A set of 5,15-biphenylene-bridged porphyrin wheels, namely, [n]cyclo-5,15-porphyrinylene-4,4′-biphenylenes [n]CPB, have been synthesized through the platination of 5,15-bis(4-(pinacolboranyl)phenyl) nickel(II) porphyrin and subsequent reductive elimination of PtII(cod)-bridged cyclic porphyrin intermediates. The calculated strain energies for CPB, CPB, CPB, and CPB are 49.3, 32.9, 23.5, and 16.0 kcal mol-1, respectively. UV/Vis absorption spectra and cyclic voltammetry indicated characteristic ring-size-dependent absorption-peak shifts and redox-potential shifts, which presumably reflect the degree of strain in the π-systems. Excitation-energy hopping (EEH) times were determined to be 5.1, 8.0, 8.0, and 9.6 ps for CPB, CPB, CPB, and CPB, respectively, in a pump-power-dependent TA experiment. Molecular wheels: A series of 5,15-biphenylene-bridged cyclic porphyrin arrays (see example; Ar=3,5-tBu2C6H3) were obtained by the platination of a 5,15-bis(4-pinacolateboryl)phenyl NiII porphyrin and subsequent reductive elimination of the PtII(cod)-bridged cyclic porphyrin intermediates. The 1H NMR and UV/Vis spectra, redox potentials, and intramolecular excitation-energy-hopping characteristics of the nanorings depend on the ring size.
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