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Lookup NU author(s): Dr Owen Woodford, Dr Raymond Ziessel, Emeritus Professor Anthony Harriman, Dr Corinne Wills, Abdu Alsimaree, Dr Julian Knight
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).
© 2018 Elsevier B.V. The BOPHY structural scaffold provides opportunities for the synthesis of innumerable derivatives with linear geometries and well-controlled π-conjugation pathways. The simpler BOPHY chromophores are highly fluorescent but exhibit poor mirror symmetry between absorption and fluorescence spectra at ambient temperature. In particular, the absorption (and excitation) spectra are broad and appear as two overlapping bands of comparable intensity. In constrained media, such as low-temperature rigid glasses or stretched poly(ethylene) films, mirror symmetry is restored. Analysis of the temperature dependence recorded for simple BOPHY derivatives indicates that the vibronic envelope accompanying the electronic transitions can be well described in terms of low- and medium-frequency modes. Whereas the fluorescence spectral profile is only weakly dependent on temperature, the excitation spectrum is far more affected. The magnitude of the low-frequency mode, and the associated electron-phonon coupling, increase substantially with increasing temperature and is responsible for temperature broadening and distortion of the excitation spectrum in solution. This critical low-frequency vibronic mode is associated with out-of-plane torsional bending of the BOPHY unit. Variable temperature NMR studies failed to provide unequivocal evidence for conformational changes of one of the derivatives over the temperature range 193–353 K.
Author(s): Woodford OJ, Ziessel R, Harriman A, Wills C, Alsimaree AA, Knight JG
Publication type: Article
Publication status: Published
Journal: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
Year: 2019
Volume: 208
Pages: 57-64
Print publication date: 05/02/2019
Online publication date: 28/09/2018
Acceptance date: 26/09/2018
Date deposited: 04/12/2018
ISSN (print): 1386-1425
ISSN (electronic): 1873-3557
Publisher: Elsevier BV
URL: https://doi.org/10.1016/j.saa.2018.09.047
DOI: 10.1016/j.saa.2018.09.047
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