Alkyl Chain Length‐ and Polymorph‐Dependent Photomechanochromic Fluorescence of Anthracene Photodimerization in Molecular Crystals: Role of the Lattice Stiffness

• Published in: Chemistry : a European journal Vol. 26; no. 50; pp. 11511 - 11521
• Main Authors: Kuo, Cheng‐Zong, Hsu, Li‐Yun, Chen, Yu‐Shan, Goto, Kenta, Maity, Subhendu, Liu, Yi‐Hung, Peng, Shie‐Ming, Kong, Kien Voon, Shinmyozu, Teruo, Yang, Jye‐Shane
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 04.09.2020; Wiley Subscription Services, Inc
• Subjects: Anthracene; Atomic properties; Chains; Chemistry; Chemistry, Multidisciplinary; Color; crystal engineering; Crystal lattices; Crystals; Fluorescence; Hybrid systems; photochemistry; Physical Sciences; pi interactions; polymorphism; Science & Technology; Softness; Stiffness; fluorescence; photochemistry; DIMER; BEHAVIOR; polymorphism; STRESS; crystal engineering; pi interactions; SOLID-STATE
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202000353

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. Glowing colors: The alkyl chain length in anthracene–pentiptycene hybrid π systems affects the crystal polymorphism and lattice stiffness and in turn the topochemical reactivity, and this results in various types of fluorescence color responses triggered by photomechanical stress, including unprecedented red–green–blue (RGB) three‐color photomechanofluorochromism (PMFC).