Charge and Spin Transport in an Organic Molecular Square

Understanding electronic communication among multiple chromophoric and redox units requires construction of well-defined molecular architectures. Herein, we report the modular synthesis of a shape-persistent chiral organic square composed of four naphthalene-1,8:4,5-bis(dicarboximide) (NDI) sides and four trans-1,2-cyclohexanediamine corners. Single crystal X-ray diffraction reveals some distortion of the cyclohexane chair conformation in the solid state. Analysis of the packing of the molecular squares reveals the formation of highly ordered, one-dimensional tubular superstructures, held together by means of multiple [C-H...O=C] hydrogen-bonding interactions. Steady-state and time-resolved electronic spectroscopies show strong excited-state interactions in both the singlet and triplet manifolds. Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopies on the monoreduced state reveal electron sharing between all four NDI subunits comprising the molecular square.