Issue 23, 2010
From the journal:

Organic & Biomolecular Chemistry

Electronic structural dependence of the photophysical properties of fluorescent heteroditopic ligands – implications in designing molecular fluorescent indicators†

Ali H. Younes,a   Lu Zhang,a   Ronald J. Clark,a   Michael W. Davidson*b  and  Lei Zhu*a  

* Corresponding authors

a Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306-4390, USA
E-mail: lzhu@chem.fsu.edu
Fax: +1 850 644 8281
Tel: +1 850 645 6813

b National High Magnetic Field Laboratory and Department of Biological Science, Florida State University, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, USA
E-mail: davidson@magnet.fsu.edu.
Fax: +1 850 644 8920
Tel: +1 850 644 0542

Abstract

Two fluorescent heteroditopic ligands (2a and 2b) for zinc ion were synthesized and studied. The efficiencies of two photophysical processes, intramolecular charge transfer (ICT) and photoinduced electron transfer (PET), determine the magnitudes of emission bathochromic shift and enhancement, respectively, when a heteroditopic ligand forms mono- or dizinc complexes. The electron-rich 2b is characterized by a high degree of ICT in the excited state with little propensity for PET, which is manifested in a large bathochromic shift of emission upon Zn2+ coordination without enhancement in fluorescence quantum yield. The electron-poor 2a displays the opposite photophysical consequence where Zn2+ binding results in greatly enhanced emission without significant spectral shift. The electronic structural effects on the relative efficiencies of ICT and PET in 2a and 2b as well as the impact of Zn2+-coordination are probed using experimental and computational approaches. This study reveals that the delicate balance between various photophysical pathways (e.g. ICT and PET) engineered in a heteroditopic ligand is sensitively dependent on the electronic structure of the ligand, i.e. whether the fluorophore is electron-rich or poor, whether it possesses a donor–acceptor type of structure, and where the metal binding occurs.

Graphical abstract: Electronic structural dependence of the photophysical properties of fluorescent heteroditopic ligands – implications in designing molecular fluorescent indicators

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Article information

DOI
https://doi.org/10.1039/C0OB00482K
Article type
Paper
Submitted
23 Jul 2010
Accepted
03 Sep 2010
First published
06 Sep 2010

Org. Biomol. Chem., 2010,8, 5431-5441

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Electronic structural dependence of the photophysical properties of fluorescent heteroditopic ligands – implications in designing molecular fluorescent indicators

A. H. Younes, L. Zhang, R. J. Clark, M. W. Davidson and L. Zhu, Org. Biomol. Chem., 2010, 8, 5431 DOI: 10.1039/C0OB00482K

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