1450 - 1530 Chi-Ming Che
Functional Molecular Materials and Photo-Catalysis with Phosphorescent Square Planar Metal Complexes
Square planar metal complexes with d8 electronic configuration are distinctly different from octahedral d6 metal complexes in that their structures are anisotropic with vacant coordination sites at the central metal ion, which allows for intermolecular metal-metal interactions.1-2We have recently demonstrated that d8 metal···metal interactions is a driving force for the anisotropic growth of functional molecular nanostructures including 1-D nanowires,3 semiconducting nanostructured materials for light-emitting organic thin-film field effect transistors,4 photo-responsive2-Dnano-sheets, and supramolecular polyelectrolytes.5 Square planar metal complexes can also be viewed as lipophilic ?-conjugated planar metal-organic cations/molecules depending on the choice of auxiliary ligands. Thus, they are potential metallo-intercalators for DNAs including secondary DNAs with specific binding properties. Indeed, we have demonstrated that phosphorescent platinum(II) and gold(III) complexes are effective for treatment of cancers based on extensive in vitro and in vivo animal studies. The anti-cancer mechanism has been identified to involve non-covalent binding of the metal complexes to cancer specific DNAs and/or enzyme inhibition.6 Because of vacant coordination sites at the metal ion, square planar metal complexes are candidates for developing catalysts for inner-sphere atom transfer reactions, whereby metal-substrate binding interaction is a key step for substrate activation.1,2 Among the square planar complexes, phosphorescent platinum(II) and gold(III) complexes are receiving a huge surge of interests. In this lecture, the design and application studies of phosphorescent metal complexes with long-lived electronic excited states in solutions are discussed. The four coordinated d8metal complexes with long-lived triplet excited states allow for light-induced activation of dioxygen and C-H bonds, leading to photo-catalysis for hydrogen production, aerobic organic oxidations and H-atom abstraction from hydrocarbons. The applications of phosphorescent platinum(II) complexes as components of functional nano-structured materials with novel semi-conducting, electroluminescent and photoluminescent properties which are responsive to external stimuli are presented.
References
1. Roundhill, D. M.; Gray, H. B.; Che, C.-M. Acc. Chem. Res. 1989, 22, 55.
2. Lai, S.-W.; Che, C.-M. Top. Curr. Chem. 2004, 241, 27.
3. Lu, W.; Roy, V. A. L.; Che, C.-M. Chem. Commun. 2006, 3972.
4. Yuen, M.-Y.; Roy, V. A. L.; Lu, W.; Kui, S. C.-F.; Tong, G. S. M.; So, M.-H.; Chui, S. S.-Y.; Muccini, M.; Ning, J. Q.; Xu, S. J.; Che, C.-M. Angew. Chem. Int. Ed.2008, 47, 9895.
5. Lu, W.; Chen, Y.; Roy, V. A. L.; Chui, S. S.-Y.; Che, C.-M. Angew. Chem. Int. Ed.2009, 48, 7621.
6. Che, C.-M.; Siu, F.-M. Curr. Opin. Chem. Biol. 2010, DOI 10.1016/j.cbpa.2009.11.015.
We are grateful for the financial support by The University of Hong Kong, National Natural Science Foundation of China/Research Grants Council Joint Research Scheme, The Chinese Academy of Sciences-Croucher Foundation Funding Scheme For Joint Laboratories, Research Grants Council of Hong Kong, and Areas of Excellence Scheme University Grants Committee (Hong Kong).
