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  • Perspective
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Charge-transfer processes in metal complexes enable luminescence and memory functions

Nature Reviews Chemistry volume 4, pages 528–541 (2020)Cite this article

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Abstract

Molecular transition-metal–ligand complexes are emerging as useful paradigms in materials science. Transition metal complexes have diverse metal d electron configurations, oxidation states, coordination numbers and geometries such that they can undergo a diverse array of electronic transitions. Metal-to-ligand charge-transfer transitions and their associated excited states are especially attractive given their rich redox properties and robustness. This chemistry is accessible by appropriate choice of low-valence metal centres and strong π-acceptor ligands. An in-depth fundamental understanding of their charge-transfer, assembly and structure–property relationships is important to allow us to rationally design complexes and tune their characteristics for an intended application. In addition to their attractive light-harvesting and photocatalytic applications, this Perspective describes recent developments in the use of transition metal complexes as materials in phosphorescent organic light-emitting diodes and resistive memory devices.

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Fig. 1: Donor–acceptor Ptii complexes undergo charge-transfer transitions for artificial light harvesting.
Fig. 2: Host–guest interactions enable organization of Ptii motifs into well-defined assemblies.
Fig. 3: Molecular design and structure–property control of strongly luminescent Ptii complexes for OLED fabrication.
Fig. 4: Versatile phosphorescent Auiii complexes with sophisticated optical features.
Fig. 5: Metal complexes have properties that can be exploited in resistive memory devices.
Fig. 6: Transition metal complexes afford diverse memory switching behaviour.

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Acknowledgements

V.W.-W.Y. acknowledges support from the University of Hong Kong under the University Research Committee Strategically Oriented Research Theme on Functional Materials for Molecular Electronics. This work was supported by a General Research Fund grant from the Research Grants Council of Hong Kong Special Administrative Region, People’s Republic of China (HKU 17306219). The authors acknowledge M. H.-Y. Chan and Y.-H. Cheng for their technical assistance in the preparation of the final version of the manuscript.

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  1. Institute of Molecular Functional Materials and Department of Chemistry, The University of Hong Kong, Hong Kong, People’s Republic of China

    Vivian Wing-Wah Yam, Alan Kwun-Wa Chan & Eugene Yau-Hin Hong

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All authors contributed to the writing and editing of the article. A.K.-W.C. and E.Y.-H.H. contributed equally to this work.

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Yam, V.WW., Chan, A.KW. & Hong, E.YH. Charge-transfer processes in metal complexes enable luminescence and memory functions. Nat Rev Chem 4, 528–541 (2020). https://doi.org/10.1038/s41570-020-0199-7

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