Design of Carbon–Carbon Ylides

Here, we have reported the computational design of a new class of ylides, elusive carbon-carbon ylides featuring zwitterionic σ-bonds, derived from the norbornane-2,6-dione framework. Utilizing the state-of-the-art computational methods, we have demonstrated that appropriate substitutions on this scaffold can stabilize a carbanion at C1 and a carbocation at C7 without orbital overlap, ensuring a zwitterionic electronic structure akin to a CC-ylide. Large singlet-triplet energy gaps guarantee that these species do not adopt a diradical ground state. Time-dependent DFT computations further have revealed small T1-S1 energy gaps, suggesting potential applications of similar scaffolds in thermally activated delayed fluorescence (TADF) materials. Our analyses have identified the cation on C7 as the most reactive site on the molecule toward unwanted reactions, leading to the degradation of the ylides. With their unique electronic structure, CC-ylides present new opportunities for unexplored chemical reactivity and functional material design.