1D Supramolecular Assemblies That Crystallize and Form Gels in Response to the Shape-Complementarity of Alcohols

N-9-Fluorenylmethyloxycarbonyl (Fmoc)-
and C-tertiary butyl (t-Bu)-protected
glutamate
(L-2), bearing a phenanthroline moiety at the side residue,
forms 1D supramolecular assemblies via H-bonding as well as undergoing
π-stacking interactions to afford crystals or gels that depend
on the shape-complementarity of coexisting alcohols, as demonstrated
by structural analyses on these assemblies by means of single-crystal
X-ray diffractometry and supplemented with small- and wide-angle X-ray
scattering data. Moreover, the rheological measurements on the gels
help to define a model for when gels and crystals are expected and
found. These observations and conclusions highlight an important,
but not very appreciated, aspect of solute–solvent interactions
within supramolecular assemblies that can allow the constituent-aggregating
molecules in some systems to exhibit high selectivity toward the structures
of their solvents. The consequences of this selectivity, as demonstrated
here by single-crystal and powder X-ray diffraction data, can lead
to self-assembled structures which alter completely the bulk phase
properties and morphology of the materials. In that regard, rheological
measurements have helped to develop a model to explain when gels and
phase-separated mixtures of crystals and solvents are expected.