A liquid-crystalline perylene tetracarboxylic bisimide derivative bearing trisiloxan-2-yl moieties: influence on mesomorphic properties and electron transport

Mesomorphic and electron transport properties are compared for liquid-crystalline (LC) perylene tetracarboxylic bisimide (PTCBI) derivatives bearing linear disiloxane and trisiloxane chains, as well as bis(trimethylsiloxanyl) methylsilyl(trisiloxan-2-yl) groups. In contrast to alkyl-substituted analogues, the PTCBI derivative bearing bulky trisiloxan-2-yl moieties exhibits a more ordered columnar phase and higher electron mobility compared to that bearing linear trisiloxane chains. In spite of the bulkiness, the trisiloxan-2-yl moieties do not inhibit closed pi-pi stacking within the columnar aggregates. Therefore the electron mobility in the ordered columnar phase of the compound bearing the branched trisiloxan2- yl moieties was 0.05 cm(2) V-1 s(-1) at room temperature and it exceeded 0.1 cm(2) V-1 s(-1) at 120 degrees C.