Halogen-bonded Liquid Crystals - Halogen Bonding: Fundamentals and Applications - page 160

Halogen-bonded Liquid Crystals

Duncan W. Bruce
Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
[e-mail]

1 rea le ..................................... 161

2 An Introduction to Thermotropic Liquid Crystals .............. 162

2.1 LowMolarMassLiquidCrystals........................ 162

2.2 HighMolarMassLiquidCrystals ....................... 165

3 Characterisation of Liquid Crystal Mesophases ............... 166

4 Liquid Crystals Formed Through Non-covalent Interactions ........ 167

4.1 QuadrupolarInteractions............................ 167

4.2 Charge-transferInteractions .......................... 168

5 y r gen i g ............................... 169

6 Halogen-bondedLiquidCrystals ........................ 174

7 Future Prospects ................................ 179

References ....................................... 179

Abstract This chapter discusses the relatively new discovery of liquid crystallinity in-
duced by halogen bonding. Liquid crystals are first introduced and then, to give the
work some context, background information is given concerning liquid crystal phases in-
duced by other, non-covalent interactions. In particular, hydrogen bonding is examined,
as the two interactions are rather similar as are the molecular components that might be
used as the acceptor. Low molar mass and polymeric halogen-bonded mesogens are then
described and future prospects are evaluated.

1
Preamble

As described most elegantly elsewhere in this volume, the halogen bond is
an intermolecular, charge-transfer interaction between a Lewis base and an
electron-deficient halogen. Other chapters that accompany this chart its use
in, for example, supramolecular chemistry, molecular conductors and coordi-
nation chemistry. In this chapter, a much more recent application of halogen
bonding is described, namely in the realisation of liquid-crystalline materials.
The literature amounts to few published papers to date, but nonetheless
the potential is significant and there is a good deal of work from the author's
laboratory that will find its way to publication in the coming period.