indazole has the highest oscillator strength among the compounds that contain fragment c(cc)(c(c)c)n(C)n (Figure ). The maximum oscillator strength and ex-citation energy of the molecule are 1.430 and 5.381 eV, respectively. The highest intensity electron transition arises from the second-highest occupied MO (Figure ) to LUMO (Fig- ). The little overlap between the two orbitals suggests that a significant amount of electron density change is associated with the transition, which leads to strong absorption of light.