Fluorescence Chemosensor

A rarely observed example of post-synthetically increasing pore space, while retaining the chemical functionality of the original metal-organic framework is reported. Conventional solvothermal heating in air was used to effect an efficient post-synthetic rearrangement of a bisallyloxy-tagged zinc metal-organic framework. This leads to the pore-space expanded MOF displaying a higher surface area yet lower affinity for CO2 sorption compared to the original MOF.

The complex of Al (111) with paracetamol have synthesized and characterized using UV-Vis, Infrared spectroscopies and melting point. The ligand has been found to behave as tridentate chelating agents. Paracetamol complex coordinate through the carboxylate oxygen, phenolate oxygen atom, and amine group. The complex solubility was evaluated for several solvents and it was found the compound was more soluble in DMSO. Job's method of continuous variation suggested 1 : 2 metals to ligand stoichiometry for paracetamol complex

A two-dimensional (2D) supramolecular organic framework (SOF) has been constructed through the co-assembly of a triphenylamine-based building block and cucurbit[8]uril (CB[8]). Fluorescence turn-on of the non-emissive building block was observed upon the formation of the 2D SOF, which displayed highly selective and sensitive recognition of picric acid over a variety of nitroaromatics.

Dental enamel, an avascular, irreparable, outermost and protective layer of the human clinical crown has a potential to withstand the physico-chemical effects and forces. These properties are being regulated by a unique association among elements occurring in the crystallites setup of human dental enamel. Calcium and phosphate are the major components (hydroxyapatite) in addition to some trace elements which have a profound effect on enamel. The current review was planned to determine the aptitude of various trace elements to substitute and their influence on human dental enamel in terms of physical and chemical properties.

Selective and sensitive solid sensory substrates for detecting Al(III) in pure water are reported. The material is a flexible polymer film that can be handled and exhibits gel behavior and membrane performance. The film features a chemically anchored salicylaldehyde benzoylhydrazone derivative as an aluminum ion fluorescence sensor. A novel procedure for measuring Al(III) at the ppb level using a single solution drop in 20 min was developed. In this procedure, a drop was allowed to enter the hydrophilic material for 15 min before a 5 min drying period. The process forced the Al(III) to interact with the sensory motifs within the membrane before measuring the fluorescence of the system. The limit of detection of Al(III) was 22 ppm. Furthermore, a water-soluble sensory polymer containing the same sensory motifs was developed with a limit of detection of Al(III) of 1.5 ppb, which was significantly lower than the Environmental Protection Agency recommendations for drinking water.

For efficiently measuring copper (II) ions in the acidic media of white wine, a new chemosensor based on rhodamine B coupled to a tetraazamacrocyclic ring (13aneN4CH2NH2) was designed and synthesized by a one-pot reaction using ethanol as a green solvent. The obtained chemosensor was characterized via NMR, UV and fluorescent spectra. It was marked with no color emission under neutral pH conditions, with a pink color emission under acidic conditions, and a magenta color emission under acidic conditions where copper (II) ions were present. The sensitivity towards copper (II) ions was tested and verified over Ca2+, Ag+, Zn2+, Mg2+, Co2+, Ni2+, Fe2+, Pb2+, Cd2+, Fe3+, and Mn2+, with a detection limit of 4.38 × 10−8 M in the fluorescence spectrum.

The sensing properties of naphthaldimine-glucofuranose conjugates 1 and 2 towards metal ions were investigated by 1H NMR titration, FTIR, absorbance, and fluorescence spectroscopic methods. The absorbance and fluorescence studies indicated that compound 1 formed coordination with Fe2+ and Cu2+ ions in DMSO through color changes yellow to brown and colorless, respectively. The Job's plots using absorbance data showed metal-ligand binding ratio is 1:1 for both cases. The formation of 1-Fe2+ and 1-Cu2+ complexes have been analyzed by absorption and emission spectroscopy, high-resolution mass spectrometry (HRMS) data, FTIR, 1H NMR titration experiment, and DFT calculations. The detection limits of naphthaldimine sugar conjugate 1 towards Fe2+/Cu2+ were calculated from UV-vis and fluorescence data according to the standard method. The sugar-naphthaldimine conjugate 2 has been used to establish the binding mode of 1 with Fe2+ or Cu2+ ions in DMSO.

A simple (R)-(À)-2-phenylglycinol functionalized Schiff base exhibited a dual response to Zn 2+ , Cu 2+ and Fe 2+ ions in water:methanol, (90:10 v/v). The compound displays an ''off-on'' fluorescent effect with Zn 2+ ions. The emission response decreased with Cu 2+ forming a Cu 2+ /Zn 2+ specie. The fluorescence signal is restored upon addition of sulfide anion (S 2À) using the Cu 2+ displacement approach, forming again the Zinc complex. Additionally, the sensor exhibits a second channel (colorimetric) response with Fe 2+ even in the presence of competing Fe 3+ ions. The pH profiles allowed to determine the pK a values and the pHdependent change in the sensor recognition process. In addition, TD-DFT quantum chemical calculations were implemented to analyze the sensing mechanism by means of Natural Transition Orbital (NTO) analysis. Flow cytometry experiments demonstrated that the sensor successfully detects either exogenous or endogenous (natural) Zn 2+ ions in Jurkat cells with high sensitivity.

A suite of two new tetraruthenium metallarectangles 5 and 6 have been obtained from [2 + 2] selfassemblies between dipyridylethynyltriptycene 2 and one of the two dinuclear arene ruthenium clips, [Ru 2 (μ-η 4-OO∩OO) (η 6-p-cymene) 2 ][OTf] 2 ; (OO∩OO = oxalate 3; 6,11-dihydroxy-5,12naphthacenedionato (dotq) 4; OTf = triflate). These molecular rectangles are fully characterized by 1 H NMR spectroscopy, electrospray mass spectrometry. A single crystal of 6 was suitable for X-ray diffraction structural characterization. These new metallarectangles showed fluorescence behavior in solution, have been examined for emission quenching effects with various aromatic compounds, and show high quenching selectivity and sensitivity towards nitroaromatics, particularly picric acid and trinitrotoluene. Excited-state charge transfer from the rectangles to nitro aromatic substrates can be used to develop selective fluorescent sensors for nitro aromatics.

Pyrene-appended β-cyclodextrin based multi-responsive self-assembled nanoaggregates allowed guest specific distinctive detection of pirimicarb, TNT, TNB and picric acid. Highlights:  A pyrene-appended cyclodextrin probe was synthesized in a highly efficient manner  The fluorescent probe self-assembles into nanoaggregates in water  The nanoaggregates are stimuli-responsive  The nanoaggregates show guest specific distinctive detection of pirimicarb and trinitroexplosives

We designed new fluorescent chemical sensors for Fe 3+ ion detection, by conjugating amino acids as receptors into an anthracene fluorophore. The conjugates were synthesized in solid phase by Fmocchemistry. Fluorescence sensors containing Asp (1) and Glu (2) both had exclusive selectivity for Fe 3+ in 100% aqueous solution and in a mixed organic-aqueous solvent system. Other metal ions did not interfere with the detection ability of the sensors for Fe 3+. The sensors detect Fe 3+ ions via a chelationenhanced fluorescent quenching effect. The binding affinity, reversible monitoring, and pH sensitivity of the sensors were investigated. In addition, detection of fluoride ion among halide ions was done by a chemosensing ensemble method with 1-Fe 3+ and 2-Fe 3+ complexes.

A novel multiple amide based Schiff base chemosensor L has been designed rationally for selective colorimetric detection of Cu 2+ ion in CH 3 OHeH 2 O (1:1 v/v, tris HCl buffer 10 µM, pH = 7.2) solution. The colour change (colourless to yellow) is so prominent to be visible in bare eye. From the absorption titration, job's plot measurement and ESI-MS revealed that receptor-analyte binding occurs in a 2:1 fashion and the binding sites were confirmed by the X-ray single crystal structure of host-guest complex. Solvent dependent crystal structure from a homoleptic monomer to 2D polymer was observed. The detection limit was found to be 1.8 µM with the association constant value 1.3 × 10 2 M −1/2 which is highly desirable for 2:1 complexes. The chemosensor L has been applied for construction of binary logical device, recovery of contaminated water samples and smart-phone based analysis.

A benzothiazolium-derived colorimetric and fluorescent chemosensor (L) for detection of mercury ions has been prepared. The detection limits of the colorimetric and fluorescent method for mercury ions are 15.3 and 11.8 ppb, respectively, much lower than the reported chemosensors based on similar derivatives of benzothiazolium. The optimized molecular structures, absorption and fluorescence characteristics of the chemosensor and its complex with mercury ions were carried out using the calculations at the B3LYP/LanL2DZ level of theory, combination with Atoms in Molecules and Natural Bond Orbitals analyses.

A series of protected and terminal dialkynes with extended -conjugation through a condensed aromatic linker unit in the backbone, 1,4-bis(trimethylsilylethynyl)naphthalene, 2a, 1,4-bis(ethynyl)naphthalene, 2b, 9,10-bis(trimethylsilylethynyl)anthracene 3a, 9,10-bis(ethynyl)anthracene 3b, have been synthesized and characterized spectroscopically. The solid-state structures of 2a and 3a have been confirmed by single crystal X-ray diffraction studies. Reaction of two equivalents of the complex trans-[Ph(Et 3 P) 2 PtCl] with an equivalent of the terminal dialkynes 1,4-bis(ethynyl)benzene 1b and 2b-3b, in i Pr 2 NH-CH 2 Cl 2 , in the presence of CuI, at room temperature, afforded the platinum(II) di-ynes trans-[Ph(Et 3 P) 2 Pt-CC-R-CC-Pt(PEt 3) 2 Ph] (R = benzene-1,4-diyl 1c; naphthalene-1,4-diyl 2c and anthracene-9,10diyl 3c) while reactions between equimolar quantities of trans-[(n Bu 3 P) 2 PtCl 2 ] and 2b-3b under similar conditions readily afforded the platinum(II) poly-ynes trans-[-(n Bu 3 P) 2 Pt-CC-R-CC-] n (R = naphthalene-1,4-diyl 2d and anthracene-9,10-diyl 3d). The Pt(II) diynes and poly-ynes have been characterized by analytical and spectroscopic methods, and the single crystal X-ray structures of 1c and 2c have been determined. These structures confirm the trans-square planar geometry at the platinum centres and the linear nature of the molecules. The di-ynes and poly-ynes are soluble in organic solvents and readily cast into thin films. Optical spectroscopic measurements reveal that the electron-rich naphthalene and anthracene spacers create strong donor-acceptor interactions between the Pt(II) centres and conjugated ligands along the rigid backbone of the organometallic polymers. Thermogravimetry shows that the di-ynes possess a somewhat higher thermal stability than the corresponding poly-ynes. Both the Pt(II) di-ynes and the poly-ynes exhibit increasing thermal stability along the series of spacers from phenylene through naphthalene to anthracene.

 Highlights  A fluorescent and colorimetric sensor exhibits a specific recognition for an explosive chemical: 2,4,6-trinitrophenol or picric acid.  The chemical sensor provides both fluorescence enhancement and quenching by simply switching the solvents.  Chromogenic change is observed from colorless to yellow, serving as a "nakedeye" indicator. 2  Two different types of crystal structures are successfully recrystallized to confirm highly interactive affinity of the host-guest molecules.

Two thio-urea based bifunctional probes (H2L 1-S and H2L 2-S) have been designed and fabricated for the colorimetric and fluorometric detection of mercury(II) and acetate ions respectively in DMSO media. Both the H2L 1-S and H2L 2-S were fully characterized by various spectroscopic techniques and the solid-state structure of H2L 1-S was determined via single-crystal X-ray diffraction. The high sensitivity and selectivity of the probes for Hg 2+ were achieved by the Hg 2+ promoted desulfurization reactions utilizing the high thiophilic nature of mercury and was monitored by UV-vis spectroscopy. Most interestingly the desulfurized product was isolated and characterized by ESI-MS and single crystal X-ray diffraction. The probes H2L 1-S and H2L 2-S were found to be highly selective towards acetate ion (AcO-) in fluorescence channel. These probes showed a distinct fluorescence enhancement only in the presence of AcO − at 493 nm due to the inhibition of photo induced electron transfer (PET). Finally, the cytotoxicity study was carried out for biological application. The probe showed minimum cytotoxicity and was suitable for intracellular acetate ion imaging.