Faculty of Physics, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 2, 61-614, Poznan, Poland.
Faculty of Chemistry, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 8, 61-614, Poznan, Poland.
Chemphyschem. 2020 Jul 2;21(13):1402-1407. doi: 10.1002/cphc.202000294. Epub 2020 Jun 8.
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 S →S internal conversion (major), intersystem crossing S →T , pyran ring formation, photoenolization and TC→TT isomerization. Computations support the S →S and T →S channels as responsible for photostabilization of the TC form.
近年来，设计新型 3H-萘并吡喃衍生物的重点一直是具有较短褪色时间的高效着色过程，其中有色反式-顺式 TC 异构体的褪色时间较短。理想情况下，应避免 TC 的光异构化导致光反应中形成反式-反式 TT 异构体。TT 的长寿命会阻碍动态全息材料和分子致动器等快速应用，残余颜色是光致变色镜片的严重问题之一。在此，我们对 TC 激发态失活的光物理和光化学通道进行了表征，这些通道与不需要的 TC→TT 异构化过程竞争。瞬态吸收光谱揭示了 singlet 激发态 TC（≈0.8 ps）及其失活通道的非常短寿命，如 S →S 内转换（主要）、系间窜越 S →T 、吡喃环形成、光烯醇化和 TC→TT 异构化。计算支持 S →S 和 T →S 通道负责 TC 形式的光稳定性。
