Cancellation of Contact Quenching : A Simple Concept for Selective Chemosensing of Basic Fluoride and Acetate Anions

A weakly fluorescent acid-base pair formed by reacting fluorescent acridine orange with the quencher picric acid is reported for the detection of basic fluoride and acetate anions. Deprotonation by these anions causes disengagement of the fluorescent acridine orange from the quencher, picric acid. This phenomenon cancels the quenching existing in the native probe, thereby allowing for the optical signalling of fluoride and acetate anions by color modulation as well fluorescence switch-on response. Anions such as Br-, I-, Cl-, NO3-, SCN-, HSO4-, and H2PO4- offer no detectable interferences even in excess concentrations

Novel bipolar diaryloxadiazole-benzofuran conjugates: Synthesis, optical, electrochemical and thermal studies

368-373<span style="font-size:9.0pt;mso-bidi-font-size: 8.0pt;font-family:" times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-US">A series of diaryloxadiazole chromophores incorporating benzofuran rings of varying donor characters has been readily synthesized in a one step protocol. These donor-acceptor-donor systems, designated as <b style="mso-bidi-font-weight: normal">Benzmox-1-4 exhibit positive solvatochromic behavior and thermal stabilities in excess of 300°C. From cyclic voltammetry and emission band data, the HOMO and LUMO energies of Benzmox-1-4 have been calculated to be in the range of 6.43 to 5.65 eV and 2.96 to 3.29 eV, respectively. Of the four chromophoric systems studied, Benzmox-2 and<span style="mso-bidi-font-weight: bold"> Benzmox-3 display band gaps of 3.22 and 3.16 eV, and high luminescence efficiency of 0.34 and 0.55, respectively. These features make Benzmox-2 and<b style="mso-bidi-font-weight: normal"> Benzmox-3 promising bipolar blue light emitting host materials.</span

Synthesis of new donor-acceptor thiophene linked coumarin chromophores: Potential photosensitizers for dye sensitized solar cells

799-804Synthesis of four new dyes, designated as C1-C4, incorporating dialkylamino coumarin as a donor, thiophene ring as a common spacer and quinazolinone-N-acetic acid, homophthalimide-N-acetic acid, rhodanine acetic acid and indoline carboxylic acid as acceptors, respectively is reported. Condensation of 4-diethylaminosalicaldehyde with thiophene-2-acetic acid methyl ester afforded 3-(2-thiophenyl) coumarin 3, which has been formylated to afford aldehyde 4. Knoevenagel condensation of 4 with four different acceptors affords C1-C4. The dyes show absorption maxima in the range of 497 to 538 nm and high extinction coefficients in the range of 32700 to 54300 M−1cm−1. The band gaps of C1-C4, derived from the absorption cut-off edges are estimated to be 2.21, 2.27, 2.09 and 2.00 eV respectively. High extinction coefficients coupled with narrow band gaps are promising features of these dyes which may allow them to act as photosensitizers in dye sensitized solar cells

Cancellation of contact quenching: A simple concept for selective chemosensing of basic fluoride and acetate anions

1164-1168A weakly fluorescent acid-base pair formed by reacting fluorescent acridine orange with the quencher picric acid is reported for the detection of basic fluoride and acetate anions. Deprotonation by these anions causes disengagement of the fluorescent acridine orange from the quencher, picric acid. This phenomenon cancels the quenching existing in the native probe, thereby allowing for the optical signalling of fluoride and acetate anions by colour modulation as well as fluorescence switch-on response. Anions such as Br, I, Cl, NO3, SCN, HSO4, and H2PO4 offer no detectable interference even when in excess concentration

A new benzimidazolium incorporated chemodosimeter affording dual chromogenic and fluorescence switch-on signaling for the selective targeting of cyanide

[eng] We have designed and synthesized a new chemodosimeter, Benzolin-A, which selectively responds to toxic cyanide by dual colorimetric and fluorescence turnon responses in buffered aqueous DMSO. In the presence of cyanide, we observe absorbance red shift of 108 nm (color changing from colorless to yellow) and fivefold fluorescence enhancement. The 1H NMR studies confirm the nucleophilic addition mechanism, and consistent with the experimental findings, the computational work predicts the feasibility of photoelectron transfer or energy transfer process in the native probe, as well as enhanced internal charge transfer in the Benzolin-A-cyanide adduct. Noteworthily, several background anions, such as F-, Cl-, AcO-, SCN-, HSO4 -, NO3 -, Br-, I- and H2PO4 - exhibit none or insignificant optical perturbations

A simple and efficient dual optical signaling chemodosimeter for toxic Hg(II)

10-Methylthioacridone, designated as acrithion, has been employed as an easily accessible chemodosimeter for the optical targeting of toxic Hg2+ in buffered aqueous DMSO. The Hg2+-mediated desulfurization of the probe is translated into selective dual signaling of Hg2+ by means of color bleaching and fluorescence amplification while several other metal ions, including potentially competing Ag+, Cu2+ and Pb2+, afford no significant interferences even in excess concentrations