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Photophysical properties of a supramolecular interlocked conjugate

Lookup NU author(s): Professor Andrew Benniston, Emeritus Professor Anthony Harriman, Craig Sams

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Abstract

The binding behavior between a rigid, π-accepting aromatic polycycle (ADIQ·2PF6) and an electron-donating crown ether (CE(10)) is reported in acetonitrile solution. In CH3CN at low concentration of crown ether, the binding data are consistent with formation of a 1:1 complex in which the ADIQ·2PF6 residue is partially encapsulated by the crown ether (K1 ≈ 500 dm3 mol-1). As the mole fraction of crown ether increases, mass spectrometry indicates formation of a molecular aggregate in which two crown ethers are bound to a single ADIQ·2PF6 entity in the form of a pseudorotaxane. Molecular modeling and NMR spectroscopic studies indicate that the crown ether fits loosely on the end of the polycycle without significant penetration along the molecular axis. Binding causes extinction of fluorescence from the polycycle, allowing estimation of the second binding constant (K2 ≈ 400 dm3 mol-1), and results in the appearance of a charge-transfer absorption band in the visible region. Illumination into this absorption band promotes formation of an intimate radical ion pair with a time constant of ca. 3 ps. Subsequent charge recombination occurs with a lifetime of ca. 25 ps and results in greatly enhanced population of the triplet excited state localized on the polycycle. There is little or no separation of the radical ion pair into solvated ions.


Publication metadata

Author(s): Benniston AC, Davies M, Harriman A, Sams C

Publication type: Article

Publication status: Published

Journal: Journal of Physical Chemistry A

Year: 2003

Volume: 107

Issue: 23

Pages: 4669-4675

ISSN (print): 1089-5639

ISSN (electronic): 1520-5215

Publisher: American Chemical Society

URL: http://dx.doi.org/10.1021/jp034147z

DOI: 10.1021/jp034147z


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