Ensemble and Single-Molecule Spectroscopic Study on Excitation Energy Transfer Processes in 1,3-Phenylene-Linked Perylenebisimide Oligomers

Abstract

1,3-Phenylene-bridged perylenebisimide dimer (PBI2) and trimer (PBI3) were prepared along with monomer reference (PBI1) using perylene imide-anhydride 5 as a key precursor. 3,3-Dimethylbut-1-yl substituents were introduced at the 2,5-positions of perylenebisimide (PBI) to improve the solubilities of PBI oligomers. Actually, no serious aggregation of PBI2 and PBI3 was detected in their dilute CH(2)Cl(2) solutions. Under these conditions, intramolecular electronic interactions among PBI chromophores have been revealed by measuring the photophysical properties at their ensemble and single-molecule levels. The excitation energy transfer times of PBI2 (0.16 ps) and PBI3 (0.60 ps) were determined from the two different observables, anisotropy depolarization, and singlet-singlet annihilation, respectively, which are considered as the incoherent Förster-type energy hopping (EEH) times as compared with the EEH time constant (1.97 ps) calculated on the basis of the Förster mechanism. The relatively short EEH times compared to similar PBI oligomers can be attributed to 1,3-phenylene linker, which assures a short distance between the chromophores and, as a consequence, makes it hard to treat the PBI unit as a point dipole. The limitation of point-dipole approximation to describe the PBI oligomers and additional through-bond type interactions can be attributed as the causes of the discrepancies in excitation energy transfer times. Considering these photophysical properties, we can suggest that 1,3-phenylene-linked PBI oligomers have potentials as molecular photonic devices including the artificial light-harvesting system.

Folding‐Induced Modulation of Excited‐State Dynamics in an Oligophenylene–Ethynylene‐Tethered Spiral Perylene Bisimide Aggregate

“…in which τ dep is the depolarization time, which is experimentally obtained from the TAA decay profiles 29. As the two PBI units in F2 are identical, it follows that the EET time is twice that of depolarization (Table 3), thus giving rise to EET times of 1.76±0.06 ps (CHCl 3 ) and 0.95±0.06 ps (THF), respectively (Table 4).…”

Modeling Milk Heating Processes for the Production of Milk Shelf‐stable without Refrigeration

“…In addition to porphyrin, other dyes with strong absorption in the visible have been used to create dimers as, for example, derivatives of perylene (bis)imids (PBI) 21–25. H‐type PBI dimers create long‐lived excimer‐like states upon photoexcitation, the fluorescence of which is red shifted compared to the monomer 21.…”

“…22 In contrast, J‐type PBI dimers and trimers, which show a redshift in the absorption spectrum and have been investigated through single‐molecule fluorescence experiments, revealed that the lifetime of the delocalized exciton is shorter when it is shared between more monomers 23–24. If a phenyl ring was used to link the PBI derivatives, J‐type dimers and trimers were obtained with a lifetime only slightly affected by dimerization and by the presence of Förster‐type energy transfer between the constituting units 25…”

A Study of Excitation Delocalization/Localization in Multibranched Chromophores by Using Fluorescence Excitation Anisotropy Spectroscopy

“…Thus, assembly measurements, such as ultrafast time-resolved spectral measurements,a re also important to determine the delocalization of the excitation;h owever,t his methodr equires at ime resolution that is greater than 100 fs. [18][19][20][21][22] In this work, we report the fluorescence excitation and fluorescence excitation anisotropy spectra of three multibranched push-pull molecules in apolymer matrix to probe the intramolecular redistribution of the excitation energy among the multibranched chromophores. Our results directly reflect the interplay between the chromophores, and hence,a llow the excita-tion localization/delocalization in multibranched chromophores to be determined.…”