Novel Photochromic 2H-Chromenes with π-Donor Substituents in the 2H-Pyran Ring

• Published in: Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals Molecular crystals and liquid crystals, 1997-05, Vol.297 (1), p.213-218
• Main Authors: Metelitsa, A. V., Knyazhansky, M. I., Koblik, A. V., Muradyan, L. A., Lukyanov, S. M., Minkin, V. I.
• Format: Article
• Language: English
• ISSN: 1058-725X
• DOI: 10.1080/10587259708036124

A series of novel photochromic 2H-chromenes containing the ethynyl or ethoxy groups in position 4 (I, II) and an annelated pyrrole ring (III, IV) have been synthesized and their spectral and photochromic properties studied. The chromenes I - IV are characterized by high rates of thermal bleaching reaction in liquid solutions at room temperature. Longwave absorption bands of the chromenes I have their maxima at 295-308 nm, whereas their photoisomers absorb at λ max = 437 nm (glassy isopentane-isopropanol, 4:1 solvent, T< 200 K). For the type chromenes III, IV the longwave absorption bands are found in the regions of λ max = 323-325 nm (ring-closed form A) and λ max = = 675-678 nm (ring-opened form B).