Complementary polytopic interactions (CPI) as revealed by molecular modelling using the XED force field

To explain 1 : 1 compound formation between HAT (2,3,6,7,10,11-hexaalkoxytr iphenylene) discogens and PTP (2,3,6,7,10,11-hexakis(4-alkylphenyl)tripheny lene or PDQ (2,3,6,7,10,11-hexakis(4-alkylphenyl)dipyrazino[2,3, f 2',3'-h] quinoxaline) derivatives we have exploited the XED (extended electron distr ibution) force field method. This is the only method that we have found whi ch is able to explain why compound formation occurs in some cases but not i n others. Not only is the force field successful in the case of these disco gens and in a number of systems investigated by Hunter and Rebek, but we al so show that it can explain the observed stability of other pi -stacked sys tems including HAT-TNF (trinitrofluorenone), benzene-hexafluorobenzene, tri phenylene-perfluorotriphenylene, benzene multiyne-TNF systems and complemen tary mixtures of selectively fluorinated 1,4-bis(phenylethynyl) benzene der ivatives. In each case the interaction is expressed as a sum of atom-based van der Waals and multipole interactions: a complementary polytopic interac tion.