New photochromic indoline spiropyrans containing cationic substituent in the 2H-chromene moiety

New indoline spiropyrans containing conjugated cationic fragments and bulky substituents in the 2H-chromene moiety were synthesized by a simple one-pot method. The structures of the obtained compounds were confirmed by H-1 and C-13 NMR (including 2D methods) and IR spectroscopy, as well as by element analysis and HRMS. Molecular structure of 1,3,3-trimethy1-6'-formy1-8'-benzyl-spiro[indoline2,2'-2H-chromene] was refined by single crystal X-ray. A comparative analysis of the spectral and photochromic properties of salt spiropyrans and similar structures without a cationic fragment was carried out. It was found that the introduction of the cationic substituent at the 6'-position of the 2-H-chromene moiety leads to a significant increase in the photoinduced isomer's lifetime. (C) 2018 Elsevier B.V. All rights reserved.