Synthesis and properties of organosilicon polymers containing 9,10-diethynylanthracene units with highly hole-transporting properties

Coupling reactions of 9,10-di(lithioethynyl)anthracene with dichloromono-, di-, and trisilanes, Cl(SiR2)mCl (m=1–3) gave polymers composed of alternating 9,10-diethynylanthracene and organosilicon units. With dichlorotetraorganodisilanes, the corresponding dianthracenophanes composed of two 9,10-diethynylanthracene units linked by tetraorganodisilanylene bridges were also obtained, together with the polymers. The emission spectra of the polymers with di- and trisilanylene units suggest that intrachain aggregation takes place in solution, although it is not obvious for the silanylene polymer. Cyclic voltammetric (CV) analysis of the polymers shows the evident dependence of the CV profiles on the lengths of the silicon chain between the diethynylanthracene units. When the polymer films were treated with FeCl3 vapor, the films became conducting with the maximum conductivities in the order of 10−5 S cm−1. The double-layer-type electroluminescent (EL) devices were fabricated using these polymers as a hole-transporting layer and tris(8-quinolinolato)aluminum (III) complex (Alq) as an electron-transporting-emitter layer. The turn-on voltage of the devices became higher and the maximum current density smaller, as increasing the number of silicon atoms in a polymer unit from m=1 to 3. The highest luminance of 1300 cd m−2 was obtained from the device based on the silanylene-diethynylanthracene polymer.