Development of Donor‐π‐Acceptor‐Type Fluorinated Tolanes as Compact Condensed Phase Luminophores and Applications in Photoluminescent Liquid‐Crystalline Molecules

Abstract

Fluorinated tolanes, produced by introducing fluorine atoms into one of the aromatic rings of tolane, emitted almost no fluorescence in a solution state, but the fluorescence intensity increased dramatically in the crystalline state because of intermolecular H⋅⋅⋅F hydrogen bonds. The photoluminescent (PL) colors depend on the molecular orbitals, dipole moments, and molecular aggregated structures can be varied by controlling terminal substituents along the major molecular axis. The introduction of a long alkoxy or semifluoroalkoxy unit as a flexible chain into the terminal positions along the major molecular axis induced the formation of a liquid‐crystalline (LC) phase; fluorinated tolanes act both as luminophores and as mesogens, leading to the molecular design of new photoluminescent LC molecules (PLLCs). The results also indicated that a fluorinated tolane dimer, which consists of two fluorinated tolanes linked by a flexible alkylene spacer, also becomes a novel PLLC.

(1E)-1,2-Diaryldiazene Derivatives Containing a Donor–π-Acceptor-Type Tolane Skeleton as Smectic Liquid–Crystalline Dyes

“…Recently, our group explored molecules that have both LC and photoluminescence properties and successfully developed donor-π-acceptor (D-π-A)-type tolane derivatives that have an electron-donating alkoxy group and an electron-withdrawing cyano group at their molecular ends [17][18][19]. Among our achievements, the D-π-A-type tolane bearing a decyloxy (C10H21O) chain formed a nematic (N) LC phase as a mesophase (Figure 1a) [19].…”