2 research outputs found

    One-Pot Coupling–Coupling–Cyclocondensation Synthesis of Fluorescent Pyrazoles

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    Consecutive four-component coupling–coupling–cyclocondensation syntheses of pyrazoles and pyrimidines were developed by taking advantage of the provisional, sequentially Pd-catalyzed one-pot generation of alkynones from aryl iodides, ethynylmagnesium bromide, and acid chlorides. This one-pot methodology allows the concise, diversity-oriented generation of a set of donor-, acceptor-, and donor–acceptor-substituted pyrazoles, which are interesting fluorophores. Most distinctly, donor–acceptor pyrazoles display remarkably red-shifted emission maxima and pronounced positive solvochromicity, spanning an overall range from 363 nm (cyclohexane) to 595 nm (acetonitrile). DFT and TD-DFT calculations elucidate the electronic structure and the photophysical behavior. Upon photonic excitation, considerable charge-transfer character becomes apparent, which rationalizes the origin of huge Stokes shifts and solvochromic behavior

    Combined UV-Vis-absorbance and Reflectance Spectroscopy Study of Dye Transfer Kinetics in Aqueous Mixtures of Surfactants

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    <div> <div> <div> <p>We report an analytical approach to study the kinetics of desorption and exhaustion of a hydrophobic dye in a multicomponent washing model environment. The process of <b>dye transfer </b>between an acceptor textile (white polyamide), detergent micelles and a donor textile (red polyester) was quantified by a combination of colorimetric analyses.<b> UV-Vis absorbance and UV- reflectance </b>spectroscopy were used to follow the concentration of the solubilised dye in the micelles and the amount of dyer transferred to the acceptor textile, respectively, as a function of time. Up to ≃ 10 min of the washing process, the released dye is predominantly solubilised in surfactant micelles. At later times, the adsorption of the dye on the hydrophobic surface of the acceptor textile is energetically favoured. The shift of the desorption equilibrium in the presence of the acceptor textile results in ≃ 30% increase in the release of the dye. The reported methodology provides insight into the competition between solubilisation of hydrophobic molecules by amphiphiles and dye adsorption on solid substrates, important for designing novel concepts of dye transfer inhibition. </p> </div> </div> </div