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 pi-pi and CH-pi interactions that act as the driving forces for the formation of prisms and tetrahedrons, respectively.