Abstract: Photochemical valence isomerization of bicyclo [2. 2. 1] -2, 3 -dicarboxy -2, 5 -heptadiene (N) to quadrocyclo[2.2.1.0^2,3. 0^5,6]-2, 3 - dicarboxy heptane (Q) was performed by using polytetraphenyl-porphrine(P-TPP)as sensitizer. In addition, The Q can be easily converted into N under the presence of catalyst, Cobalt (Ⅱ) polytetraphenylpor-phrine (Co-P-TPP). The effects of the sensitizer and the catalyst on these isomerization reaction were tested. The comparation between the excited state energy of P - TPP and N indicated that photochemical valence isomerization may go by way of electron transfer from P-TPP to N. The support for the electron transfer machenism is fluorescence quenching of P-TPP by N.

Key words: valence isomerization, photosensitized reaction, polytetraphenylpor-phrine, bicyclo[2.2.1]-2,3-dicatboxy-2,5-heptadiene