Synthesis and luminescence properties of four-armed conjugated structures containing 1,3,4-oxadiazole moieties

New 9,10-bis(phenylethynyl)anthracene cored, four-armed conjugated structures in which the 1,3,4-oxadiazole ring is utilized to link the surface alkyl tail groups, were synthesized and the luminescence properties of thin films prepared therefrom were studied. It was found that the four-armed compound (ANTH-OXA6t-OC₁₂) with the dodecyloxy surface group is a high glass transition temperature (T_g: 211°C) material and exhibits good solubility in common organic solvents and, surprisingly, results in good quality thin films by spin-coating from solutions. In contrast, the compound with tert-butyl surface groups shows poor solubility and gives films of inferior quality. When the films were exposed to UV light of 335 nm, they emitted mainly strong red light (500-750 nm) with much weaker emission at 375-450 nm. The (phenylethynyl)anthracene core is the only red light emitting chromophore in the structure, and the diphenyl oxadiazole moieties are the shorter wavelength light emitters. In contrast, an electroluminescence (EL) device having the configuration of ITO/PEDOT-PSS/ANTH-OXA6t-OC₁₂/Li: Al emits only red light with an external quantum efficiency of 0.02% indicating that the outer diphenyl oxadiazole moieties act only as electron transporters.