function is beyond the reach of many ordinary neutral ligand catalysts, which require
stronger chemical oxidants to assist catalysts in catalytic water oxidation. In 2009,
Ru(bda)(pic) 2 , a mononuclear ruthenium catalyst reported by Sun group as water
oxidation catalyst, confirmed the rationality of the analysis and showed significantly
lower redox potential [220].
Then in 2010, Sun group synthesized and characterized mononuclear ruthenium
compounds O96–97 (Fig. 40) containing double negative charge tridentate pdc
ligands [221]. The electron cloud density of Ru center was increased dramatically
by pdc ligand, which reduced the initial potential of catalytic water oxidation and
matched Ru
III/II potential of common [Ru(bpy) 3 ]
2+ photosensitizer. Although the
Fig. 39 Structures of Ru complexes O91–95
Fig. 40 Representation of the two Ru-based complexes O96 and O97, housing the negatively
charged tridentate pdc ligand
The Application of Pincer Ligand in Catalytic Water Splitting
425