Switchable Conformational Isomerization of an Overcrowded Tristricyclic Aromatic Ene (TAE).

We have prepared a new overcrowded tristricyclic aromatic ene (TAE) and investigated its external stimuli-responsive behavior for the interconversion between a closed-shell folded form and an open-shell twisted form. Upon photo-irradiation, the folded form transforms into the biradical twisted form, whereas by keeping the twisted form in the dark, the reverse reaction gradually occurs at room temperature. This switchable conformational change is analyzed by means of UV-Vis and ESR spectroscopies, cyclic voltammetry, density functional theory (DFT) calculations, and kinetic studies.

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