How does a double-cage single molecule confine an excess electron? Unusual intercage excess electron transfer...

To realize the chemistry of a multicage organic molecule with excess electron, as a model, by confining an excess electron inside a double-cage single molecule, the structures of e⁻@C₂₄F₂₂(NH)₂C₂₀F₁₈ (e⁻@AB) and e⁻@C₂₀F₁₈(NH)₂C₂₀F₁₈ (e⁻@BB') are obtained at the B3LYP/6-31G(d) + 4s4p theory level. It is confirmed that the excess electron is mainly confined inside one cage with larger interior electronic attractive potential (A for e⁻@AB and B for e⁻@BB') in the ground state, while the electron is localized in the other one in the first excited state. Owing to such excess electron localizations, an interesting intercage excess electron transfer transition takes places. This intercage excess electron transfer transition exhibits five characteristics: (1) the excess electron transfer from one cage to another (A → B for e⁻@AB and B → B' for e⁻@BB′'); (2) the transition is between the ground and first excited state; (3) the wavelength and strength are the largest; (4) the transition accompanies a significant charge transfer (Δq > 0.8) and molecular dipole moment change (Δμ > 20 D); (5) the transition corresponds to SOMO → LUMO. For the transition, the oscillator strength is larger and the wavelength is shorter for the asymmetric structure (e⁻@AB) than for the symmetric one (e⁻@BB'), which indicates that the intercage excess electron transfer transition may be regulated by changing the size of cage. This work is useful for the designs of organic electronic sponges (porous organic electrides), organic conductor with excess electrons, and photoelectric and nanoelectronic devices.