Heteroaggregation between isomeric amido-ethynyl-amidohelicene tridomain oligomers.

Three isomers, i.e., P4M5P4-1, M4P5M4-1, and M4M5M4-1, of amido-ethynyl-amidohelicene tridomain oligomers were synthesized. P4M5P4-1 formed four homoaggregate states, i.e., all-dimer, amido-dimer, ethynyl-dimer, and random-coil states, by independent aggregation and disaggregation at the ethynyl and amido domains. Then, possible combinations of heteroaggregation were examined between the isomeric tridomain oligomers P4P5P4-1, P4M5P4-1, M4P5M4-1, and M4M5M4-1. When P4P5P4-1 and P4M5P4-1 were mixed in THF, to which trifluoromethylbenzene was added, heteroaggregates with an all-dimer structure were formed without forming homoaggregates. The heteroaggregation initially occurred at the central ethynyl domain, which was followed by the aggregation at the amido domains. Heteroaggregates were also formed using the combinations P4P5P4-1/M4M5M4-1 and P4M5P4-1/M4P5M4-1, and the results indicated an important role for the central ethynyl domain for heteroaggregation.