Complementary Hydrogen Bonding Modulates Electronic Properties and Controls Self-Assembly of Donor/Acceptor Semiconductors

A comprehensive investigation of the complementary H-bonding-mediated self-assembly between dipyrrolo[2,3-b:3,2-e]pyridine (P2P) electron donors and naphthalenediimide/perylenediimide (NDI/PDI) acceptors is reported. The synthesis of parent P2P and several aryl-substituted derivatives is described, along with their optical, redox, and single-crystal packing characteristics. The dual functionality of heteroatoms in the P2P/NDI(PDI) assembly, which act as proton donors/acceptors and also contribute to -conjugation, leads to H-bonding-induced perturbation of electronic levels. Concentration-dependent NMR and UV/Vis spectroscopic studies revealed a cooperative effect of H-bonding and - stacking interactions. This H-bonding-mediated co-assembly of donor (D) and acceptor (A) components leads to a new charge-transfer (CT) absorption that can be controlled throughout the visible range. The electronic interactions between D and A were further investigated by time-dependent DFT, which provided insights into the nature of the CT transition. Electropolymerization of difuryl-P2P afforded the first conjugated polymer incorporating H-bonding recognition units in its main chain.