Self-assembling behavior of binary mixture of hexa-peri-hexabenzocoronene derivatives with different molecular symmetry

The self-assembly and mesophase behavior of a series of mixtures of hexa-peri-hexabenzocoronene (HBC) derivatives carrying alkyl chains of different lengths at different positions and thus of different molecular symmetry (C₁- and D_3h-symmetry) were examined by powder X-ray diffractometry, UV–vis spectrometry, photoluminescence, polarizing optical microscopy, and differential scanning calorimetry. Significant reduction of isotropic phase transition temperature/clearing temperature was observed compare to single component symmetric analogues. The chain length modulates the mesophase behavior existed in the mixture. In particular, with long dodecyl groups, the mixture exhibited excimer/exciplex formation as well as aggregation induced emission phenomena in the non-polar solvent of hexane. Formation dynamics of intermolecular excimer/exciplex was studied by nuclear magnetic resonance and UV–vis spectroscopic method.