Tunable molecular packing modes <i>via</i> H- or J-aggregates in the supramolecular helical nanostructures from an achiral <i>C</i><sub>3</sub> symmetric molecule.

Lu, Yi; Shen, Zhaocun; Lian, Changshuo; Wu, Jie; Liu, Minghua; Guo, Zongxia · Soft Matter · 2023

basic_science · Level V

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Abstract

The self-assembly of a <i>C</i><sub>3</sub>-symmetric molecule benzene-1,3,5-tricarboxylate substituted with methyl cinnamate (BTECM) has been investigated by a reprecipitation method in H<sub>2</sub>O and cetyltrimethylammonium bromide (CTAB) aqueous solution, respectively. The nanostructures and characteristics of the assemblies were monitored by UV-Vis spectroscopy, fluorescence (FL) spectroscopy, circular dichroism (CD) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that helical nanostructures were successfully assembled from the achiral <i>C</i><sub>3</sub> molecule BTECM. More importantly, the helices aggregated <i>via</i> different packing modes in H<sub>2</sub>O and CTAB aqueous solution. In H<sub>2</sub>O, the nanostructures underwent a process of particles, fibers and helices <i>via</i> H-type aggregate upon aging. In the case of CTAB aqueous solution (1.2 mM), the helices were translated from particles and the molecules were inclined to aggregate <i>via</i> the J-type mode. In addition, the aggregation process could be accelerated by raising the temperature proved by UV-Vis spectra. A molecular aggregation mechanism was proposed based on the experimental results.