π-Conjugated organic compounds possess a wide range of tunable optoelectronic properties which make them promising materials for many semiconducting devices. These properties are dictated by their molecular structure and their supramolecular arrangement. While much efforts in the past decades have been put into tuning the molecular structure to achieve desired properties, rational supramolecular control remains a challenge. Here we induce significant modulation of HOMO/LUMO levels in a series of controllable supramolecular co-assemblies of polycyclic aromatic hydrocarbons via two-point hydrogen bonding. The hydrogen bonding interaction results in dramatic electronic perturbation of the molecular components leading to very strong charge transfer (CT) interactions in the weak donor-acceptor pairs. The resulting co-crystals displayed a low bandgap (Eg &lt; 1.5 eV) with intense CT absorption in the NIR region. Beyond this, we were able to detect significant temperature-dependent EPR signals and electrical conductivity for some co-crystals. Via details of DFT calculations, X-ray crystallographic analysis, absorptions, EPR spectroscopy, electrochemistry measurements and some electrical measurements, here we will uncover the structure-properties relationships in this new class of rationally designed organic charge transfer materials, in hope that our findings will serve as a stepping stone towards predictably-designed optoelectronics materials.

Dramatic enhancement of electron donor/acceptor ability by complementary hydrogen bonding

2019 Spring National Meeting

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