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 o f optically active mixed, neutral-charged Pt/Pt and Pt/Pd macrocyclic complexes are described as well as the CD spectra of their correspondi ng precursors. Interaction between the chiral monomers (R(-)-DIOP or S (+)-DIOP) of cis-Pt(DIOP)(4-ethynylpyridine)(2) and the bistriflates o f 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 macrocyc les and their corresponding precursors reveal that the chiroptical pro perties are mainly determined by the BINAP moiety. The host-guest chem istry of the chiral 4-ethynylpyridine tetramers with silver triflate a nd the capture of neutral guests via the resulting square Lewis acid/b ase receptors have been monitored by CD.