Photochemical anti–syn isomerization around the –N–N bond in heterocyclic imines

Abstract

Irradiation with UV light (365 nm) leads to photochemically-induced isomerization from the anti- to the higher-energy syn-form around the –N–N linkage.

A study of the photochemical behaviour and relaxation mechanisms of anti–syn isomerisation around quinazolinone –N–N bonds

“…The photochemical process in quinazolinones proceeds at the –N–NC(H) array (in contrast to the NN bond analysed in azobenzene 41,42 and its derivatives 43,44 ), which is part of a large π-system including a lone electron pair in the sp 2 -hybridised orbital of the nitrogen atom of the azomethine group. As shown previously, 45,46 photoisomerisation specifically proceeds around the N–N linkage in the –N–NC(H) atom array in quinazolinones.…”

“…4. The calculated energies for both isomers of 1-7, together with the previously published data for structure 8, 46 are shown in Table 5. The anti-form is more stable in all cases, in agreement with NMR experiments.…”

“…The functional uB97X-D was employed in all types of calculations as it was previously found suitable for calculating similar organic systems. 45,46 The convergence criteria were set to tight, using an ultrane integration grid, for the main calculations of the syn/ anti structures and energies (Tables 5 and 6); loose or default convergence criteria, and default integration grid, were used for data in other tables. Use of the default grid introduces small errors to the calculated energies; see ESI, Section S2.2, † for discussion.…”

“…Rotation around the N-N bond leads to formation of two conformers for this systems as well (anti and syn), in agreement with NMR experiments and in accordance with our evidence. 45,46 3.2.2. Study of mechanisms.…”

One-pot multicomponent green LED photoinduced synthesis of chromeno[4,3-b]chromenes catalyzed by a new nanophotocatalyst histaminium tetrachlorozincate

“…Therefore, chemists have promoted photochemical reactions as an interesting led in organic synthesis. [8][9][10] Among many advantages of photochemical reactions, traditional UV light sources have signicant drawbacks including various technical complications, energy intensive nature, limited lifetime and considerable requirements due to dissipation of heat generated from the light source. In addition, the energy of a UV photon is generally in the range of carbon-carbon s bonds, which induces problematic complications and may result in various unwanted photo induced decomposition reactions and the generation of obscure optical polymeric materials on the reactor wall.…”