We herein report the synthesis and magnetic properties of a Ni(II)-porphyrin tethered to an imidazole ligand through a flexible electron-responsive mechanical hinge. The latter is capable of undergoing a large amplitude and fully reversible folding motion under the effect of electrical stimulation. This redox-triggered movement is exploited to force the axial coordination of the appended imidazole ligand onto the square-planar Ni(II) center, resulting in a change in its spin state from low spin (S = 0) to high spin (S = 1) proceeding with an 80% switching efficiency. The driving force of this reversible folding motion is the π-dimerization between two electrogenerated viologen cation radicals. The folding motion and the associated spin state switching are demonstrated on the grounds of NMR, (spectro)electrochemical, and magnetic data supported by quantum calculations.

中文翻译：

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电刺激触发的镍中心配位诱导自旋态切换

我们在此报告了通过柔性电子响应机械铰链与咪唑配体连接的 Ni(II)-卟啉的合成和磁性。后者能够在电刺激的作用下进行大幅度的、完全可逆的折叠运动。这种氧化还原触发的运动被利用来迫使附加的咪唑配体轴向配位到方平面 Ni(II) 中心，导致其自旋状态从低自旋 ( S = 0) 变为高自旋 ( S= 1) 以 80% 的开关效率进行。这种可逆折叠运动的驱动力是两个电生成的紫罗碱阳离子自由基之间的 π-二聚化。折叠运动和相关的自旋状态切换是基于 NMR、（光谱）电化学和由量子计算支持的磁数据证明的。