Synthesis and Emergent Photophysical Properties of Diketopyrrolopyrrole-Based Supramolecular Self-Assembly

Diketopyrrolopyrrole (DPP)-based molecular semiconductors exhibit intriguing optical and charge transport properties. Herein, we rationally design a series of electronically identical but structurally distinct Hamilton receptor (HR)-based supramolecular assembly of DPP. The HR endows supramolecular assemblies via hydrogen bonding with enhanced structural ordering and excitonic couplings. The mechanism of supramolecular self-assembly was probed by diffusion ordered spectroscopy (DOSY) nuclear magnetic resonance (NMR) and solid-state IR spectroscopy studies. We investigated the morphology of self-assembly, photophysical and electrochemical properties and compared them with the identical DPP molecular structures without HRs. The microstructure of self-assembly was probed with atomic force microscopy in thin films. Subsequently, the influence of solid-state packing was studied by single-crystal X-ray diffraction. The single-crystal structure of HR-TDPP-C-20 reveals slipped stack arrangements between the two neighboring chromophores with pi-pi stacking distance and slip angle of 3.55 angstrom and 35.4 degrees, respectively. Notably, the slight torsional angle of 1 degrees between thiophene and lactam rings and small pi-pi stacking distance suggest a significant intermolecular coupling between thiophene (D) and lactam (A) rings. This intramolecular coupling between two pi-pi chromophore stacks manifests in their optical properties. In this manuscript, we report rational design and synthesis of supramolecular self-assembly of DPP with a collection of compelling structural and optical properties.

Automated summary

In this study, a series of structurally distinct supramolecular assemblies of DPP based on Hamilton receptors (HRs) were designed and synthesized, which exhibited enhanced structural ordering and excitonic couplings through hydrogen bonding. The self-assembly mechanism was investigated using spectroscopy and solid-state IR spectroscopy. The morphology, photophysical and electrochemical properties of the self-assemblies were studied and compared with DPP molecular structures without HRs. The crystal structure analysis revealed slipped stack arrangements and intermolecular coupling between thiophene and lactam rings, leading to interesting optical properties.