Abstract: A copolymer bearing norbornadiene and carbazole as pendants was synthesized and apolymer only having norbornadiene pendants was also prepared for comparision. The valenceisomerization of the norbornadiene molety to quadricy clane moiety proceeded smoothly when the two kinds of polymers were irradiated with the light below 350nm. If the wavelength ofthe incident light was above 350nm, the isomerization reaction was only found in copolymersystem. Utilizing fluorescence quenching experiment and CIDNP technique, the mechanismof sensitized valence isomerization was studied. The isomerization of quadricyclane moiety tonorbornadiene moiety was also achieved by using trifluoroacetic acid as catalyst.

Key words: norbornadiene, quadricyclane, photoinduced valence isomerization