A comparative IR and NMR study of two low-molecular-weight organogels (LMWGs) based on aminoacid derivatives let us point out the hierarchy of the gelation assembly process. Different association states of corresponding organogelator molecules can be observed leading to the supramolecular organization of gel. A first hydrogen bond network of gelators leads to the formation of "head-to-tail" stacking-up, which can be assembled afterward one to the other by π-π stacking interactions. These small supramolecular aggregates (incipient precursor) are still visible in NMR spectra, and they represent, for example, 36% of the total amount of gelator in the case of the L-phenylalanine derivative (gelator 1) at 1 wt % in toluene. Finally, in the last step, the incipient precursor tends to form the expected 3D fibrillar network responsible for the gelation phenomenon. Temperature-dependent IR and NMR experiments allowed us to identify these different states clearly.

Chromophoric probes of naphthalimide moieties enable evaluation of their assembling behaviour photophysically through fluorescence spectroscopy and microscopy, and circular dichroism. These experiments highlight the influence of the nature of the chemical substitution of the organogelator. Very interesting results were also obtained by performing CD experiments showing that the nature of the solvent should modify the chirality of self-assembled aggregates. Highly oriented network structures were observed in the gel state and disappeared in isotropic solution. Microfibrous self-aggregation of organogels is in situ observed via fluorescence and SHG imaging and confirmed by transmission electron microscopic analysis of the dried sample.

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