Sn-fused perylene diimides: Synthesis, mechanism, and properties

The first example of metal Sn-fused perylene diimides(PDI) derivative(Sn-PDI) was designed, synthesized, and investigated. To obtain this type compound, a simple one-pot synthesis, named stannylative cycloaddition reaction, has been successfully developed via a palladium-based catalyst system. The novel mechanism exhibits that the reaction experiences oxidative addition, Pd-cyclization, stannylation, Pd-Sn-cyclization, and reductive elimination processes successively. This stannylative cycloaddition does realize unique σ-π hyperconjugation effect and therefore significantly influencing on the photophysical, electrochemical and excited state properties. Compared with those of PDI, both of the absorption and fluorescence spectra of Sn-PDI display large red-shifts over 20 nm. The electron energy levels of Sn-PDI have changed with an uncommon regulation. And Sn-PDI gives a considerably raised highest occupied molecular orbital(HOMO) level of-6.00 eV More importantly, the singlet excitons of Sn-PDI could efficiently intersystem cross(ISC) into triplet state with a long lifetime of 17.8 μs, which is far longer than that(4.4 ns) of PDI.