282. “Photochemical Study of [3₃](1,3,5)Cyclophane and Emission Spectral Properties of [3_n]Cyclophanes (n = 2-6)”
     Nogita, R.; Matohara, K.; Yamaji, M.; Oda, T.; Sakamoto, Y.; Kumagai, T.; Lim, C.; Yasutake, M.; Shimo, T.; Jefford, C.W.; Shinmyozu, T.
     J. Am. Chem. Soc. 2004, 126, 13732-13741.

The photochemical reaction of [3₃](1,3,5)cyclophane 2, which is a photoprecursor for the formation of propella[3₃]prismane 18, was studied using a sterilizing lamp (254 nm). Upon photolysis in dry and wet CH₂Cl₂ or MeOH in the presence of 2 mol/L aqueous HCl solution, the cyclophane 2 afforded novel cage compounds comprised of new skeletons, tetracyclo[6.3.1.0.^2,70^4,11]dodeca-5,9-diene 43, hexacyclo[6.4.0.0.^2,60.^4,110.^5,100^9,12]dodecane 44, and pentacyclo[6.4.0.0.^2,60.^4,110^5,10]dodecane 45. All of these products were confirmed by the X-ray structural analyses. A possible mechanism for the formation of these photoproducts via the hexaprismane derivative 18 is proposed. The photophysical properties in the excited state of the [3_n]cyclophanes ([3_n]CP, n = 2−6) were investigated by measuring the emission spectra and determining the quantum yields and lifetimes of the fluorescence. All [3_n]CPs show excimeric fluorescence without a monomeric one. The lifetime of the excimer fluorescence becomes gradually longer with the increasing number of the trimethylene bridges. The [3_n]CPs also shows excimeric phosphorescence spectra without vibrational structures for n = 2, 4, and 5, while phosphorescence is absent for n = 3 and 6. With an increase in symmetry of the benzene skeleton in the [3₃]- and [3₆]CPs, the probability of the radiation (phosphorescence) process from the lowest triplet state may drastically decrease.

DOI : 10.1021/ja030032x 

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