Toward new materials for organic electroluminescent devices: synthesis, structures, and properties of a series of 2,5-diaryl-3,4-diphenylsiloles

A series of 2,5-diaryl-3,4-diphenylsiloles, with various mono-substituted phenyl groups, extended pi-conjugated groups, and heteroaryl groups as aryl groups at the 2,5-positions, has been prepared by a one-pot synthesis from bis(phenylethynyl)silanes based on the intramolecular reductive cyclization followed by the palladium-catalyzed cross-coupling with aryl halides. Crystal structures and chemical reactivities toward the alkaline desilylation reactions have been studied on the 2,5-bis(p-mono-substituted phenyl)silole derivatives to elucidate the effects of the p-substituents. The UV-visible absorption and fluorescence spectra, and cyclic voltammetry of the 2,5-diarylsiloles have been systematically evaluated. Their photophysical properties as well as their electronic structures significantly depend on the nature of the 2,5-aryl groups.