Effects of peripheral ring fluorination on the photophysical properties of hexaarylbenzenes

Unsymmetrical and C3-Symmetrical Partially Fluorinated Hexaarylbenzenes: Effect of Terminal Alkoxy Chain Length on Photophysical and Thermophysical Behavior

“…Unsymmetrical partially fluorinated HABs 1a-f and symmetrical analogs 2a-f were synthesized using cobalt-catalyzed [2 + 2 + 2] cyclotrimerization of donor-π-acceptor-type fluorinated tolanes 3a-f, according to the reaction sequence shown in Scheme 1 [12]. Although the synthetic procedures and compound characterization data for 1a and 2a with a methoxy substituent on the electron-rich aromatic ring have been reported previously [12], the synthetic methods and characterization data for 1b-f and 2b-f are described below. The 1 H, 13 C, and 19 F-NMR spectra of 1b-f and 2b-f are demonstrated in Figures S2-S30, and their spectra proved that the compounds were of sufficient purity to enable evaluation of their photophysical behavior.…”

“…Methoxy-substituted partially fluorinated HABs 1a and 2a, previously reported, showed only a phase transition from a crystalline (Cr) to an isotropic (Iso) phase, with T m values of approximately 271 and 313 • C, respectively [12]. T m is defined here as the temperature at which a Cr phase transitions to another.…”

“…Our group recently synthesized and evaluated photophysical behavior for three each of unsymmetrical 1,2,4-substituted HABs and C 3 -symmetrical 1,3,5-substituted HABs [12]. The first is HAB molecules that do not have any fluorine atoms on the lateral sides of the peripheral aromatic rings (Figure 1a); the second is a partially fluorinated HAB molecule in which fluorine atoms are introduced only on the lateral sides of the aromatic rings with a CF 3 terminal group among the peripheral aromatic rings (Figure 1b); and the third is polyfluorinated HAB molecules in which the lateral sides of the peripheral aromatic rings are perfluorinated (Figure 1c).…”

“…The photophysical property evaluation of the above three unsymmetrical and C3-symmetrical HABs revealed that partially fluorinated HABs exhibited distinct photophysical properties, such as different photoluminescence (PL) wavelengths due to differences in molecular symmetry and higher fluorescence quantum yields (ΦPL) when compared to less-fluorinated and polyfluorinated analogs. Research concept and chemical structures of (a-c) various hexaarylbenzenes reported in our previous studies [12] and (d) partially fluorinated hexaarylbenzenes, e.g., 1b-f and 2b-f, with a various length of alkoxy chain used in this study.…”

“…The flexible chains introduced at the end of the peripheral ring of HAB have a significant effect on the molecular aggregated structures, contributing to dramatic alterations in solid-state luminescence properties and the emergence of liquid-crystalline states [13,14], in which luminescent liquid crystals with both properties are well recognized as one of the promising functional materials [15]. As part of our research project on partially fluorinated HAB-based fluorescent molecules, we synthesized unsymmetrical partially Research concept and chemical structures of (a-c) various hexaarylbenzenes reported in our previous studies [12] and (d) partially fluorinated hexaarylbenzenes, e.g., 1b-f and 2b-f, with a various length of alkoxy chain used in this study.…”