Electrochemical probing of ground state electronic interactions in polynuclear complexes of a new heteroditopic ligand
作者:Edwin C. Constable、Egbert Figgemeier、Catherine E. Housecroft、Jerry Olsson、Yves C. Zimmermann
DOI:10.1039/b404602a
日期:——
The synthesis and electronic properties of dinuclear ([(bipy)2Ru(I)M(terpy)][PF6]4
(bipy = 2,2′-bipyridine, terpy = 2,2′:6′,2″-terpyridine; M = Ru, Os)) and trinuclear ([(bipy)2Ru(I)}2M][PF6]6 M = Ru, Os, Fe, Co) complexes bridged by 4′-(2,2′-bipyridin-4-yl)-2,2′:6′,2″-terpyridine (I) have been investigated and are compared with those of mononuclear model complexes. The electrochemical analysis using cyclic voltammetry and differential pulse voltammetry reveals that there are no interactions in the ground state between adjacent metal centres. However, there is strong electronic communication between the 2,2′-bipyridine and 2,2′:6′,2″-terpyridine components of the bridging ligand. This conclusion is supported by a step-by-step reduction of the dinuclear and trinuclear complexes and the assignment of each electrochemical process to localised ligand sites within the didentate and terdentate domains. The investigation of the electronic absorption and emission spectra reveals an energy transfer in the excited state from the terminating bipy-bound metal centres to the central terpy-bound metal centre. This indicates that the bridge is able to facilitate energy transfer in the excited state between the metal centres despite the lack of interactions in the ground state.
双核([(bipy)2Ru(I)M(terpy)][PF6]4(bipy = 2,2′-联吡啶,terpy = 2,2′:6′,2″-三吡啶;M = Ru、Os))和三核([(bipy)2Ru(I)}2M][PF6]6 M = Ru、Os、Fe、Co)配合物,由 4′-(2,2′-联吡啶-4-基)-2,2′:6′,2″-terpyridine (I) 桥接的 Co.使用循环伏安法和差分脉冲伏安法进行的电化学分析表明,相邻金属中心之间在基态没有相互作用。然而,桥接配体中的 2,2′-联吡啶和 2,2′:6′,2″-三吡啶成分之间存在着强烈的电子通信。通过逐步还原二核和三核配合物,并将每个电化学过程分配到二齿和三齿域内的局部配体位点,这一结论得到了支持。对电子吸收和发射光谱的研究表明,激发态的能量转移是从终端的双键结合金属中心转移到中心的三键结合金属中心。这表明,尽管在基态缺乏相互作用,但该桥能够促进金属中心之间在激发态的能量转移。