**5. Acknowledgment**

The endeavors of past and present co-workers from my research group in obtaining the results presented in this chapter are gratefully acknowledged, their names appear in the reference list. The Institute for Molecular Science, Bruker AXS Japan and Rigaku Corporation are gratefully acknowledged for performing X-ray measurements of some complexes. Finally, I thank Mr. Takashi Yamanaka for his contribution in writing this chapter.

Role of X-Ray Crystallography in Structural Studies of Pyridyl-Ruthenium Complexes 235

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**10** 

*Japan* 

**Ruthenium(II)-Pyridylamine Complexes Having** 

Functionalization of metal complexes by introduction of functional groups has been recognized to be important toward the development of further functionality of metal

Convergence of functional groups into certain direction and appropriate spatial arrangement can be achieved by coordination of metal ions to ligands with those groups to perform novel functions that cannot be achieved by organic ligand molecules for themselves. This strategy allows us to access multifunctional molecules more easily than

Ruthenium complexes bearing chelating pyridylamine ligands are robust enough to hold those ligands in the coordination spheres for the convergence of functional groups attached to the ligands and to maintain their appropriate spatial geometry. We have used tris(2 pyridylmethyl)amine (TPA) and its derivatives which coordinate to the ruthenium ion as tetradentate ligands. Introduction of functional groups to the 6-position of pyridine rings of TPA can provide additional functionality for ruthenium-TPA complexes (Figure 1). The concept, i.e., the introduction of amide groups at the 6-positions of pyridine rings in TPA, has been originally introduced by Masuda and coworkers to construct a hydrophobic and sterically protected environment in copper complexes by using pivaloylamide groups (Harata *et al*., 1994, 1995, 1998; Wada *et al.*, 1998). They have succeeded in a number of important metal complexes in bioinorganic chemistry. Inspired by their works, we have developed our concept to functionalize ruthenium-TPA complexes by introducing various functional groups via amide linkages. In our case, the ruthenium complexes bearing trisubstituted TPA is not suitable for functionalization due to its large steric crowding. Therefore we have applied bisamide and monoamide-TPA as ligands. In this chapter, we will present an overview of a chemistry of ruthenium complexes bearing bisamide-TPA and

**2. Convergence of hydrophobic functional groups in the coordination sphere** 

According to the strategy mentioned above, we introduced hydrophobic groups to TPA toward molecular recognition based on van der Waals interactions in the coordination

complexes, including ion sensing, molecular recognition, and selective catalysis.

that with well-designed organic molecules in terms of synthetic availability.

monoamide-TPA as ligands and their characteristics.

**of ruthenium complexes** 

**1. Introduction** 

**Functional Groups via Amide Linkages** 

Soushi Miyazaki1 and Takahiko Kojima2

*2Department of Chemistry, University of Tsukuba* 

*1Research Center for Materials Science, Nagoya University* 

