4CzIPN is significantly slower and less efficient in this isomerization reaction, producing a steady-state E/Z ratio of only 69/31 ± 4 after 24 h (Table , Entry 12); indeed, after 4 hours there is only an E/Z ratio of 95/5 ± 1 (Table ). Under these conditions, 4CzIPN is photostable under N2, though in air photodegradation of 4CzIPN is observed (Figure ). Thus, the poor performance of 4CzIPN can be explained by the too-small spectral overlap with the fumarate substrate.