Different molecular conformation and packing determining mechanochromism and room-temperature phosphorescence

• Published in: Science China materials Vol. 64; no. 11; pp. 2813 - 2823
• Main Authors: Li, Shuhui, Xie, Yujun, Li, Aisen, Li, Xiaoning, Che, Weilong, Wang, Jinfeng, Shi, Heping, Li, Zhen
• Format: Journal Article
• Language: English
• Published: Beijing Science China Press 01.11.2021; Springer Nature B.V
• Subjects: Aggregates; Carbazoles; Chemistry and Materials Science; Chemistry/Food Science; Crystal structure; Crystals; Materials Science; Molecular conformation; Optical properties; Phosphorescence; Planar structures; Red shift; Room temperature; Single crystals; X ray powder diffraction; molecular packing; conformation; mechanochromism; room temperature phosphorescence
• ISSN: 2095-8226; 2199-4501
• DOI: 10.1007/s40843-021-1658-9

The phenomenon that different molecular packing modes in aggregates result in different optical properties has attracted intense attention, since it can provide useful information to establish the relationship between the micro- and macro-world. In this paper, DBTDO-DMAC was designed with 9,10-dihydro-9,9-dimethylacridine (DMAC) as electron donor. DBTDO-DPA and DBTDO-Cz were designed for comparison, which adopted diphenylamine (DPA) with twisted structure and carbazole (Cz) with planar structure as donors, respectively. As expected, two polymorphs (Crystal G and Crystal Y) of DBTDO-DMAC were obtained and exhibited distinct properties. Crystal G originating from planar conformation exhibited mechanochromism (MC) phenomenon and the emission color changed from green to yellow with a redshift of 35 nm after grinding. Nevertheless, Crystal Y with folded conformation displayed obvious room-temperature phosphorescence (RTP) with yellow afterglow. Careful single crystal analyses, powder X-ray diffraction and theoretical calculation reveal that the different emissive behaviors are highly related to the molecular conformation and packing modes. The successful adjustment of molecular conformation provides some guidance in the design of other MC and/or RTP luminogens, broadens the molecule family with the tunable molecular conformation and opens up a new avenue for exploring possible adjustment of molecular packing in aggregates.