Synthesis of Oxacalixarene-Locked Bisporphyrins and Higher Oligomers

The efficient one-step synthesis of oxacalixarene-bisporphyrins and higher oligomers from readily available starting materials is described. The X-ray structure of one oxacalix[4]arene-locked cofacial bisporphyrin, prepared in 91% yield, shows an 1,3-alternate conformation of the molecule with partial overlap of the two porphyrin rings. 1H NMR data supports a similar conformation in solution. The absorption and emission spectra of oxacalixarene-porphyrins are briefly discussed.