Structure and Properties of 1,3,3-Trimethyl-6′-chlorospiro[indoline-2,2′-2H-chromene]

Indoline spiropyran containing an σ-acceptor chlorine atom in 6′ position of the 2H-chromene part of the molecule was synthesized and studied. The use of 1,2,3,3-tetramethyl-3H-indolium perchlorate as a starting compound made it possible to achieve higher product yields as compared to previous studies. The molecular structure of the compound was established by single crystal X-ray diffraction analysis. The features of the crystal structure and intermolecular interactions were investigated using CrystalExplorer17 software package. The photochromic behavior in acetonitrile solution was studied for the first time. It was found that the merocyanine form of spiropyran is characterized by an absorption maximum at 592 nm, which is 37 nm closer to the range of the “biological window” in comparison with the nitro-substituted analog.