Trapping highly reactive photoinduced charge-transfer complex between amine and imide by light

Complexation between two organic molecules can occur either for strong electron donor-acceptor pairs in the ground state, known as charge-transfer complexes (CTCs), or for pairs of lesser strength in the excited state, such as excimers and exciplexes. However, the characterization of chemically distinct CTCs in solution remains elusive. Here, we report a light-induced, solution-persistent 1:1 CTC between an amine and an imide. The pair is not associated in the ground state at room temperature prior to light exposure. The presence and exact molecular compositions of the CTCs could be directly obtained from high-resolution mass spectrometry. Additional spectroscopic and computational evidence reveal that a kinetically trapped ground-state pair is formed following an exciplex-like process between the amine and the imide after photoexcitation. We show that such a photoinduced complex can be used to conduct photochemistry and store photon energy for producing otherwise photochromic products in the dark.