of the spirobifluorene skeleton. The energy gap induced by splitting for the HOMO is 0.11 eV, which is larger than that for the LUMO (0.05 eV) (Table ) but smaller than that forspirobifluorene (0.30 eV). The size of the orbitals around the spirocarbon in 2- [3] is relatively small, compared to that of spirobifluorene itself, which accounts for the relatively small spiroconjugation, and the same reasoning can be used to explain the similar tendency in 2-[4] and 2-[5], as described below. In the case of the 4-mer 2-[4], the HOMO and LUMO split 1: 2: 1 as shown in Figure , Figures and, and Table . The sign of orbitals around all of spirocarbon is mismatched with respect to each other in the HOMO, and matched with respect to each other in the HOMO-3 (Figure and Figure for schematic drawing). Since the number of a bifluorenyl units is even, the orbital signs around all of the spirocarbons are allowed to be matched in 2- [4]. This is in contrast to the case of 2- [3]. These results clearly suggest the effect of even and odd numbers of chromophore units in matching the sign of the orbitals. The splitting of LUMO in 2- [4] is quite small (0.01 eV), and LUMO to LUMO+3 are almost degenerate (Table ). In the case of the 5-mer 2- [5], the HOMO and LUMO of the bifluorenyl unit is split 1: 2: 2 as shown in Figure , Figure , Figure , and Table . The sign of the orbitals around all of the spirocarbons is mismatched with respect to each other in the HOMO, resulting in destabilization. As the number of bifluorenyl unit is odd, it is not possible to make the orbital signs around all of the spirocarbons match in the splitting for HOMO of the bifluorenyl unit in 2- [5]. Similar to the 3-mer and 4-mer, splitting of the LUMO (0.02 and 0.03 eV) is small compared to that of HOMO (0.04 and 0.09 eV) (Table ).