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

• Published in: Liquid crystals Vol. 28; no. 12; pp. 1739 - 1748
• Main Authors: Boden, Neville, Bushby, Richard J., Donovan, Kevin, Liu, Quanying, Lu, Zhibao, Kreouzis, Theo, Wood, Andrew
• Format: Journal Article
• Language: English
• Published: Taylor & Francis Group 01.12.2001
• ISSN: 0267-8292; 1366-5855
• DOI: 10.1080/02678290110082383

A synthesis has been developed for 2,3,7,8,12,13-hexakis[2-(2-methoxyethoxy)ethoxy]-tricycloquinazoline (TCQ6EO2M) in which the ethylenoxy side chains are introduced before elaboration of the heterocylic core. This discogen gives a hexagonal columnar phase (Col h ) between 77 and 233°C. n-Doping using potassium metal is facilitated firstly by the electron poor/π-deficient nature of the core and secondly by the polyethylenoxy side chains which complex the potassium K + counter-ions. The conductivity of the Col h phase of TCQ6EO2M doped with 10 mol % potassium (σ ∥ = 1.1 x 10 -3 S m -1 ) is substantially higher than that previously reported for 2,3,7,8,12,13-hexa(hexylthio)tricycloquinazoline doped with 6 mol % potassium (σ ∥ = 2.9 x 10 -5 S m -1 ). Photoconductivity studies of TCQ6EO2M using a time of flight sample configuration show transient photocurrents for both holes and electrons. From these an upper limit on the mobility for the electrons is estimated as ~10 -4 cm 2 V -1 s -1 at 150°C which is of the same magnitude as that for hole mobilities in other columnar discotic liquid crystals.