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Divergent Approach for Tris-Heteroleptic Cyclometalated Iridium Complexes Using Triisopropylsilylethynyl-Substituted Synthons

Edkins, Robert M.; Hsu, Yu-Ting; Fox, Mark A.; Yufit, Dmitry; Beeby, Andrew; Davidson, Ross J.

Divergent Approach for Tris-Heteroleptic Cyclometalated Iridium Complexes Using Triisopropylsilylethynyl-Substituted Synthons Thumbnail


Authors

Robert M. Edkins

Yu-Ting Hsu



Abstract

Bis-heteroleptic cyclometalated iridium complexes of the form Ir(La)2(acac), where La is a substituted 2-phenylpyridine derivative and acac is an acetylacetonato ligand, are a useful class of luminescent organometallic complexes for a range of applications. Related tris-heteroleptic complexes of the form Ir(La)(Lb)(acac) offer the potential advantage of greater functionality through the use of two different cyclometalated ligands but are, in general, more difficult to obtain. We report the synthesis of divergent bis- and tris-heteroleptic triisopropylsilylethynyl-substituted intermediate complexes that can be diversified using a “chemistry-on-the-complex” approach. We demonstrate the methodology through one-pot deprotection and Sonogashira cross-coupling of the intermediate complexes with para-R-aryliodides (R = H, SMe, and CN). The photophysical and electrochemical behaviors of the resultant bis- and tris-heteroleptic complexes are compared, and it is shown that the tris-heteroleptic complexes exhibit subtly different emission and redox properties to the bis-heteroleptic complexes, such as further red-shifted emission maxima and lower extinction coefficients, which can be attributed to the reduced symmetry. It is demonstrated, supported by DFT and time-dependent DFT calculations, that the charge-transfer character of the emission can be altered via variation of the terminal substituent; the introduction of an electron-withdrawing cyano group in the terminal position leads to a significant red shift, while the introduction of an SMe group can substantially increase the emission quantum yield. Most notably, this convenient synthetic approach reduces the need to perform the often challenging isolation of tris-heteroleptic complexes to a single divergent intermediate, which will simplify access to families of complexes of the form Ir(La)(Lb)(acac).

Citation

Edkins, R. M., Hsu, Y., Fox, M. A., Yufit, D., Beeby, A., & Davidson, R. J. (2022). Divergent Approach for Tris-Heteroleptic Cyclometalated Iridium Complexes Using Triisopropylsilylethynyl-Substituted Synthons. Organometallics, https://doi.org/10.1021/acs.organomet.2c00292

Journal Article Type Article
Acceptance Date Aug 9, 2022
Online Publication Date Aug 19, 2022
Publication Date 2022
Deposit Date Sep 2, 2022
Publicly Available Date Sep 5, 2022
Journal Organometallics
Print ISSN 0276-7333
Electronic ISSN 1520-6041
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
DOI https://doi.org/10.1021/acs.organomet.2c00292

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