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Published March 22, 2017 | Supplemental Material + Published
Journal Article Open

Intramolecular Energy and Electron Transfer Within a Diazaperopyrenium-Based Cyclophane


Molecules capable of performing highly efficient energy transfer and ultrafast photo-induced electron transfer in well-defined multichromophoric structures are indispensable to the development of artificial photosynthetic systems. Herein, we report on the synthesis, characterization and photophysical properties of a rationally designed multichromophoric tetracationic cyclophane, DAPPBox^(4+), containing a diazaperopyrenium (DAPP^(2+)) unit and an extended viologen (ExBIPY^(2+)) unit, which are linked together by two p-xylylene bridges. Both ^1H NMR spectroscopy and single crystal X-ray diffraction analysis confirm the formation of an asymmetric, rigid, box-like cyclophane, DAPPBox^(4+). The solid-state superstructure of this cyclophane reveals a herringbone-type packing motif, leading to two types of π···π interactions: (i) between the ExBIPY^(2+) unit and the DAPP^(2+) unit (π···π distance of 3.7 Å) in the adjacent parallel cyclophane, as well as (ii) between the ExBIPY^(2+) unit (π···π distance of 3.2 Å) and phenylene ring in the closest orthogonal cyclophane. Moreover, the solution-phase photophysical properties of this cyclophane have been investigated by both steady-state and time-resolved absorption and emission spectroscopies. Upon photoexcitation of DAPPBox^(4+) at 330 nm, rapid and quantitative intramolecular energy transfer occurs from the ^1*ExBIPY^(2+) unit to the DAPP^(2+) unit in 0.5 ps to yield ^1*DAPP^(2+). The same excitation wavelength simultaneously populates a higher excited state of ^1*DAPP^(2+) which then undergoes ultrafast intramolecular electron transfer from ^1*DAPP^(2+) to ExBIPY^(2+) to yield the DAPP^(3+•) – ExBIPY^(+•) radical ion pair in τ = 1.5 ps. Selective excitation of DAPP^(2+) at 505 nm populates a lower excited state where electron transfer is kinetically unfavorable.

Additional Information

© 2017 American Chemical Society. ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. Received: December 31, 2016; Published: February 22, 2017. This research was conducted as part of the Joint Center of Excellence in Integrated Nanosystems at King Abdulaziz City for Science and Technology (KACST) and Northwestern University (NU). The authors thank both KACST and NU for their continued support of this research. This work was also supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, U.S. Department of Energy (DOE) under grant no. DE-FG02-99ER14999 (M.R.W.). J.T.H. and O.K.F. gratefully acknowledge financial support by the U.S. DOE, Office of Science, Office of Basic Energy Sciences (grant No. DE-FG02 87ER13808) and Northwestern University. H.X. and W.A.G. were supported by NSF (EFRI-00155EI-1332411). The authors declare no competing financial interest.

Attached Files

Published - jacs.6b13223

Supplemental Material - ja6b13223_si_001.pdf

Supplemental Material - ja6b13223_si_002.cif


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