Synthesis and properties of liquid pyrazine dyes

Six 2,5-diamino-3,6-dicyanopyrazine dyes with medium to long length alkyl chains on their amino groups were newly synthesised and their fundamental properties investigated, including their derivatives, focusing on liquefaction at room temperature. The butyl, pentyl, hexyl, heptyl, octyl, and dodecyl substitutions realised liquefaction of the dye chromophore. These liquid dyes exhibited relatively good fluorescent properties in the liquid state. The dodecyl derivative showed the largest fluorescence efficiency of 0.59 in the liquid state among the derivatives and was used in an organic light-emitting device. The efficient yellow EL emission peaked at 593 nm with a 10 V turn-on voltage of the device and a maximum brightness of 336 cd/m(2) at 14 V.