title: J-aggregation, its impact on excited state dynamics and unique solvent effects on macroscopic assembly of a core-substituted naphthalenediimide.
abstract: Herein we reveal a straightforward supramolecular design for the H-bonding driven J-aggregation of an amine-substituted cNDI in aliphatic hydrocarbons. Transient absorption spectroscopy reveals sub-ps intramolecular electron transfer in isolated NDI molecules in a THF solution followed by a fast recombination process, while a remarkable extension of the excited state lifetime by more than one order of magnitude occurred in methylcyclohexane likely owing to an increased charge-separation as a result of better delocalization of the charge-separated states in J-aggregates. We also describe unique solvent-effects on the macroscopic structure and morphology. While J-aggregation with similar photophysical characteristics was noticed in all the tested aliphatic hydrocarbons, the morphology strongly depends on the "structure" of the solvents. In linear hydrocarbons (n-hexane, n-octane, n-decane or n-dodecane), formation of an entangled fibrillar network leads to macroscopic gelation while in cyclic hydrocarbons (methylcyclohexane or cyclohexane) although having a similar polarity, the cNDI exhibits nanoscale spherical particles. These unprecedented solvent effects were rationalized by establishing structure-dependent specific interactions of the solvent molecules with the cNDI which may serve as a general guideline for solvent-induced morphology-control of structurally related self-assembled materials.
authors: Polymer Science Unit, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata, India-700032. psusg2@iacs.res.in.
authors: Haridas
authors: H
authors: Kar
authors: Dominik W
authors: DW
authors: Gehrig
authors: Frédéric
authors: F
authors: Laquai
authors: Suhrit
authors: S
authors: Ghosh