Fig. 1
From: Coulombic-enhanced hetero radical pairing interactions

Three types of π-electron interactions. a π–π interactions between two benzene rings, in the form of edge-to-face or parallel displaced stacking interactions. b Donor–acceptor interactions between TTF and NDI, as well as DNP and BPY2+. c Hom radial paring interactions between two identical radicals, including BPY+•, NDI─•, and TTF+•