From 1 → 3 dendritic designs to fractal supramacromolecular constructs: understanding the pathway to the Sierpiński gasket.

Abstract

The iterative synthetic protocols used for dendrimer construction were developed based on the desire to easily craft highly branched macromolecules with ideally an exact mass and tailored functionality. Inspired by arboreal design and precursors of the utilitarian macromolecules known as dendrimers today, our first examples employed predesigned, 1 → 3 or 1 → (1 + 2) C-branched, building blocks. Physical characteristics of the dendrimers, including their globular shapes, excellent solubility, and demonstrated aggregation, revealed the inherent supramolecular potential. The architecture that is characteristic of dendritic materials also exhibits obvious fractal qualities based on self-similar, repetitive, branched frameworks. Thus, both the fractal design and supramolecular aspects of these constructs are suggestive of a larger field of fractal materials that incorporate repeating geometries and are derived by complementary building block recognition and assembly. Use of 〈terpyridine-M(2+)-terpyridine〉 connectivity for the sides and tuned directed organic vertices has opened the door to other types of novel materials. This approach also circumvents the nonideality of dendrimers, since the heteroleptic, one-step, spontaneous self-assembly process facilitates quantitative outcomes.