20200-59-3Relevant academic research and scientific papers
Comparative Evaluation of Substituent Effect on the Photochromic Properties of Spiropyrans and Spirooxazines
Balmond, Edward I.,Tautges, Brandon K.,Faulkner, Andrea L.,Or, Victor W.,Hodur, Blanka M.,Shaw, Jared T.,Louie, Angelique Y.
, p. 8744 - 8758 (2016/10/14)
Spiropyrans and spirooxazines represent an important class of photochromic compounds with a wide variety of applications. In order to effectively utilize and design these photoswitches it is desirable to understand how the substituents affect photochromic properties, and how the different structural motifs compare under identical conditions. In this work a small library of photoswitches was synthesized in order to comparatively evaluate the effect of substituent modifications and structure on photochromism. The library was designed to modify positions that were believed to have the greatest effect on C-O bond lability and therefore the photochromic properties. Herein we report a comparative analysis of the UV and visible light responses of 30 spiropyrans, spiroindolinonaphthopyrans, and spirooxazines. The influence of gadolinium(III) binding was also investigated on the library of compounds to determine its effect on photoswitching. Both assays demonstrated different trends in substituent and structural requirements for optimal photochromism.
Photochromism of spirobenzopyranindolines and spironaphthopyranindolines
Chibisov,Goerner
, p. 424 - 431 (2007/10/03)
The photocolouration of five spiro[2H-1-benzopyran-2,2′-indoline] compounds (1-5) and two spironaphthopyranindolines (6, 7) to give the ring-opened merocyanine(s) and the subsequent thermal relaxation back to the closed form was studied. A trans-merocyanine but no cis-photoisomer were detected for 1-7 using λexc = 308 nm and a singlet pathway accounts for photocolouration. In contrast to nitrospiropyrans the yield of colouration of spiropyrans is essentially independent of solvent polarity. The relaxation times at 25°C range from 0.01 s for 6 in methylcyclohexane to 17 s for 5 in ethanol, which is due to differences in both activation energies (65-80 kJ mol-1) and the pre-exponential factor (1012-1014 s-1). The photomerocyanine yield is substantially increased upon naphthalene- or acetone-sensitized excitation, where otherwise the same spectral changes, relaxation time and activation parameters were found. Upon excitation of the trans-merocyanine (λexc = 530 nm), a cis-merocyanine with lifetime in the sub ms range could be detected at lower temperatures. Deactivation of the excited trans-merocyanine occurs mainly in the excited singlet state. For 4 and 5, due to an internal heavy-atom effect of bromine substituents, and for 1, a triplet state as a precursor of the cis- and trans-merocyanines could be observed. The effects of structure and medium properties on the photoprocesses are described and the mechanisms of photochromism and thermal decolouration are discussed.
