Three truxene derivatives functionalized with alkyl chains, either attached directly or distanced by linking phenyl or ethynyl groups, self-assemble in solution and induce the gelation of different solvents in spite of not being endowed with groups able to establish strong directional interactions. A (1)H NMR study points to face-to-face alternating π-stacked motifs at the origin of nucleation. Solvents play an important role in modulating the aggregation of these derivatives giving rise to fibrous or spherical superstructures. Analysis of the influence of different solvents on the morphology of the aggregates provides a better understanding of the various stages of the hierarchical self-assembly. The way in which alkyl chains are attached to the central core also strongly affects the self-assembling properties and gelation ability of this series. Phenyl spacers present the highest association constants in solution and give rise to gelation in a broader range of solvents. This behavior has been rationalized by means of (1)H NMR spectroscopy, X-ray powder diffraction, SEM, and photophysical measurements. Interestingly, it was found that these compounds in the gel state exhibit unusual emission properties most likely arising from the formation of excimers, which evidences that π-π interactions also occur in the excited state.
Keywords: gelators; liquid crystals; nanostructures; pi interactions; self-assembly.
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