2,3,7, 8,12,13-Hexakis[2-(2-methoxyethoxy)ethoxy]-tricycloquinazoline: a discogen which allows enhanced levels of n-doping

A synthesis has been developed for 2,3,7,8, 12,13-hexakis[2-( 2-methoxyetho xy) ethoxy]-tricycloquinazoline ( TCQ6EO2M) in which the ethylenoxy side ch ains are introduced before elaboration of the heterocylic core. This discog en gives a hexagonal columnar phase (Col(h)) between 77 and 233 degreesC. n -Doping using potassium metal is facilitated firstly by the electron poor/p i -defficient nature of the core and secondly by the polyethylenoxy side ch ains which complex the potassium K+ counter-ions. The conductivity of the C ol(h) phase of TCQ6EO2M doped with 10 mol% potassium (sigma (parallel to) = 1.1 x 10(-3) S m(-1)) is substantially higher than that previously reporte d for 2,3,7,8, 12,13-hexa(hexylthio) tricycloquinazoline doped with 6 mol% potassium (sigma (parallel to) = 2.9 x 10(-5) S m(-1)). Photoconductivity s tudies of TCQ6EO2M using a time of flight sample configuration show transie nt photocurrents for both holes and electrons. From these an upper limit on the mobility for the electrons is estimated as similar to 10(-4) cm(2) V-1 s(-1) at 150 degreesC which is of the same magnitude as that for hole mobi lities in other columnar discotic liquid crystals.