title: Solvent-Templated Folding of Perylene Bisimide Macrocycles into Coiled Double-String Ropes with Solvent-Sensitive Optical Signatures.
abstract: A series of semirigid perylene bisimide (PBI) macrocycles with varied ring size containing two to nine PBI chromophores were synthesized in a one-pot reaction and their photophysical properties characterized by fluorescence, steady-state, and transient absorption spectroscopy as well as femtosecond stimulated Raman spectroscopy. These macrocycles show solvent-dependent conformational equilibria and excited-state properties. In dichloromethane, the macrocycles prevail in wide-stretched conformations and upon photoexcitation exhibit symmetry-breaking charge separation followed by charge recombination to triplet states, which photosensitize singlet oxygen formation. In contrast, in aromatic solvents folding of the macrocycles with a distinct odd-even effect regarding the number of PBI chromophore units was observed in steady-state and time-resolved absorption and fluorescence spectroscopy as well as femtosecond stimulated Raman spectroscopy. These distinctive optical properties are attributable to the folding of the even-membered macrocycles into exciton-vibrational coupled dimer pairs in aromatic solvents. Studies in a variety of aromatic solvents indicate that these solvents embed between PBI dimer pairs and accordingly template the folding of even-membered PBI macrocycles into ropelike folded conformations that give rise to solvent-specific exciton-vibrational couplings in UV-vis absorption spectra. As a consequence of the embedding of solvent molecules in the coiled double-string rope architecture, highly solvent specific intensity ratios are observed for the two lowest-energy exciton-vibrational bands, enabling assignment of the respective solvent simply based on the absorption spectra measured for the tetramer macrocycle.
authors.forename: Peter
authors.initials: P
authors.lastname: Spenst
authors.affiliation: Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors.forename: Ryan M
authors.identifier: 0000-0002-5108-0261
authors.initials: RM
authors.lastname: Young
authors.affiliation: Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors.forename: Brian T
authors.identifier: 0000-0002-5849-0319
authors.initials: BT
authors.lastname: Phelan
authors.forename: Michel
authors.initials: M
authors.lastname: Keller
authors.forename: Jakub
authors.initials: J
authors.lastname: Dostál
authors.forename: Tobias
authors.identifier: 0000-0002-6529-704X
authors.initials: T
authors.lastname: Brixner
authors.affiliation: Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors.forename: Michael R
authors.identifier: 0000-0003-2920-5440
authors.initials: MR
authors.lastname: Wasielewski
authors.forename: Frank
authors.identifier: 0000-0001-7245-0471
authors.initials: F
authors.lastname: Würthner