209051-94-5Relevant articles and documents
Ultrafast Dynamics of the Transoid-cis Isomer Formed in Photochromic Reaction from 3H-Naphthopyran
Brazevic, Sabina,Baranowski, Miko?aj,Sikorski, Marek,Rode, Micha? F.,Burdziński, Gotard
, p. 1402 - 1407 (2020/06/17)
Recent efforts in designing new 3H-naphthopyran derivatives have been focused on efficient coloration process with a short fading time of the colored transoid-cis TC isomer. It is desirable to avoid photoisomerization of TC leading to transoid-trans TT isomers in the photoreaction. Long lifetime of TT can hamper fast applications such as dynamic holographic materials and molecular actuators, the residual color is one of the serious issues for photochromic lenses. Herein we characterize the photophysical and photochemical channels of TC excited state deactivation competing with the unwanted TC→TT isomerization process. Transient absorption spectroscopy reveals a very short lifetime of the singlet excited TC (≈0.8 ps) and its deactivation channels as S1→S0 internal conversion (major), intersystem crossing S1→T1, pyran ring formation, photoenolization and TC→TT isomerization. Computations support the S1→S0 and T1→S0 channels as responsible for photostabilization of the TC form.
Solid-state photochromism of chromenes: Enhanced photocoloration and observation of unstable colored species at low temperatures
Harada, Jun,Ueki, Keigo,Anada, Masahide,Kawazoe, Yuta,Ogawa, Keiichiro
body text, p. 14111 - 14119 (2012/01/19)
Solid-state photochromism of benzopyrans and naphthopyrans (chromenes) was investigated in the temperature range between 300 and 80 K. Variable-temperature diffuse reflectance spectroscopy of microcrystalline powders showed that the extent of photocoloration was greatly enhanced at low temperatures. All the chromenes examined exhibited solid-state photochromism at low temperatures, even when they showed little or no photocoloration at room temperature. The solid-state photochromic properties of the chromenes were quite similar to those reported for analogous photochromic compounds of spiropyrans and spirooxazines, which indicates that these classes of compounds are generally photochromic even in the solid state. Photobleaching reactions of the colored merocyanine forms proceeded at low temperatures through the formation of a colorless intermediate, instead of directly resuming the original closed form. In addition to two stable planar merocyanine forms, which are usually observed in the photochromic reactions in solution, photoreactions at low temperatures allowed us to observe unstable colored species, which were tentatively assigned as nonplanar cisoid forms, and were stabilized in the solid state at low temperatures.
Photophysics and kinetics of naphthopyran derivatives, part 3: A general procedure to uniquely identify the kinetic and spectroscopic parameters of ABC(2k,2φ) systems and application to naphthopyran reactions
Maafi,Brown
, p. 421 - 430 (2008/02/09)
A new procedure has been developed with the aim of determining the kinetic and spectroscopic parameters of any photochemical systems of the generic ABC(2k,1φ) and ABC(2k,2φ) types. General expressions of the colorability and the equilibrium concentration ratio of two (of the three involved) species at a photostationary state or a state of thermal equilibrium have been derived. The procedure has been successfully applied to achieve unique identifiability for the seven sequences of the ABC(2k,1φ and 2φ) type that may represent naphthopyran dynamics. It is demonstrated that the reactivity of this particular compound is certainly described by a higher kinetic level than those (three or four reaction steps) considered in the present study.
