From C-C bond cleavage to fluorescence: cyclic (alkyl)(amino)carbene-driven activation of 1,2-diketones

We report that cyclic (alkyl)(amino)carbenes (CAACs) mediate the selective C-C bond cleavage of 1,2-diketones, thereby establishing reaction-driven structural reorganization as a strategy for creating luminescent aluminum complexes. Leveraging the ambiphilicity of CAACs, nucleophilic attack followed by intramolecular electronic redistribution triggers selective C-C bond cleavage. Subsequent stoichiometric control of AlCl₃ enables the formation of mononuclear (1-Al1) and dinuclear (1-Al2) aluminum complexes. While 1 and 1-Al1 are non-emissive, 1-Al2 exhibits a pronounced fluorescence switch-on at 540 nm. Combined experimental and computational analyses reveal that fluorescence quenching in 1-Al1 arises from state inversion and global structural distortion, whereas 1-Al2 suppresses structural relaxation through framework rigidification, resulting in a fluorescence lifetime of 10.5 ns. This work establishes carbene-mediated C-C bond activation as a reaction-driven molecular design strategy for the development of luminescent aluminum complexes.