Alkyl Chain Length‐ and Polymorph‐Dependent Photomechanochromic Fluorescence of Anthracene Photodimerization in Molecular Crystals: Role of the Lattice Stiffness
Cheng‐Zong Kuo, Li‐Yun Hsu, Yushan Chen, Kenta Goto, Subhendu Maity, Yi‐Hung Liu, Shie‐Ming Peng, Kien Voon Kong, Teruo Shinmyozu, Jye‐Shane Yang
Abstract
Anthracene-pentiptycene hybrid systems 1-Cn, where n refers to the number of carbon atoms in the linear alkyl chain, crystallize in three different polymorphs, denoted Y (yellow), G (green), and B (blue) forms in terms of the fluorescence color. While all Y-form crystals show the same yellow-to-blue fluorescence color response to the photomechanical stress generated by the anthracene [4+4] photodimerization reaction, the four G forms exhibit distinct photomechanofluorochromism (PMFC): from green to blue for G-1-C4, to orange for G-1-C7, to red for G-1-C8, and to red then blue for G-1-C9, and the B forms show no photochromic activity. The intriguing RGB three-color PMFC and abnormal topochemical reactivity of G-1-C9 are attributed to inherent softness of the crystal lattice.