Polypyridyl ligands metal complexes

Numerous metal complexes have been proven to be active electrocatalysts for C02 reduction.1,66-68 These catalysts can be conveniently grouped into three main families metal complexes with polypyridyl ligands, metal complexes with macrocyclic ligands, and metal complexes with phosphorus ligands. 

Polypyridyl ligand-bridged complexes in which coupling appears to be promoted by ligand-to-metal charge transfer (hole transfer systems)... 

Polypyridyl ligands are able to stabilize electron-rich metal centers as has been shown for the d -systems Ru and Os. This suggests this class of ligands also to be appropriate for rhenium(I) compounds, and this will be discussed more in detail in Section 5.3.2.7.2, and rhenium(II) complexes which represent intermediates in the syntheses of the Re species or are accessed by oxidation of Re. ... 

The ability of polypyridyl ligands to accept electron density from electron-rich rhenium centers and, thus, to contribute to the stabilization of rhenium complexes with the metal in low oxidation states has already been discussed for rhenium(II) compounds. Only small modifications to the polypyridyl ligand or the metal center can create dramatic differences in the properties of the resulting complexes. Generally, the starting materials which have been introduced as precursors for rhenium(II) polypyridyl complexes in Section 5.3.2.6.2, are also appropriate for the synthesis of related rhenium(l) compounds. 

Balzani et al. (70) employed a strategy focusing on complexes as metals and as ligands (71,72), for developing a number of interesting supramolecular systems. Ditopic polypyridyl ligands, for example, 2,3- and 2,5-dipyridylpyrazine (2,3-dpp and 2,5-dpp), 2,2 -biquinoline (biq), tetrapyrido[3,2-fl 2, 3 -c 3",2"-/z 2", 3 "-/]-phenazine (73,74) (tppz), and 2,3,5,6-tetrakis(2-pyridyl)pyrazine (75-77) (tpypz), in combination with monotopic ligands (e.g., bpy and phen) were utilized in the preparation of a number of homo- and heteropolynuclear complexes of well-defined structures (Fig. 2). 

METAL-POLYPYRIDINE COMPLEXES. The majority of the mechanistic data has come from studies on complexes containing polypyridyl ligands. Among the appealing properties of ligands like 2, 2 -bipyridine (bpy) and 1,... 

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