Reversible thermochromic systems based on a new library of flavylium spirolactone leuco dyes

The aim of this work was the design, synthesis, and characterization new chromogenic spirolactone dyes based on a 2-phenyl-1-benzopyrylium (flavylium) backbone for further development thermochromic smart labels. influence electron-donating electron-withdrawing groups five synthesized studied in terms color modification, acid-base behavior properties. By using UV–Vis absorption emission spectroscopies, molar absorptivity, oscillator strength, Stokes shift, fluorescence quantum yield were determined each dye to evaluate impact excited state properties designed structures. ability evolve towards leuco species assessed by titrations with triethylamine N,N-diisopropylethylamine non-polar polar aprotic solvents such as acetonitrile octan-1-ol. In addition, reversibility also evaluated protic (water ethanol) Lewis acids (gallic acid iron(III) chloride). number equivalents base/acid required reach product then reverse representing maximum function added content less than 0.01-v/v). Finally, presence long-chain organic amines water-insoluble melting points close room temperature. compounds can switch between two if appropriate conditions are used. Moreover, tests carried out assess their concluded that all display thermochromism some extent. have attached, cyano, stronger effects useful future applications.