A novel calix[4]arene fluorescent receptor for selective recognition of acetate anion

A novel bridged fluorescent calix[4]arene with 1,8-diaminoanthracene and glycine at the upper rim has been prepared, which exhibited selective recognition towards AcO⁻ over other anions such as F⁻, Cl⁻, Br⁻, , , I⁻ and by fluorescence spectroscopy and ¹H NMR method.     

Design of steroid-based imidazolium receptors for fluoride ion recognition

New deoxycholic acid-based cyclic receptors bearing imidazolium and benzimidazolium moieties bridged with o-xylelene and 1,8-dimethylenenaphthalene groups have been synthesized. Anion binding studies using ¹H NMR revealed that receptors having naphthalenic group as spacer exhibit very high selectivity for fluoride ion over other anions while receptors with o-xylelene group show a preference for the chloride ion.     

A high selective anion colorimetric sensor based on salicylaldehyde for fluoride in aqueous media

A new and simple salicylaldehyde-based sensor 1 designed for fluoride sensing has been investigated in DMSO and even in the 9/1 DMSO/H₂O (v/v) mixtures. The affinity constants of receptor 1 for anionic species in the 9/1 DMSO/H₂O (v/v) reveal that it is sensitive to F. Also, the color changes induced by anions can provide a way of detection by ‘naked-eye’. These result can be substantiated by the spectrum changes upon the addition of 25 equiv. anions to 1 in the 9/1 DMSO/H₂O solution. The further insights to the nature of interactions between the sensor 1 and F⁻ were investigated by ¹H NMR titration experiments in 9/1 DMSO-d₆/H₂O (v/v). In addition, the proposed binding mode between 1 and F⁻ was suggested.     

Development of aryl-containing dipyrrolyldiketone difluoroboron complexes (BONEPYs): Tune the hydrogen bond o–CH···F for fluoride recognition

Dipyrrolyldiketone difluoroboron complexes (BONEPYs) were synthesized by condensation of the corresponding pyrroles and malonyl chloride followed by treatment with BF₃·OEt₂. The aryl-substituted pyrrole is introduced to form a cyclic system in order to investigate anion binding studies. In BONEPYs 1–3 the o-H of the aryl group forms hydrogen bonding with F⁻ to give a more table complex. In contrast, the intramolecular hydrogen-bonded BONEPY endo-4 is more stable than its exo isomer. While adding F⁻, the hydrogen bonds must be broken first to give 4·(3)F⁻. Owing to the electron-rich group (-OMe), the o-H of the phenyl group can hardly interact with F⁻ via hydrogen bonding to give the less stable complex 4·(5)F⁻. The energy differences between the different conformations were calculated using DFT methods, which is consistent to the experimental observations.     

A novel anthracene-based receptor: Highly sensitive fluorescent and colorimetric receptor for fluoride

A new highly sensitive colorimetric receptor 1 for fluoride based on anthracene-9,10-dicarbaldehyde bis-p-nitrophenylhydrazone was designed, synthesized and characterized. Experiments showed that the receptor 1 can selectively recognize the fluoride in DMSO and even in 95/5 DMSO/H₂O (v/v) mixtures. The ability of recognition and the bond between receptor 1 and anions were determined using visual inspection, UV-vis and fluorescence analyses. In addition, ¹H NMR experiments were carried out to explore the nature of interaction between receptor 1 and fluoride. Finally, analytical application and detection of fluoride in toothpaste have been studied.     

Highly selective fluorescence turn-on determination of fluoride ions via chromogenic aggregation of a silyloxy-functionalized salicylaldehyde azine

A novel fluorescent chemsensor TBS-protected salicylaldehyde azine (TSAA) for fluoride ion was developed based on aggregation-induced emission (AIE). The probe TSAA was prepared by the reaction of salicylaldehyde azine (SAA) with tert-butyldimethylsilyl chloride (TBS-Cl) via an unusual synthetic methodology and shows only non-emission. Upon treatment with fluoride in aqueous MeCN solution, the TBS protective group of probe TSAA was removed readily and the fluorescence of the probe was switched on, which resulted in a new fluorescence peak around 543 nm. The fluorescent intensity at 543 nm increases linearly with fluoride ion concentration in the range 1–50 μmol L^?1. This proposed probe shows excellent selectivity toward fluoride ion over other common anions and cations.     

A tetra-sulfonamide derivative bearing two dansyl groups designed as a new fluoride selective fluorescent chemosensor

A new fluorescent chemosensor based on an acyclic tetra-sulfonamide derivative linked to two dansyl groups has been conveniently synthesized. Its high selective binding ability to fluoride ions over other halide ions was demonstrated by using fluorescence as well as ¹H NMR spectra.     

A thiocyanate-based hybrid molecular salt as a new fluorescent chemosensor for fluoride

An organic–inorganic hybrid solid [(dpaH)⁺(NCS)^?] (1) (dpa?=?2,2′-dipyridylamine) based on an anionic template NCS^? has been synthesized. Single crystal X-ray structural analysis reveals that NCS^? templates assemble dpaH⁺ units into a 3-D layer structure along the b axis through strong hydrogen bonding. Molecular salt 1 works as an anion-binder efficiently and selectively for recognition and sensing purposes in aprotic solvents. This receptor shows changes both in its UV-Vis absorption and fluorescence emission spectra upon the addition of F^?, resulting in high selectivity for fluoride detection in CH₃CN. It is promising to use these systems in various sensing applications.     

Capillary electrophoresis with contactless conductivity detection for the quantification of fluoride in lithium ion battery electrolytes and in ionic liquids—A comparison to the results gained with a fluoride ion‐selective electrode

In this study, an optimized method using capillary electrophoresis (CE) with a direct contactless conductivity detector (C⁴D) for a new application field is presented for the quantification of fluoride in common used lithium ion battery (LIB) electrolyte using LiPF₆ in organic carbonate solvents and in ionic liquids (ILs) after contacted to Li metal. The method development for finding the right buffer and the suitable CE conditions for the quantification of fluoride was investigated. The results of the concentration of fluoride in different LIB electrolyte samples were compared to the results from the ion‐selective electrode (ISE). The relative standard deviations (RSDs) and recovery rates for fluoride were obtained with a very high accuracy in both methods. The results of the fluoride concentration in the LIB electrolytes were in very good agreement for both methods. In addition, the limit of detection (LOD) and limit of quantification (LOQ) values were determined for the CE method. The CE method has been applied also for the quantification of fluoride in ILs. In the fresh IL sample, the concentration of fluoride was under the LOD. Another sample of the IL mixed with Li metal has been investigated as well. It was possible to quantify the fluoride concentration in this sample.     

An exclusive fluoride receptor: fluoride-induced proton transfer to a quinoline-based thiourea

A new quinoline-based tripodal thiourea has been synthesized, which exclusively binds fluoride anion in DMSO, showing no affinity for other anions including chloride, bromide, iodide, perchlorate, nitrate, and hydrogen sulfate. As investigated by ¹H NMR, the receptor forms both 1:1 and 1:2 complexes yielding binding constants of 2.32(3) (in log β₁) and 4.39(4) (in log β₂), respectively. The quinoline groups are protonated by fluoride-induced proton transfer from the solution to the host molecule. The 1:2 binding is due to the interactions of one fluoride with NH binding sites of urea sites and another fluoride with secondary ⁺NH binding sites within the tripodal pocket. The formation of both 1:1 and 1:2 complexes has been confirmed by theoretical calculations based on density functional theory (DFT).     

3-Urea-1,8-naphthalimides are good chemosensors: a highly selective dual colorimetric and fluorescent ICT based anion sensor for fluoride

The 1,8-naphthalimide sensor 1 was developed as a colorimetric and fluorescent sensor for anions. Being the first example of such anion sensors, where the 3-position of the naphthalimide ring is used to incorporate the anion recognition moiety, in this case a trifluromethyl derived aryl urea moiety, the sensors gave rise to significant changes in both the absorption and the emission spectra, which were both red shifted upon interacting with anions. The changes were most pronounced for fluoride, and to a lesser extent for acetate and hydrogen phosphate, in DMSO, making 1 a highly selective sensor for F⁻.     

A highly emissive cruciform triarylborane as a ratiometric and solid state fluorescence sensor for fluoride ions

We disclosed a novel cruciform tri-coordinate organoboron compound, 2′,5′-bis{[(4-dimesitylboryl)phenyl]ethynyl}-1′,4′-bis[(4-N,N-diphenylamino)phenyl]-[1,1′:4′,1′]terphenyls, which displays a characteristic intramolecular charge transfer transition and is highly emissive both in solutions and solid state. The complexation with fluoride ions induces a large blue shift in fluorescence, enabling ratiometric fluorescence sensing of fluoride. In addition, its prompt response to fluoride ions was also observed even in the solid state.     

Theoretical study of hydrogen bonded clusters of water and cyanic acid: Hydrogen bonding in terms of the molecular structure

Ab initio and density functional calculations were used to analyze the interaction between a molecule of cyanic acid (HOCN) and up to 4 molecules of water at the B3LYP/6-311++G(d,p) and MP2/6-311++G(d,p) computational levels. The cooperative effect (CE) is increased with the increasing size of the studied clusters. Red shifts of the H–O stretching frequency for complexes involving HOCN as an H-donor were predicted. The strength of the hydrogen bonds in terms of molecular structures could be deduced from a comparison of HOCN–H₂O with HCNO–H₂O, HONC–H₂O and HNCO–H₂O HB clusters. The atom in molecules (AIM) method was used to analyze the cooperative effects on topological parameters.     

TTFV molecular tweezers with phenylboronic acid and phenylboronate endgroups: modular synthesis and electrochemical responses to saccharides and fluoride ion

Tweezer-like molecular systems containing a redox-active tetrathiafulvalene vinylogue (TTFV) unit and two phenylboronate or phenylboronic acid endgroups were synthesized via the Cu-catalyzed alkyne azide coupling (i.e., click) reaction. The TTFV-phenylboronic acid derivative was found to show different differential pulse voltammetric (DPV) responses to various monosaccharides in aqueous DMSO at pH 7.41, suggesting potential use in electrochemical sensing of saccharides. Moreover, the TTFV-phenylboronate derivative exhibited strong binding to the fluoride ion, giving rise to sensitive electrochemical detection of the fluoride ion.     

Cu(II) complex of a flexible tripodal receptor as a highly selective fluorescent probe for iodide

A Cu(II) complex of a tripodal receptor bearing an anthracene moiety on one pod as a fluorophore was synthesized. The anion recognition behavior of the Cu(II) complex was evaluated in CH₃CN/H₂O (95:5, v/v), resulting in an extremely high selectivity for iodide over other anions such as F⁻, Cl⁻, Br⁻, , CH₃COO⁻, and . The Cu(II) complex acts as a selective probe for estimating iodide even in the presence of other anions without any interference.     

A two-dimensional microporous metal–organic framework for highly selective adsorption of carbon dioxide and acetylene

Solvothermal reaction of 3-aminoisonicotinic acid(Haina) and Cu(NO_3)_2·2.5H_2O gave a novel twodimensional(2D) microporous metal–organic framework, [Cu(aina)_2(DMF)]·DMF(1, DMF = N,N-dimethylformamide). Single-crystal X-ray crystallographic study of compound 1 revealed that Cu(II)ions are linked by ainaàligands forming square grid-like layers, which stack together via multiple hydrogen bonding interactions. The solvent-free framework of 1a displayed considerable porosity(void = 46.5%) with one-dimensional(1D) open channels(4.7 ? ? 4.8 ?) functionalized by amino groups.Gas sorption measurements of 1 revealed selective carbon dioxide(CO_2) and acetylene(C_2H_2) adsorption over methane(CH_4) and nitrogen(N_2) at ambient temperature.     

Design and synthesis of an ortho-phenylenediamine-based open cleft: a selective fluorescent chemosensor for dihydrogen phosphate

A new ortho-phenylenediamine-based fluorescent cleft 1 has been designed and synthesized. The open cleft of 1 selectively recognizes tetrabutylammonium dihydrogen phosphate in CH₃CN by exhibiting a significant decrease in the emission of anthracene. The interactions of 1 are also investigated in aq CH₃OH where no measurable change in the emission is observed for tetrabutylammonium dihydrogen phosphate, although sodium salts of phosphate, hydrogen phosphate, and dihydrogen phosphate exhibit moderate changes. Tetrabutylammonium hydrogen sulfate is sensed effectively in aq CH₃OH. The anion binding properties of 1 were evaluated by ¹H NMR, UV-vis, and fluorescence spectroscopic methods.