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Published on: August 19, 2021
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Photoswitchable azobenzene-appended iridium(iii) complexes.
J Pérez-Miqueo1, A Altube, E García-Lecina
1Department of Applied Chemistry, Faculty of Chemistry, University of the Basque Country (UPV-EHU), 20080 San Sebastián, Spain. Zoraida_freixa@ehu.eus.
Dalton Transactions (Cambridge, England : 2003)
|July 28, 2016
Summary
Iridium complexes with extended conjugation show inhibited photochromism. Introducing a spacer restores photochromic behavior in these azobenzene-appended organometallic complexes.
Area of Science:
- Organometallic Chemistry
- Photochemistry
- Materials Science
Background:
- Azobenzene derivatives are known for their photochromic properties, undergoing reversible trans-to-cis isomerization upon light exposure.
- Iridium(III) complexes are widely studied for their photophysical properties and potential applications in lighting and sensing.
- Cyclometalated iridium(III) complexes offer a versatile platform for tuning electronic and photophysical characteristics.
Purpose of the Study:
- To investigate the influence of extended electronic conjugation and substitution patterns on the photochromic behavior of azobenzene-appended 2-phenylpyridyl (ppy) ligands.
- To synthesize and characterize novel iridium(III) complexes incorporating multiple azobenzene units.
- To establish structure-property relationships governing photochromism in these organometallic systems.
Main Methods:
- Synthesis of four novel azobenzene-containing 2-phenylpyridyl (ppy) ligands.
- Preparation of nine iridium(III) cyclometalated complexes with varying numbers of appended azobenzenes.
- Photochemical characterization using UV-vis spectroscopy to monitor trans-to-cis isomerization.
- Structural analysis using 1H-NMR spectroscopy to probe electronic communication.
Main Results:
- Extended electronic conjugation along the ligand backbone significantly inhibited the light-induced trans-to-cis isomerization of the azobenzene moiety upon coordination to iridium(III).
- The presence of an aliphatic spacer (e.g., -CH2- or -OCH2-) between the azobenzene and the ppy fragment successfully disrupted electronic communication.
- This disruption via a spacer unit enabled the recovery of photochromic behavior in the synthesized organometallic complexes.
Conclusions:
- Electronic communication through extended conjugation is detrimental to the photochromic response of azobenzene units in iridium(III) complexes.
- Strategic incorporation of aliphatic spacers is an effective strategy to decouple the azobenzene photochromism from the iridium center.
- This work provides insights into the design of photochromic organometallic materials with tunable properties.
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