Precursor Control over the Self-Assembly of Organic Cages via Imine Condensation

A series of tetrahedral cages and
triangular prisms have been self-assembled
by condensing ostensibly analogous trisformyl precursors with tris
or bisamino linkers under the nominally reversible reaction conditions
in the manner of either [4 + 4] or [2 + 3], respectively. We observed
that the conformations of the trisformyl precursors have great impact
on the self-assembly pathway and product yields. More specifically,
a rigid and planar precursor favors the formation of prisms while
a more twisted one favors tetrahedron. As a comparison, a more flexible
precursor, which is able to adopt both relatively planar and twisted
conformations, is capable of producing both prisms and tetrahedrons
in relatively high yields. Both experimental and theoretical results
indicate that the self-assembly preference is ascribed to subtle variations
in the level of π–π and CH-π interactions
that act as the driving forces for the formation of prisms and tetrahedrons,
respectively.