Effects of substitution position on crystal packing, polymorphism and crystallization-induced emission of (9-anthryl)vinylstyrylbenzene isomers†
Three (9-anthryl)vinylstyrylbenzene (ASB) position isomers were synthesized and compared. Substitution position affects temperature-induced polymorphism, crystal packing and crystallization-induced emission (CIE) properties. Different from 1,2-ASB and 1,4-ASB, 1,3-ASB undergoes a crystal-to-crystal phase transition upon heating. The crystal structure of a new phase (1,3-ASB-β) was successfully solved. Thus, the solid emission of 1,3-ASB could be tuned by polymorphism. In contrast, the solid emission of 1,4-ASB is controlled by its crystallinity. In the crystal structures of 1,2-ASB and 1,3-ASB-β, the adjacent interacting anthryls are inclined to adopt an edge-to-face configuration with C–H⋯π interactions. In contrast, the adjacent anthracene rings in the 1,4-ASB crystals are parallel to each other with π⋯π interactions. Furthermore, multiple intermolecular interaction modes such as C–H⋯π and H⋯H interactions coexist in the crystal structure of 1,4-ASB, which collectively results in a closer packing. Interestingly, 1,4-ASB displays CIE behaviour. In contrast, the emission of the other two isomers is quenched in the solid state. The effect of substitution position on the photophysical properties is systematically studied.