Chiral molecular polygons based on the Pt-alkynyl linkage: Self-assembly, characterization, and functionalization

Treatment of 2,2′-diacetoxy-1,1′-binaphthyl-6,6′-bis(ethyne), L-H₂, with one equiv of trans-Pt(PEt₃)₂Cl₂ led to a mixture of different sizes of chiral metallocycles trans-(PEt₃)₂Pt(L)]_n (n = 3-8, 1-6). Each of the chiral molecular polygons 1-6 was purified by silica-gel column chromatography and characterized by ¹H, ¹³C{¹H}, and ³¹P{¹H} NMR spectroscopy, MS, IR, UV-Vis, and circular dichroism (CD) spectroscopies, size exclusion chromatography, and microanalysis. Chiral molecular square 2 was also characterized by single-crystal X-ray diffraction. The acetyl groups of 2 were readily deprotected under mild conditions to generate 2a which possesses exposed chiral dihydroxy functional groups. The dihydroxy groups were functionalized with n-octadecyl chains or Fréchet-type dendrons to generate dendritic molecules built on a chiral molecular square core. This work shows the potential of generating interesting functional supramolecular systems based on Pt-alkynyl chiral molecular polygons.