Abstract
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 (VRu2+X, V=bisterpyridine, X=tetraterpyridine, Ru=Ruthenium) was initially used for the self-assembly of an anticipated hexagram upon reaction with Cd2+ or Fe2+; however, unexpected pentagonal structures were formed, that is, [Cd5LA5]30+ and [Fe5LA5]30+. In our redesign, LB [V(Ru2+X)2] was synthesized and treated with 60° V-shaped bisterpyridine (V) and Cd2+ to create hexagonal hexagram [Cd12V3LB3]36+ along with traces of the triangle [Cd3V3]6+. Finally, a pure supramolecular hexagram [Fe12V3LB3]36+ was successfully isolated in a high yield using Fe2+ with a higher assembly temperature.
Highlights
Five- and six-pointed star structures occur frequently in nature as flowers, snow-flakes, leaves and so on
Using Fe2 þ cations with strong coordination, we observed the formation of a mixture of small triangle, bowtie-like double-triangle and triple-triangle along with a small amount of unidentified metallo-polymer due to the self-sorting of polyterpyridines with metal ions (Fig. 2; Supplementary Information)
A trace amount of triple-triangle [Fe9V5X2]18 þ was only characterized with electro-spray ionization mass spectrometry (ESI-MS) (Supplementary Figs 15 and 16) to confirm the proposed structure
Summary
Five- and six-pointed star structures occur frequently in nature as flowers, snow-flakes, leaves and so on. Supramolecular self-assembly and recognition have become appealing in recent years on scales ranging from relatively small and simple structures to complex, highly ordered architectures[1] Garnering much of this attention, Lehn[2,3], Stang[4,5], Stoddart[6,7], Fujita[8,9,10,11,12,13], Raymond[14,15], Newkome[16,17,18,19], Leigh[20,21,22,23,24,25], Nitschke[26,27,28,29] and others[30,31,32,33] have designed and constructed numerous unprecedented metallo-architectures with precisely geometry controlled by using predesigned organic ligands through self-assembly procedures. We present the synthesis and self-assembly of planar supramolecular pentagram and hexagram structures, using precisely predesigned tpy-based metallo-organic ligands (MOLs)
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