Contents 1. Scope and Limitations 759 2. General Background 760 2.1. Localized Molecular Orbital Approximation 760 2.1.1. Classification of Excited States in Mononuclear Complexes 761 2.1.

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Decanuclear homoand heterometallic complexes of the general formula Mcj(BL)M;[(BL)Mp(L)2]2)320+ have been prepared as PF6" salts. The central (Mc), intermediate (Mj), and peripheral (M.) metal ions are Ru2+ or 0s2+, BL is the bridging ligand 2,3-bis(2-pyridyl)pyrazine (2,3-dpp), and L is either 2,2'-bipyridine (Spy) or 2,2'-biquinoline (biq). The decanuclear complexes have Seen synthesized by the reaction of appropriate building blocks, namely MC(BL)32+ cores, which contain three free chelating sites, with Mj[(BL)Mp(L)2]2Cl24+ species, which contain easily replaceable Cl" ligands. The six compounds prepared contain the following metals (M) and ligands (L) (BL is 2,3-dpp in all cases):

The new functionalized polypyridine ligands 4‘-(4-chlorophenyl)-6‘-phenyl-2,2‘-bipyridine (clpbpy), 4‘-(4-tolyl)-6‘-phenyl-2,2‘-bipyridine (tpbpy), and 4‘-(4-carboxyphenyl)-6‘-phenyl-2,2‘-bipyridine (cpbpy), together with the known 4‘-(4-hydroxyphenyl)-6‘-phenyl-2,2‘-bipyridine (hpbpy) and 4‘-(4-tolyl)-2,2‘:6‘,2‘ ‘-terpyridine (ttpy) have been used to prepare a new series of Ir(III) cyclometalated compounds [Ir(ppy)2(HL-X)][PF6] (ppy is the monoanion of 2-phenylpyridine; HL-X = hpbpy (1), clpbpy (2), tpbpy (3), cpbpy (4), and ttpy (5)). All the new species have been characterized by IR and 1H NMR, and the crystal structure of 4 is also presented and discussed. All the metal complexes exhibit oxidation mainly centered on an orbital derived from an Ir−(C-) σ-bond and ligand-centered reduction processes; all of them are luminescent from 3MLCT levels both at 77 K in a rigid matrix and at 298 K in fluid solution. The redox and absorption properties are more or less insensitive to the remote substituents on the rotationally free 4‘-phenyl ring, whereas fine-tuning of the luminescence properties is observed on changing substituents. The results show that the “energy gap law” for radiationless decay in the weak coupling limit is obeyed by this series of complexes, when complex 5 is excluded. Interestingly, the slope of the linear relationship between ln k nr and the emission energy at room temperature is significantly smoother than that reported for other luminescent polypyridine complexes containing different metals. Because of the high luminescence quantum yield and the presence of functionalities in the polypyridine ligand framework, the complexes reported may be considered as useful building blocks for light- and redox-active, multicomponent supramolecular systems.