The dissymmetry factors |glum| were 1.9 x 10 -3 at 348 nm, 8.5 x 10 -3 at 346 nm, and 1.9 x 10 -3 at 363 nm for the 3-mer, 4-mer, and 5-mer, respectively. The values for the 3-mer and 5-mer are comparable to that for the linear [3]spirobifluorenylene 1 and most of the other chiral small organic molecules listed in a recent review. The value for the dissymmetry factor of the 4-mer was higher to them. A large |glum| factor with a high ϕPL yield is desireble for practical photonics applications. Thus, the 4-mer with a 93% ϕPL yield can be considered to be a potential candidate. Spiroconjugation involves through-space interactions of the p-orbitals around the spirocarbon. In the case of the spirobifluorene, for example, the through-space interactions of the porbitals of HOMO for a fluorene unit induces the splitting of HOMO in the spirobifluorene, whereas, the LUMO degenerates because of the symmetry of the orbitals (Figure ). In contrast, the the number of bifluorenyl units is odd (Figure ). In contrast, the splitting of the LUMO of the bifluorenyl unit results in a stabilized MO and two destabilized doubly degenerate MOs. Considering the symmetry of the LUMO in the bifluorenyl unit, the LUMO of 2- [3] would be expected to be triply degenerate, which is similar to the doubly degenerate LUMO of spirobifluorene itself (Figure ).