(A) Molecular structures of 1, 2, and 3. (B) Gas-phase highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies of 1, 2, and 3 (in hartree). (C) HOMOs (first four) and LUMOs (last three) of 1 (C), 2 (D), and 3 (E).