Phenanthro[9,10-d]imidazole with thiophene rings toward OLEDs application

A series of phenanthro [9,10-d]imidazole derivatives with thiophene units were synthesized using the Debus-Radziszewski reaction. A study of the optical, electrochemical and thermal properties of the new compounds was conducted. All derivatives were found to be thermally stable, with high melting temperatures (250-267 degrees C) and with the beginning of decomposition starting above 350 degrees C. They underwent the multistage electrochemical reduction. All phenanthro [9,10-d]imidazole derivatives were luminescent in solution and in solid state. In solution they emitted radiation with maximum emission band located at 414-461 nm with photoluminescence quantum yields in the range of 56%-64% in chloroform. As films they emitted blue light with Phi(PL) ranging from 12 to 23%. The possibility of applying one of the synthesized compound in optoelectronics devices was studied as well. The devices showed intense electroluminescence which can be further enhanced by increasing the content of 2-(2,2'-bithiophen-5-yl)-1-phenyl-1H-phenanthro [9,10-d]-imidazole in the active layer.