As previously mentioned, the most effective strategy for stabilizing the NDI radical involves the substitution of the imide axial positions or the NDI core with electron-withdrawing stabilizing groups. [37] [39] The presence of two highly aromatic conjugated DHP rings in the axial positions suggested the likelihood of radical formation. Upon irradiating a pale green solution of 1c (10 μM in DMF, purged with N2) with UV light (370 nm, 43 W), a significant alteration in absorption spectra was observed. The absorption maxima at 350 nm and 390 nm exhibited a decrease in intensity, while a gradual enhancement at 484 nm was observed over time (Figure ). The decrease in absorption maxima at 350 nm and 390 nm raised questions, considering that such changes typically occur during the opening of DHP units. However, the absence of a simultaneous change in the 649 nm band ruled out the possibility of DHP 1c→CPD 1o isomerization. This prompted further investigation into the underlying processes.