Self-assembly of a supramolecular hexagram and a supramolecular pentagram

Five- and six-pointed star structures occur frequently in nature as flowers, snow-flakes, leaves and so on. These star-shaped patterns are also frequently used in both functional and artistic man-made architectures. Here following a stepwise synthesis and self-assembly approach, pentagonal and hexagonal metallosupramolecules possessing star-shaped motifs were prepared based on the careful design of metallo-organic ligands (MOLs). In the MOL design and preparation, robust ruthenium–terpyridyl complexes were employed to construct brominated metallo-organic intermediates, followed by a Suzuki coupling reaction to achieve the required ensemble. Ligand LA (VRu(2+)X, V=bisterpyridine, X=tetraterpyridine, Ru=Ruthenium) was initially used for the self-assembly of an anticipated hexagram upon reaction with Cd(2+) or Fe(2+); however, unexpected pentagonal structures were formed, that is, [Cd(5)LA(5)](30+) and [Fe(5)LA(5)](30+). In our redesign, LB [V(Ru(2+)X)(2)] was synthesized and treated with 60° V-shaped bisterpyridine (V) and Cd(2+) to create hexagonal hexagram [Cd(12)V(3)LB(3)](36+) along with traces of the triangle [Cd(3)V(3)](6+). Finally, a pure supramolecular hexagram [Fe(12)V(3)LB(3)](36+) was successfully isolated in a high yield using Fe(2+) with a higher assembly temperature.