Solvent-Templated Folding of Perylene Bisimide Macrocycles into Coiled Double-String Ropes with Solvent-Sensitive Optical Signatures.
Peter SpenstRyan M YoungBrian T PhelanMichel KellerJakub DostálTobias BrixnerMichael R WasielewskiFrank WürthnerPublished in: Journal of the American Chemical Society (2017)
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.
Keyphrases
- ionic liquid
- single molecule
- raman spectroscopy
- energy transfer
- molecular dynamics simulations
- solar cells
- density functional theory
- perovskite solar cells
- quantum dots
- high resolution
- molecular dynamics
- magnetic resonance imaging
- magnetic resonance
- gene expression
- genome wide
- high intensity
- blood brain barrier
- dna repair
- computed tomography
- oxidative stress
- dna methylation
- contrast enhanced
- aqueous solution