Photochemical conversion of norbornadiene into quadricyclane in the presence of acridinone-type sensitizers
den Ouden, B.
Instituut voor Toegepaste Chemie TNO
In this study, a series of acridinones and benzo-fused acridinones have been used for the first time as efficient photosensitizers for the norbornadiene-quadricyclane isomerization by near UV and visible iradiation. Their triplet energies (240-280 kJ · Mol-1) are well below the value of 290 kJ · Mol-1 which is generally assumed for norbornadiene. A mechanism is postulated involving an exciplex between sensitizer and norbornadiene. Limiting quantum yields of 0.5 and higher have been determined for this valence isomerization extrapolated to infinite norbornadiene concentration. Exciplex formation is supported by measurements of the rate of constant k2 for quenching of excited sensitizer by norbornadiene, yielding values which are much smaller than the diffusion-controlled quenching constant.
To reference this document use:
Recueil des Travaux Chimiques des Pays-Bas, 104 (4), 109-116