Controlling the redox properties of a pyrroloquinolinequinone (PQQ) derivative in a ruthenium(II) coordination sphere
Controlling the redox properties of a pyrroloquinolinequinone (PQQ) derivative in a ruthenium(II) coordination sphere
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DOI：
10.1039/c4dt03358b
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发表时间：
2015-01-01
影响因子：
4
通讯作者：
Kojima, Takahiko
中科院分区：
文献类型：
--
作者：
Mitome, Hiroumi;Ishizuka, Tomoya;Kojima, Takahiko
以三齿配体2，2‘：6’，2‘’-三联吡啶(TERPY)为辅基，合成了氧化还原活性PQQ的三甲酯衍生物PQQTME的Ru(II)配合物。通过光谱分析、X-射线结晶学和电化学测试等手段对配合物进行了表征。在一个络合物中，PQTME的吡啶中心以三齿配体的形式与[RuII(Terpy)]单元结合，而银(I)离子以双齿方式与苯二酚部分配位。相反，另一个络合物在PQTME配体的双齿对苯二酚部分包括[Ru-II(Terpy)]单元。络合物配位方式的不同在金属配位的稳定性和PQTME配体还原过程的可逆性方面也表现出特征的差异。应该注意的是，额外的金属离子与PQQTME配体的结合大大提高了配体的1e(-)-还原电位。此外，我们还成功地用UV-Vis吸收光谱和ESR光谱表征了配合物的1e(-)还原物种，其中未成对的电子在PQQTME(中心点-)配体的pi共轭体系中离域。
Ruthenium(II) complexes of PQQTME, a trimethyl ester derivative of redox-active PQQ (pyrroloquinolinequinone), were prepared using a tridentate ligand, 2,2': 6', 2 ''-terpyridine (terpy) as an auxiliary ligand. The characterization of the complexes was performed by spectroscopic methods, X-ray crystallography, and electrochemical measurements. In one complex, the pyridine site of PQQTME binds to the [RuII(terpy)] unit as a tridentate ligand, and a silver(I) ion is coordinated by the quinone moiety in a bidentate fashion. In contrast, another complex includes the [Ru-II(terpy)] unit at the bidentate quinone moiety of the PQQTME ligand. The difference in the coordination modes of the complexes exhibits a characteristic difference in the stability of metal coordination and also in the reversibility of the reduction processes of the PQQTME ligand. It should be noted that an additional metal-ion-binding to the PQQTME ligand largely raises the 1e(-)-reduction potential of the ligand. In addition, we succeeded in the characterization of the 1e(-)-reduced species of the complexes, where the unpaired electron was delocalized in the pi-conjugated system of the PQQTME(center dot-) ligand, using UV-Vis absorption and ESR spectroscopies.