Barrier photodimerization

The CASPT2 results on the photodimerization of two cytosine molecules taking place along the triplet manifold are compiled in Figure 16-14. As can be deduced from this figure that the MEP computations from 3(LE) lead directly to the triplet step-wise intermediate 3(SWI) with out any energy barrier. This intermediate (3(SWI)) is characterized by the formation of a single covalent bond... 

Energy barriers due to restrictive ligand fields can, in theory, be circumvented in other ways. Perhaps the most interesting involves the use of photons to generate nonrestrictive. Type II systems from restrictive Type I systems. Photodimerization of norbornadiene to cyclobutane products as-... 

Figure 6.17. Schematic correlation diagram for photodimerization, showing the crossing (f) that determines the barrier between excimer minimum (E ) and peri-cyclic minimum (P ), an earlier crossing (—), and a later crossing ) (by permission from Caldwell, 1980). Effects of a likely diagonal distortion are not shown.

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