Synthesis of π-conjugated oligomers containing dithienosilole units

pi-Conjugated oligomers having a dithienosilole unit(s) in the backbone were prepared, and their optical properties were examined. Their UV-vis absorption spectra and the emission spectra display maxima at 395-498 nm and at 498-576 nm, respectively, which are at longer wavelength than the oligomers that do not contain silole units with the same pi-conjugated chain length. This clearly demonstrates the influence of silole segments in enhancing the conjugation in the oligomer backbone. The crystal structure of a bi(dithienosilole) derivative was determined by X-ray crystallographic analysis, showing high coplanarity of the two dithienosilole rings. One of the present dithienosilole-containing oligomers was found to be FET active in its vapor-deposited film as well as spin-coated film with a hole mobility of mu = 2.6 x 10(-5) cm(2)/V s and mu = 1.2 x 10(-7) cm(2)/V s, respectively.