Structure–Property Relationship of Perylene Bisimide Macrocycles Probed by Atomic Force Microscopy and Single-Molecule Fluorescence Spectroscopy

Abstract

Properties of a series of acetylene-linked perylene bisimide (PBI) macrocycles with different ring size composed of three to six PBI dyes were investigated by atomic force microscopy (AFM) and single-molecule fluorescence spectroscopy in a condensed phase. It was demonstrated that the structures of PBI cyclic arrays (CNs, N = 3, 4, 5, and 6) become distorted with increasing the ring size through molecular dynamics (MD) simulations (PM6-DH2 method) and AFM height images of CNs on highly ordered pyrolytic graphite (HOPG) surface. The MD simulations showed that only C5 and C6 rings are highly flexible molecules whose planarization goes along with a significant energetic penalty. Accordingly, both molecules did not show ordered adlayers on a HOPG surface. In contrast, C3 and C4 are far more rigid molecules leading to well-ordered hexagonal (C3) and rectangular (C4) 2D lattices. At the single-molecule level, we showed that the fluorescence properties of single CNs are affected by the structural changes. The fluorescence lifetimes of CNs became shorter and their distributions became broader due to the structural distortions with increasing the ring size. Furthermore, the CNs of smaller ring size exhibit a higher photostability and an efficient excitation energy transfer (EET) due to the more well-defined and planar structures compared to the larger CNs. Consequently, these observations provide evidence that not only PBI macrocycles are promising candidates for artificial light-harvesting systems, but also the photophysical properties of CNs are strongly related to the structural rigidity of CNs.

Phenylene Ethynylene‐Tethered Perylene Bisimide Folda‐Dimer and Folda‐Trimer: Investigations on Folding Features in Ground and Excited States

“…For comparison, an energy barrier of only 25 kJ mol À1 was calculated for a related 1,8-naphthalene imide bearing a meta-ethynyl phenylene (instead of isopropyl) imide substituent. [30] Accordingly, also DFT calculations support our conclusion that the hindered rotation around the CÀN bond with a swallowtail imide substituent, and not that of ethynyl phenylene substituent is responsible for the observed temperature-dependent 1 H NMR spectral changes in the 274-333 K temperature regime in [D 8 ]THF (also see the Section: Theoretical calculations).…”

Excited‐State Dynamic Planarization of Cyclic Oligothiophenes in the Vicinity of a Ring‐to‐Linear Excitonic Behavioral Turning Point

“…[47] This presumption is supported by the shape of the distributions resembling that of aMaxwell-Boltzmann distribution, which describes the distribution of the population over quantized energy states in thermal equilibrium. C-6 T shows surprisingly sharp distribution near 0 2 whereas C-12 T shows ab road dragging distribution to 50 2 (distribution over 30 2 is truncated as aresult of low counts).…”

Energy and Electron Transfer of One-Dimensional Nanomaterials of Perylenediimides

“…20 It is found that the excitons are migrating in one dimension (along the long axis of PDI stacks) instead of moving in all directions as in the Förster-type energy transfer, as examined in cyclic macromolecules of PDIs with various sizes. 40,41 Maximum exciton diffusion length is estimated to be 96 nm with a diffusion constant of 1.29 nm 2 /ps for a exciton lifetime of 3.6 ns in the J-aggregates of 2 in MCH. 20 Exciton delocalization was also reported within the helical π-stacks of 3 in another study.…”