Author: ["Daishi Fujita","Yoshihiro Ueda","Sota Sato","Nobuhiro Mizuno","Takashi Kumasaka","Makoto Fujita"]
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Abstract
Graph theory is used to guide the self-assembly of a complex consisting of 48 palladium ions and 96 ligands, with the topology of a tetravalent Goldberg polyhedron. Rational control of self-assembly remains a formidable challenge. It is thought to become increasingly difficult, even impossible, as the number of individual constituents increases. For example, no one has ever been able to design discrete molecules that self-assemble from more than 100 components. When exploring design principles appropriate for dealing with the self-assembly of large numbers of components, Daishi Fujita et al. discovered a spherical structure with a topology not previously reported at the molecular level. Using mathematics describing this class of structures, the authors then targeted and characterized an even larger structure containing 48 palladium ions coordinated by 96 bent organic ligands—by far the largest number of components observed in a self-assembled molecular structure to date. The structure has the topology of a tetravalent Goldberg polyhedron, a type of convex polyhedron made from squares and triangles—a twist on the original Goldberg polyhedra that were first described by Michael Goldberg in 1937. Rational control of the self-assembly of large structures is one of the key challenges in chemistry1,2,3,4,5,6,7,8,9, and is believed to become increasingly difficult and ultimately impossible as the number of components involved increases. So far, it has not been possible to design a self-assembled discrete molecule made up of more than 100 components. Such molecules—for example, spherical virus capsids10—are prevalent in nature, which suggests that the difficulty in designing these very large self-assembled molecules is due to a lack of understanding of the underlying design principles. For example, the targeted assembly of a series of large spherical structures containing up to 30 palladium ions coordinated by up to 60 bent organic ligands11,12,13,14,15,16 was achieved by considering their topologies17. Here we report the self-assembly of a spherical structure that also contains 30 palladium ions and 60 bent ligands, but belongs to a shape family that has not previously been observed experimentally17. The new structure consists of a combination of 8 triangles and 24 squares, and has the symmetry of a tetravalent Goldberg polyhedron18,19. Platonic and Archimedean solids have previously been prepared through self-assembly, as have trivalent Goldberg polyhedra, which occur naturally in the form of virus capsids20 and fullerenes21. But tetravalent Goldberg polyhedra have not previously been reported at the molecular level, although their topologies have been predicted using graph theory. We use graph theory to predict the self-assembly of even larger tetravalent Goldberg polyhedra, which should be more stable, enabling another member of this polyhedron family to be assembled from 144 components: 48 palladium ions and 96 bent ligands.Cite this article
Fujita, D., Ueda, Y., Sato, S. et al. Self-assembly of tetravalent Goldberg polyhedra from 144 small components. Nature 540, 563–566 (2016). https://doi.org/10.1038/nature20771 