Journal of the American Chemical Society, Vol.120, No.38, 9827-9837, 1998
Self-assembly, chiroptical properties, and host-guest chemistry of chiral Pt-Pt and Pt-Pd tetranuclear macrocycles. Circular dichroism studies on neutral guest inclusion phenomena
The synthesis, characterization, and circular dichroism (CD) spectra of optically active mixed, neutral-charged Pt/Pt and Pt/Pd macrocyclic complexes are described as well as the CD spectra of their corresponding precursors. Interaction between the chiral monomers (R(-)-DIOP or S(+)-DIOP) of cis-Pt(DIOP)(4-ethynylpyridine)(2) and the bistriflates of chiral (R(+)-BINAP or S(-)BINAP)) Pt(II) or Pd(II) bisphosphines or cis-Pd(PEt3)(2)(OSO2CF3)(2), in CH2Cl2 at room temperature results in the formation of cyclic, chiral molecular squares in 84-99% yields via self-assembly. CD studies and optical rotation of the chiral macrocycles and their corresponding precursors reveal that the chiroptical properties are mainly determined by the BINAP moiety. The host-guest chemistry of the chiral 4-ethynylpyridine tetramers with silver triflate and the capture of neutral guests via the resulting square Lewis acid/base receptors have been monitored by CD.
Keywords:IODONIUM-TRANSITION-METAL, AXIALLY DISSYMMETRIC MOLECULES;STATE-INDUCED TRANSFORMATIONS, ALUMINUM-HYDRIDE REAGENTS, RAYCRYSTAL-STRUCTURE, FUNCTIONALIZED 2;6-OLIGOPYRIDINES, HELICALCOMPLEXES, AQUEOUS-MEDIA, ENANTIOSELECTIVE REDUCTION;SUPRAMOLECULAR CHEMISTRY