A photochromic naphthopyran dye activated by the intramolecular hydrogen bond and its photodynamics in the ormosil matrix coating

Naphthopyran dyes are one important family of photochromic compounds, and the understanding of the effects of internal and external factors on their functions is crucial to their development. In this study, the intramolecular hydrogen bond and host materials have been demonstrated to be essential to their applications. A novel N-(4-chlorophenyl)-3,3-diphenyl-3H-benzo[f]chromene-5-carboxamide (NPase) dye is designed and synthesized based on the condensation reaction of 1,1-diphenylprop-2-yn-1-ol and N-(4-chlorophenyl)-3-hydroxynaphthalene-2-carboxamide in an acidic solution. Both the X-ray analysis of the NPase single crystal and theoretical calculation are used to investigate the molecular configuration and optical property. After the introduction of an intramolecular hydrogen bond by the substitute in the dye, an unusual coplanar structure is theoretically proposed and experimentally confirmed, which affects the tautomerization energy and bathochromic-shift in absorption characteristics greatly. Our results also confirm that the flexible segment of polymethylsiloxane (PDMS) in the host hybrid coating (PMS–PDMS) materials can accelerate the spectrokinetics of NPase which indicates a faster conversion process.