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Pure Appl. Chem., 2010, Vol. 82, No. 11, pp. 1993-2003

Published online 2010-08-27

Homeotropic alignment through charge-transfer-induced columnar mesophase formation in an unsymmetrically substituted triphenylene derivative

Juanjuan Li1, Zhiqun He1*, Huan Zhao1, Hemant Gopee2, Xiangfei Kong1, Min Xu1, Xinxin An3, Xiping Jing3 and Andrew N. Cammidge2*

1 Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044, China
2 School of Chemistry, University of East Anglia, Norwich NR4 7TJ, UK
3 College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China

Abstract: An unsymmetrically substituted triphenylene, with two adjacent chloroethoxyethyl lateral flexible chains, was synthesized and characterized. Although this compound showed no mesomorphic behavior, it formed a donor–acceptor charge-transfer complex with 2,4,7‑trinitrofluorenone (TNF). The resulting 1:1 complex has been investigated using UV–vis and IR spectroscopy, optical microscopy, thermal analysis, and X-ray diffraction. A columnar mesophase with hexagonal symmetry was found. More interestingly, this charge-transfer complex can be easily aligned on a glass surface in a homeotropic orientation, which is stable at room temperature (RT) and over a wide temperature range.