Yin-Feng Wang

Excess electron is trapped in a large single molecular cage C60F60

A new kind of solvated electron systems, sphere‐shaped e−@C60F60 (Ih) and capsule‐shaped e−@C60F60 (D6h), in contrast to the endohedral complex M@C60, is represented at the B3LYP/6‐31G(d) + dBF (diffusive basis functions) density functional theory. It is proven, by examining the singly occupied molecular orbital (SOMO) and the spin density map of e−@C60F60, that the excess electron is indeed encapsulated inside the C60F60 cage. The shape of the electron cloud in SOMO matches with the shape of C60F60 cage. These cage‐like single molecular solvated electrons have considerably large vertical electron detachment energies VDE of 4.95 (Ih) and 4.67 eV (D6h) at B3LYP/6‐31+G(3df) + dBF level compared to the VDE of 3.2 eV for an electron in bulk water (Coe et al., Int Rev Phys Chem 2001, 20, 33) and that of 3.66 eV for e−@C20F20 (Irikura, J Phys Chem A 2008, 112, 983), which shows their higher stability. The VDE of the sphere‐shaped e−@C60F60 (Ih) is greater than that of the capsule‐shaped e−@C60F60 (D6h), indicating that the excess electron prefers to reside in the cage with the higher symmetry to form the more stable solvated electron. It is also noticed that the cage size [7.994 (Ih), 5.714 and 9.978 Å (D6h) in diameter] is much larger than that (2.826 Å) of (H2O)20− dodecahedral cluster (Khan, Chem Phys Lett 2005, 401, 85).

Quantum mechanical design and structures of hexanuclear sandwich complex and its multidecker sandwich clusters (Li6)n([18]annulene)n+1 (n = 1-3).

By means of density functional theory, a hexanuclear sandwich complex [18]annulene-Li6-[18]annulene which consists of a central Li6 hexagon ring and large face-capping ligands, [18]annulene, is designed and investigated. The large interaction energy and HOMO-LUMO gap suggest that this novel charge-separated complex is highly stable and may be experimentally synthesized. In addition, the stability found in the [18]annulene-Li6-[18]annulene complex extends to multidecker sandwich clusters (Li6)n([18]annulene)n+1 (n = 2-3). The energy gain upon addition of a [18]annulene-Li6 unit to (Li6)n-1([18]annulene)n is pretty large (96.97-98.22 kcal/mol), indicating that even larger multideckers will also be very stable. Similar to ferrocene, such a hexanuclear sandwich complex could be considered as a versatile building block to find potential applications in different areas of chemistry, such as nanoscience and material science.

Evolution of lone pair of excess electrons inside molecular cages with the deformation of the cage in e2@C60F60 systems

For unusual e2@C60F60 (Ih, D6h, and D5d) cage structures with two excess electrons, it is reported that not only the lone pair in singlet state but also two single excess electrons in triplet state can be encapsulated inside the C60F60 cages to form single molecular solvated dielectrons. The interesting relationship between the shape of the cage and the spin state of the system has revealed that ground states are singlet state for spherical shaped e2@C60F60 (Ih) and triplet states for short capsular shaped e2@C60F60 (D6h) and long capsular shaped e2@C60F60 (D5d), which shows a spin evolution from the singlet to triplet state with the deformation of the cage from spherical to capsular shape. For these excess electron systems, the three ground state structures have large vertical electron detachment energies (VDEs (I) of 1.720–2.283 eV and VDEs (II) of 3.959–5.288 eV), which shows their stabilities and suggests that the large C60F60 cage is the efficient container of excess electrons.

Intercage electron transfer driven by electric field in Robin-Day-type molecules.

A new class of isomers, namely, intercage electron-transfer isomers, is reported for fluorinated double-cage molecular anion e(-)@C(20)F(18)(NH)(2)C(20)F(18) with C(20)F(18) cages: 1 with the excess electron inside the left cage, 2 with the excess electron inside both cages, and 3 with the excess electron inside the right cage. Interestingly, the C(20)F(18) cages may be considered as two redox sites existing in a rare nonmetal mixed-valent (0 and -1) molecular anion. The three isomers with two redox sites may be the founding members of a new class of mixed-valent compounds, namely, nonmetal Robin-Day Class II with localized redox centers for 1 and 3, and Class III with delocalized redox centers for 2. Two intercage electron-transfers pathways involving transfer of one or half an excess electron from one cage to the other are found: 1) Manipulating the external electric field (-0.001 a.u. for 1→3 and -0.0005 a.u. for 1→2) and 2) Exciting the transition from ground to first excited state and subsequent radiationless transition from the excited state to another ground state for 1 and 3. For the exhibited microscopic electron-transfer process 1→3, 2 may be the transition state, and the electron-transfer barrier of 6.021 kcal mol(-1) is close to the electric field work of 8.04 kcal mol(-1).