Organosilicon compounds as fluorescent chemosensors for fluoride anion recognition

Colorimetric and fluorimetric response of salicylaldehyde dithiosemicarbazone towards fluoride, cyanide and copper ions: Spectroscopic and TD-DFT studies

The sensing mechanism of salicylaldehyde phenyldithiosemicarbazone (SDTSC) chemosensor has been investigated by spectroscopic and TD-DFT methods. The SDTSC shows colourimetric and spectral changes towards fluoride, cyanide and copper ions. The interaction between SDTSC with fluoride, cyanide and copper ions was examined through their absorption and fluorescence behaviour, and found that SDTSC has more sensing ability towards Cu²⁺ ion than CN^- and F^- ions. The ¹H NMR titration with SDTSC and F^- gives the structural changes in the sensing process. The reversibility of SDTSC was also evaluated and thus it is confirmed as a reusable chemosensor which can be clarified by the "Read-Erase-Read-Write" logic system. The DFT and TD-DFT calculations give the detailed sensing mechanism of SDTSC towards fluoride ion. The potential energy surface (PES) analysis confirms the excited state electron transfer mechanism.

Multi-ion detection and molecular switching behaviour of reversible dual fluorescent sensor

The selective chemosensing behaviour of imidazole bisthiocarbohydrazone (IBTC) towards F^- and Cu²⁺ are studied via colorimetric, UV-Visible, fluorescence spectra studies, and binding constants were calculated. The ¹H NMR titration study strongly support that the deprotonation of IBTC followed by the hydrogen bond formation via N1H1 and N2H2 protons with fluoride ion. The fluorescence inactive IBTC-Cu complex became fluorescence active in the presence of perchlorate (ClO₄^-) ion. The selective detection of perchlorate ion was also explained. The F^- sensing mechanism of IBTC has been investigated by Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TDDFT) methods. The theoretical outcomes well reproduce the experimental results. And it concluded the NH protons, nearby the imine group was first captured by the added F^- ion and then deprotonation happened followed by the formation of hydrogen bond. The IBTC found good reversibility character with the alternative addition of Ca²⁺ and F^-. The multi-ion detection of IBTC was used to construct the NOR, OR and INHIBITION molecular logic gates.

Spectral studies on anthracene based dual sensor for Hg2+ and Al3+ ions with two distinct output modes of detection

A simple and easily synthesized colorimetric and fluorescent chemosensor 1, based on aromatic OH and imine moieties as a binding and anthracene as signaling unit, has been synthesized in a one-step procedure. The chemosensor 1 is developed as a dual chemosensor for detection of Hg²⁺ and Al³⁺ ions in CH₃OH, which exhibited a color change from light yellow to dark yellow with Hg²⁺ ions, enabling 1 a suitable "bare eye" indicator for Hg²⁺ ions. On the other hand, fluorescent enhancement with blue shift along with brilliant cyan fluorescence was observed upon binding with Al³⁺ ions. A possible sensing mechanism has been proposed by means of Job's plot and ¹H NMR titration.

A selective emissive chromogenic and fluorogenic seleno-coumarin probe for Cu2+ detection in aprotic media

A new selenium containing coumarin (compound 7) was designed and synthesized from the amide linkage between coumarin-519 (6) and 2-(butylselanyl)ethanamine (5). The molecular structure of 7 was accurately characterized, and its photophysical properties in acetonitrile, ethanol and chloroform solutions were studied by absorption, stationary and time-resolved fluorescence spectroscopies. Changes in the solvent polarity affected the Stokes shift, quantum yields and lifetime of the excited states. The spectroscopic behavior of compound 7 was evaluated in the presence of different monovalent, divalent and trivalent metallic cations (Na⁺, K⁺, Ca²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Hg²⁺, Hg⁺, Ag⁺, Al³⁺, Fe³⁺, Ga³⁺ and Cr³⁺) in acetonitrile solution. Among the tested cations, 7 exhibited high selective interaction with Cu²⁺, which was evidenced by the not expected absorption hypsocromic shift (usually coumarin-519 gives red-shifted complexes) and intense chelation-enhanced fluorescence quenching (CHEQ). We performed spectrophotometric and spectrofluorimetric titrations of 7 upon addition of Cu²⁺. From these data, the minimal detectable and quantifiable amounts were calculated and found to be 0.2 and 0.4 μmol L^-1 by absorption and 0.6 and 1.0 μmol L^-1 by emission, respectively. The 7-Cu²⁺ compound presented the 1 : 1 stoichiometry and the stability constant values of absorption and emission were found to be log β = 5.78 and log β = 6.32 respectively. Taking into account the high selectivity of the 7-Cu²⁺ compound in organic solvent systems, and considering the role of copper in organic transformations, it can be regarded as a promising fluorescent sensor for studies concerning the determination of oxidation-dependent transient entities in organic reactions like those involving cuprates. Additionally, it can be used for the detection and quantification of this metal cation in vitro in aprotic biological systems.

Fluorescent triazolium for sensing fluoride anions in semi-aqueous solution

A new triazolium-based receptor for fluorescent sensing of inorganic fluoride anions in semi-aqueous solution and the solid state was reported.

Multicolorful ratiometric-fluorescent test paper for determination of fluoride ions in environmental water

A ratiometric-fluorescent test paper for the visual detection of the fluoride ion.

C 3v-symmetric anion receptors with guanidine recognition motifs for ratiometric sensing of fluoride

Two new tripodal receptors 3 and 4 derived from a trindane framework having guanidine groups acting as hydrogen bond acceptors are synthesized and characterized for the selective recognition of anions.

Theoretical investigation on the one- and two-photon responsive behavior of fluoride ion probes based on diketopyrrolopyrrole and its π-expanded derivatives

The intrinsic two-photon absorption properties of the studied fluoride anion probes and their corresponding reaction products are systematically investigated.

Spectrometric and kinetics studies involving anionic chromogenic chemodosimeters based on silylated imines in acetonitrile or acetonitrile–water mixtures

The nucleophilic attack of F⁻ or CN⁻ on the silicon center of chemodosimeters, through an S_N2@Si mechanism, released colored phenolates as leaving groups. NMR, PGSE NMR, and UV-vis studies provided evidence on the mechanism of the reactions.

A colorimetric and ratiometric fluorescence sensor for sensitive detection of fluoride ions in water and toothpaste

The colorimetric and ratiometric sensor shows significant spectral response towards fluoride ions in water with a detection limit as low as 2.7 ppb, enabling direct observation with the bare eye as well as quantitative determination of F⁻ in toothpaste.

Pyrene Based Chemosensor for Selective Sensing of Fluoride in Aprotic and Protic Environment

A new aromatic hydrazone based on pyrene-1-aldehyde was synthesized and characterized by (1)H NMR and mass spectrometric analyses. The sensing properties of the hydrazone were studied by absorption and fluorescence studies in the aprotic solvent DMSO. It was capable of visual and fluorescent detection of fluoride over competitive ions (Cl(-), Br(-), H2PO4 (-), AcO(-)). Moreover, the in-situ prepared iron(III) complex of the hydrazone was investigated as a turn off fluorescent fluoride sensor in aqueous medium by displacement mechanism.

Pyridoxal-thiosemicarbazide: its anion sensing ability and application in living cells imaging

A new anion selective chemosensor L was derived through a direct condensation reaction between pyridoxal and thiosemicarbazide.

A sequential logic gate-based “smart probe” for selective monitoring of Cu2+, Fe3+ and CN−/F−via differential analyses

A sequential logic gate-based probe for the detection of Cu²⁺, Fe³⁺, CN⁻ and F⁻ at ppm levels in water.

A fast and selective probe for detection of CN− and F− in water along with a sequential molecular logic circuit via resettable optical readout

A fast and selective probe for detection of CN⁻ and F⁻ at ppm levels in water via multiple readout for precise analysis.