Spin-Selective Photoinduced Electron Transfer withinNaphthalenediimide Diradicals

There has been increasing interest in the excited states of stable diradicals as means of manipulating their spin states for potential applications in quantum information science (QIS). In this work, we examine a set of diradicals composed of two stable naphthalene-1,8:4,5-bis(dicarboximide) radical anions (NDI•–) bound either directly at their imide nitrogen atoms or through a series of benzene spacers resulting in diradicals with either singlet or triplet ground states. We use time-resolved near-UV, visible, near-IR, and mid-IR spectroscopy to show that the population in the singlet ground state can undergo photoinduced electron transfer upon excitation of one of the NDI•– radicals to produce the NDI0–NDI2– moiety, while the corresponding triplet population cannot. In particular, spectroscopy in the wavelength region 330–450 nm and in the energy range 1450–1750 cm–1 is critical to distinguishing the two populations. By varying the connectivity between the two radical anions, we vary both the sign and ma...