTOF-MS ES(+), FTIR and elemental analysis as well.

Highly selective organic fluorescent probe for azide ion: formation of a "molecular ring".

An indole based naphthalene derivative is reported as a highly selective fluorescent probe for azide ion in aqueous ethanol. The probe is applied for cell imaging of the N(3)(-) ion in contaminated living cells. Both experimental and theoretical studies have been performed to figure out the plausible mechanism of fluorescence enhancement of the probe upon binding with N(3)(-).

2-(2-Pyridyl) benzimidazole based Co(II) complex as an efficient fluorescent probe for trace level determination of aspartic and glutamic acid in aqueous solution: a displacement approach.

A weakly fluorescent cobalt(II) complex is synthesized using 2-(2-pyridyl)-benzimidazole (PBI) as a chelating fluorescent ligand and characterized by single crystal X-ray structure. This complex serves as an efficient fluorescent probe for trace level determination of aspartic acid (AspA) and glutamic acid (GluA) in aqueous solution. Rest of the naturally occurring amino acids did not interfere.

Identification and interaction of amino acids with leucine-anthracene reagent by TLC and spectrophotometry: experimental and theoretical studies.

A new reagent has been synthesized by coupling anthracene moiety to L-leucine. The reagent is characterized by different analytical techniques. It is capable for easy identification of various amino acids on thin-layer chromatography plates by developing distinguishable colors (detection limit between 0.

A naphthalene-based Al3+ selective fluorescent sensor for living cell imaging.

An efficient fluorescent Al(3+) receptor, N-(2-hydroxy-1-naphthalene)-N'-(2-(2-hydroxy-1-naphthalene)amino-ethyl)-ethane-1,2-diamine (L) has been synthesized by the condensation reaction between 2-hydroxy naphthaldehyde and diethylenetriamine. High selectivity and affinity of L towards Al(3+) in ethanol (EtOH) as well as in HEPES buffer at pH 7.4, makes it suitable to detect intracellular Al(3+) with fluorescence microscopy.

9-Acridone-4-carboxylic acid as an efficient Cr(III) fluorescent sensor: trace level detection, estimation and speciation studies.

9-Acridone-4-carboxylic acid has been established as an efficient Cr(III) fluorescent sensor. The binding of this ligand with Cr(III) is confirmed by FTIR, thermal and mass spectral analysis of the product. Based on this chelation assisted fluorescence quenching, a highly sensitive spectrofluorometric method is developed for trace level detection, estimation and speciation studies of chromium in DMF-water.

Methionine-pyrene hybrid based fluorescent probe for trace level detection and estimation of Hg(II) in aqueous environmental samples: experimental and computational studies.

A new fluorescent, Hg(2+) selective chemosensor, 4-methylsulfanyl-2-[(pyren-4-ylmethylene)-amino] butyric acid methyl ester (L, MP) was synthesized by blending methionine with pyrene. It was well characterized by different analytical techniques, viz. (1)H NMR, (13)C NMR, QTOF mass spectra, elemental analysis, FTIR and UV-vis spectroscopy.