Ueki, Masanori, Kimura, Yusuke, Yamamoto, Yuma, Nishida, Jun-ich, Kitamura, Chitoshi, Tanaka, Mirai, Ikeda, Hiroshi, and Kawase, Takeshi
The substituent effect on optical properties of 3,14-diphenyl-17,17-di( n -pentyl)tetrabenzofluorene derivatives bearing electron-withdrawing groups (NC, CH 3 OCO, CH 3 SO 2 , and OHC) at 4-position of the phenyl groups were investigated. These compounds were readily prepared by using Suzuki–Miyaura cross-coupling as a key step. The 4-cyano, 4-methoxycarbonyl, and 4-methylsulfonyl derivatives display intense blue to blue-green fluorescence in CH 2 Cl 2 and in the solid states. On the other hand, the title compound forms two polymorphs, and thus, exhibit crystallochromism in fluorescence; the prismatic crystal emits intense yellow fluorescence, and the other crystal form does blue-green fluorescence. Moreover, the compound shows large solvatofluorochromism (Δ λ EM = 67 nm). The crystallographic analysis of the prismatic crystal reveals that the tetrabenzofluorene moiety of the compound possesses a helical structure with a C 2 symmetry and the molecules form a herringbone-like structure. The density function theory calculations predict the remarkable intramolecular charge-transfer character of the compound. The prediction is in good agreement with the observed fluorescence properties. [ABSTRACT FROM AUTHOR]