Abstract
Macrocyclic and medium size stilbenophanes tethered by silyl chains were synthesized, and their photochemical properties were examined. Direct photoirradiation of a macrocyclic compound having two stilbene units and four dimethylsilyl groups in the ring gave intramolecular photocycloadduct stereoselectively, while triplet-sensitized photoreaction caused cis-trans photoisomerization of the stilben units. Photoreaction of cis-fixed medium size stilbenophanes under oxygen atmosphere gave the corresponding phenanthrenophanes. Absorption maxima of these stilbenophanes appeared at about 326 nm in dichloromethane, whose values were shifted to longer wavelength than that of unsubstituted trans-stilbene. Fluorescence quantum yield of the macrocyclic stilbenophane was larger than that of 4,4'-bis(trimethylsilylmethyl)stilbene. X-ray crystallographic analysis of the macrocyclic stilbenophane showed partially loss pf planarity of the stilbene units. The distance between two stilbene double bonds is about 7 angstrom, and the two stilbene units align like stairs.
