Photoconversion of norbornadiene to quadricyclene in the presence of a copper(I) carbonyl compound

Article abstract of DOI:10.1021/ic50208a016

A detailed study of the thermal and photochemical behavior of Cu[HB(pz)₃](CO) [HB(pz)₃^- is hydrotris(1-pyrazolyl)borate] in the presence of norbornadiene (NBD) is reported. In solution NBD displaces CO from the coordination sphere of copper to produce a new complex formulated as Cu[HB(pz)₃](NBD). This ground-state process is readily discernible by a shift in the absorption spectrum of the system to longer wavelengths. Irradiation of the complex with 313-nm light induces the valence isomerization of norbornadiene to quadricyclene with high quantum efficiency. The occurrence of this pathway is explicable in terms of the bonding changes that result from populating an excited state possessing Cu-NBD charge-transfer character.