Impact of Hydrophobic/Hydrophilic Balance on Aggregation Pathways, Morphologies, and Excited-State Dynamics of Amphiphilic Diketopyrrolopyrrole Dyes in Aqueous Media

• Published in: Journal of the American Chemical Society Vol. 144; no. 49; pp. 22479 - 22492
• Main Authors: Fukaya, Natsumi, Ogi, Soichiro, Sotome, Hikaru, Fujimoto, Kazuhiro J., Yanai, Takeshi, Bäumer, Nils, Fernández, Gustavo, Miyasaka, Hiroshi, Yamaguchi, Shigehiro
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 14.12.2022; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Multidisciplinary; Coloring Agents; Hydrophobic and Hydrophilic Interactions; Kinetics; Physical Sciences; Science & Technology; Water - chemistry; MOLECULAR DESIGN; POLYMERS; ENERGY; PHOTODYNAMIC THERAPY; MECHANISM; COMPLEXITY; PHOTOSENSITIZERS; LIVING SUPRAMOLECULAR POLYMERIZATION; 2ND-ORDER PERTURBATION-THEORY; CONONSOLVENCY
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.2c07299

We report the thermodynamic and kinetic aqueous self-assembly of a series of amide-functionalized dithienyldiketopyrrolopyrroles (TDPPs) that bear various hydrophilic oligoethylene glycol (OEG) and hydrophobic alkyl chains. Spectroscopic and microscopic studies showed that the TDPP-based amphiphiles with an octyl group form sheet-like aggregates with J-type exciton coupling. The effect of the alkyl chains on the aggregated structure and the internal molecular orientation was examined via computational studies combining MD simulations and TD-DFT calculations. Furthermore, solvent and thermal denaturation experiments provided a state diagram that indicates the formation of unexpected nanoparticles during the self-assembly into nanosheets when longer OEG side chains are introduced. A kinetic analysis revealed that the nanoparticles were obtained selectively as an on-pathway intermediate state toward the formation of thermodynamically controlled nanosheets. The metastable aggregates were used for seed-initiated supramolecular assembly, which allowed establishing control over the assembly kinetics and the aggregate size. The sheet-like aggregates prepared using the seeding method exhibited coherent vibration in the excited state, indicating a well-ordered orientation of the TDPP units. These results underline the significance of fine tuning of the hydrophobic/hydrophilic balance in the molecular design to kinetically control the assembly of amphiphilic π-conjugated molecules into two-dimensional nanostructures in aqueous media.