Synthesis and structural determination of fluoran

Thermochromic materials have been widely applied in various civilian sectors, including textiles and healthcare, and hold significant potential for military applications. The prominent characteristic of these materials lies in their reversible color-changing ability in response to temperature variations. Among the compounds containing the xanthene moiety-a functional group commonly found in many dyes and pigments, fluoran stood out due to its high sensitivity in temperature-induced color transitions, particularly when combined with electron acceptors and suitable solvents. In this study, fluoran was synthesized via a two-step reaction involving phthalic anhydride, 3-diethylamino phenol, and p-bromophenol in toluene. The resulting product was a pink solid with a melting point in the range of 171 - 174 °C and a yield of 60,8%. The structure of the synthesized product was confirmed using advanced analytical techniques, including infrared spectroscopy (IR), one-dimensional nuclear magnetic resonance (1D NMR), and two-dimensional nuclear magnetic resonance (2D NMR).