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Optical spectroscopic properties recorded for simple BOPHY dyes in condensed media: The mirror-symmetry factor

Lookup NU author(s): Owen Woodford, Dr Raymond Ziessel, Emeritus Professor Anthony Harriman, Dr Corinne Wills, Abdu Alsimaree, Dr Julian Knight

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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).


Abstract

© 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.


Publication metadata

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

Data Source Location: https://doi.org/10.1016/j.saa.2018.09.047


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