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 (VRuX, V=bisterpyridine, X=tetraterpyridine, Ru=Ruthenium) was initially used for the self-assembly of an anticipated hexagram upon reaction with Cd or Fe; however, unexpected pentagonal structures were formed, that is, [CdLA] and [FeLA]. In our redesign, LB [V(RuX)] was synthesized and treated with 60° V-shaped bisterpyridine (V) and Cd to create hexagonal hexagram [CdVLB] along with traces of the triangle [CdV]. Finally, a pure supramolecular hexagram [FeVLB] was successfully isolated in a high yield using Fe with a higher assembly temperature.