Mutual enrichment of the (photo)chemistry of sydnones and diarylethenes in their hybrids

Hybrids of mesoionic sydnone and photoswitchable diarylethene (SyDAEs) exhibited properties uncommon for either class of molecules. The mode of their (photo)chemical reactivity is determined by the size of the central ring unifying the two functional parts and the substituents in the fused benzene ring. SyDAEs based on six-membered ring are photoactive. In addition to photochromism, they undergo two novel irreversible oxidative reactions involving both functional parts. A SyDAE with seven-membered central ring is inactive under light but readily undergoes (3+2)-cycloaddition with diazacyclononyne provided by the favorable saddle-like conformation. Our results clearly demonstrate the benefit of constructing hybrid molecules for the further development of functional organic molecules.