Synthesis and Structural, Electrochemical, and Optical Properties of Ru(II) Complexes with Azobis(2,2'-bipyridine)s
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- 作者：Joe Otsuki ; Nobuyuki Omokawa ; Kenji Yoshiba ; Isao Yoshikawa ; Tetsuo Akasaka ; Tomoyoshi Suenobu ; Toshio Takido ; Koji Araki ; and Shunichi Fukuzumi
- 刊名：Inorganic Chemistry
- 出版年：2003
- 出版时间：May 5, 2003
- 年：2003
- 卷：42
- 期：9
- 页码：3057 - 3066
- 全文大小：256K
- 年卷期：v.42,no.9(May 5, 2003)
- ISSN：1520-510X
文摘
Two new ditopic ligands, 5,5' '-azobis(2,2'-bipyridine) (5,5' '-azo) and 5,5' '-azoxybis(2,2'-bipyridine) (5,5' '-azoxy),were prepared by the reduction of nitro precursors. Mononuclear and dinuclear Ru(II) complexes having one ofthese bridging ligands and 2,2'-bipyridine terminal ligands were also prepared, and their properties were comparedwith previously reported Ru(II) complexes having 4,4' '-azobis(2,2'-bipyridine) (4,4' '-azo). The X-ray crystal structureshowed that 5,5' '-azo adopts the trans conformation and a planar rodlike shape. The X-ray crystal structure of[(bpy)2Ru(5,5' '-azo)Ru(bpy)2](PF6)4 (Ru(5,5' '-azo)Ru) showed that the bridging ligand is in the trans conformationand nearly planar also in the complex and the metal-to-metal distance is 10.0 Å. The azo or azoxy ligand in thesecomplexes exhibits reduction processes at less negative potentials than the terminal bpy's due to the low-lying 
*level. The electronic absorption spectra for the complexes having 5,5' '-azo or 5,5' '-azoxy exhibit an extendedlow-energy metal-to-ligand charge-transfer absorption. The ligands, 5,5' '-azo and 5,5' '-azoxy, and the mononuclearcomplex, [(bpy)2Ru(5,5' '-azo)]2+, isomerize reversibly upon light irradiation. The low-energy MLCT state sensitizesthe isomerization of the azo moiety in this complex. While [(bpy)2Ru(4,4' '-azo)Ru(bpy)2](PF6)4 exhibits light switchproperties, namely, significant electrochromism and a large luminescence enhancement, upon reduction, Ru(5,5' '-azo)Ru does not show these properties. The radical anion formation upon reduction of these complexes has beenconfirmed by ESR spectroscopy.
*level. The electronic absorption spectra for the complexes having 5,5' '-azo or 5,5' '-azoxy exhibit an extendedlow-energy metal-to-ligand charge-transfer absorption. The ligands, 5,5' '-azo and 5,5' '-azoxy, and the mononuclearcomplex, [(bpy)2Ru(5,5' '-azo)]2+, isomerize reversibly upon light irradiation. The low-energy MLCT state sensitizesthe isomerization of the azo moiety in this complex. While [(bpy)2Ru(4,4' '-azo)Ru(bpy)2](PF6)4 exhibits light switchproperties, namely, significant electrochromism and a large luminescence enhancement, upon reduction, Ru(5,5' '-azo)Ru does not show these properties. The radical anion formation upon reduction of these complexes has beenconfirmed by ESR spectroscopy.