Synthesis, 1H/13C NMR spectroscopic and structural studies of sterically induced internal dynamics in novel mono- and di-ruthenium(II) 2,2′∶6′,2″-terpyridine complexes of 2,3-bis(2,2′-bipyridin-6-yl)pyrazine
作者:Fenton R. Heirtzler、Markus Neuburger、Margareta Zehnder、Steven J. Bird、Keith G. Orrell、Vladimir Sik
DOI:10.1039/a807970f
日期:——
The mono- and di-metallic N6-ruthenium(II) complexes [Ru(terpy)L][PF6]2 1 and [Ru(terpy)}2L][PF6]4 2, where L is 2,3-bis(2,2â²-bipyridin-6-yl)pyrazine and terpy is 2,2â²â¶6â²,2â³-terpyridine, have been prepared. Extensive and careful 1H and 13C NMR spectroscopic studies at ambient temperature showed that complexation induces steric strain in the scaffolding of L and thereby fluxional behaviour in both complexes. In 1, rotation of the free 2,2â²-bipyridyl (bpy) group of L relieves these interactions and results in two enantiomerically related conformations. In 2, a mutual twisting of both complexed bpy fragments results in helicene-like, P- and M-configured enantiomeric complexes. Dynamic low-temperature NMR studies of 1 and 2 in acetone-d6 solutions have provided activation energy data for both processes. The behaviour of 2 is paralleled by its crystal structure, which indicated a strong twisting of the bpy groups of L. Cyclic voltammetric and UV-spectroscopic studies conducted on both indicated a mild electrochemical and electronic coupling of the metal centres in 2.
我们制备了单金属和双金属 N6-钌(II)配合物 [Ru(terpy)L][PF6]2 1 和 [Ru(terpy)}2L][PF6]4 2,其中 L 是 2,3-双(2,2â²-联吡啶-6-基)吡嗪,terpy 是 2,2â²â¶6â²,2â³-三吡啶。在常温下进行的大量细致的 1H 和 13C NMR 光谱研究表明,络合作用会导致 L 的支架产生立体应变,从而使两种络合物产生通性。在 1 号复合物中,L 的自由 2,2â²-联吡啶(bpy)基旋转缓解了这些相互作用,并产生了两种对映体相关的构象。在 2 中,两个络合的 bpy 片段相互扭转,形成螺旋状、P- 和 M-构象的对映体络合物。在丙酮-d6 溶液中对 1 和 2 进行的动态低温核磁共振研究提供了这两个过程的活化能数据。对 2 和 1 进行的循环伏安法和紫外光谱研究表明,2 中的金属中心具有温和的电化学和电子耦合作用。