Effect of Pyridyl Orientation on the Molecular Conformation and Self-Assembled Morphology of Regioisomeric Diketopyrrolopyrrole Derivatives

Abstract

We reported the synthesis, characterization, and self-assembly of two new regioisomeric π-conjugated chromophores (p-DBPy and d-DBPy) based on pyridyl-flanked diketopyrrolopyrrole (DPP), where the nitrogen atom in the pyridyl was proximal or distal to the central DPP unit. Their solid powders and solutions displayed different colors, especially for p-DBPy, which could be attributed to the conversion of molecular conformation and different intermolecular aggregations. UV–vis spectra demonstrated that the possible intermolecular hydrogen bonding existed in the solution of p-DBPy. Of particular interest is that the morphology of solid powders and thin films for each molecule investigated by SEM and AFM, respectively, were dramatically different owing to different intermolecular interactions and different crystal growth speed. Their spectroscopic and electrochemical properties turned out to be strongly dependent on the orientation of the pyridyl group. DFT calculations were performed to determine the optimize...