Département de chimie moléculaire

The synthesis, full characterization, photoredn. properties, and catalytic activity for the copper(I)-catalyzed alkyne-azide cycloaddn. (CuAAC) reaction of a copper(II)-DMEDA (N,N'-dimethylethylendiamine) complex is reported. Spectroscopic studies (UV/Vis, EPR) demonstrated that under daylight illumination highly effective copper(II) to copper(I) redn. occurs in this complex. These findings are in agreement with a high photoredn. quantum yield value of 0.22 in MeOH, and a value approaching unity as detd. in THF. The redn. process, which can also be conducted by irradn. at 365 nm by using a std. TLC (thin layer chromatog.) lamp, is ascribed to a highly efficient photoinduced electron transfer (PET) process mediated by the benzophenone photosensitizer present in the carboxylate counterion. Having deaerated the reaction mixt., the photogenerated copper(I) species proved to be highly active for the CuAAC reaction, demonstrated by reactions conducted with low catalyst loading (0.5 mol {%}) on a range of clickable protected and non-protected mono- and disaccharides. Once initiated, the reaction can be stopped at any time on introducing air into the reaction medium. Deoxygenation followed by irradn. restores the activity, making the copper(II)-DMEDA complex a switchable catalyst of practical value. [on SciFinder(R)]