The catalytic activity of cationic NHC-Zn II and NHC-Al III (NHC = N-heterocyclicc arbene) complexes in reactions that requiret he electrophilica ctivation of soft CÀC p bonds has been studied. The former proved able to act as a soft p-Lewis acid in av ariety of transformations. The benefit of the bulky IPr NHC ligand was demonstrated by comparison with simple ZnX 2 salts. The tested NHC-Al III catalysti s not able to activate CÀC p bonds but simple AlX 2 + ions were found potent in some cases. Scheme1.Nonclassical carbocation intermediatesi np-acid-catalyzed transformationso fenynes.

Following the case of tetrazines substituted with perfluorinated alkyl chains, separated by two methylene groups from the tetrazine core, a new series of analogous tetrazines, but featuring only one methylene group between the fluorescent core and the perfluorinated chain, have been synthesized, and their photo-physical properties investigated. Their fluorescence quantum yields in acetonitrile are in same range than chloroalkoxytetrazines, which make them interesting candidates for light emission. Surprisingly, the quantum yields are lower with one methylene group, rather than two methylene groups separating the fluorinated chain from the emitting core, in the case of unsymmetrical compounds, while they are superior in the case of symmetrical ones. This unusual observation is discussed in the article.

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