Anion-induced electron transfer (ET) to π-electron-deficient naphthalenediimides (NDIs) can be channeled through two distinct pathways by adjusting the Lewis basicity of the anion and the π-acidity of the NDI: (1) When the anion and NDI are a strong electron donor and acceptor, respectively, positioning the HOMO of the anion above the LUMO of the NDI, a thermal anion → NDI ET pathway is turned ON. (2) When the HOMO of a weakly Lewis basic anion falls below the LUMO of an NDI but still lies above its HOMO, the thermal ET is turned OFF, but light can activate an unprecedented anion → 1*NDI photoinduced ET pathway from the anion's HOMO to the photogenerated 1*NDI's SOMO-1. Both pathways generate NDI •- radical anions. © 2011 American Chemical Society.