A Comparison of CPI and Charge-transfer Two-component Columnar Phases

The phase diagram for the binary mixture of 2,3,6,7,10,11-hexakis (4'-nonylphenyl) triphanylene and 2,3,6,7,10,11-hexakis(hexyloxytriphenylene) shows formation of a 1:1 compound with a higher clearing temperature and a greater mesophase range than either of the individual components. This and related CPI (Complementary Polytopic Interaction) compounds are compared to 'charge transfer compounds' formed on adding 2,4,7-trinitrofluoen-9-one (or one of its derivatives) to a 2,3,6,7,10,11-hexaalkyloxytriphenylene (or other discogen). There are significant differences between the actual phases formed but in terms of the local molecular packing and in terms of the stabilising interactions involved they are essentially the same. Both can be rationalised using the XED (extended electron distribution) model. In this it is assumed that dispersed coulombic and van der Waals interactions dominate and that other contributions are small.