Ghosh Subrata, Bagchi Sukanya, Kamilya Sujit, Mondal Abhishake
Solid State and Structural Chemistry Unit, Indian Institute of Science, Sir C V Raman Road, Bangalore 560012, India.
Dalton Trans. 2021 Apr 7;50(13):4634-4642. doi: 10.1039/d1dt00284h. Epub 2021 Mar 15.
Three mononuclear manganese(iii) complexes based on flexible hexadentate ligands obtained from the condensation of N,N'-bis(3-aminopropyl)ethylenediamine and salicylaldehyde or salicylaldehyde with substitutions at the 5 or 3,5 positions, namely Mn(X-sal-323) (X = 5 H, 1; X = 5 Br, 2, and X = 3,5 Br, 3) have been synthesized. The impact of ligand substituents has been studied by variable temperature single-crystal X-ray diffraction analyses, and magnetic, spectroscopic and electrochemical investigations. The complexes have an analogous monocationic MnNO surrounding offered by the flexible hexadentate ligand in a distorted octahedral geometry. Complex 1 remains in the high spin state over the entire temperature range, while complex 2 shows a reversible and complete two-step thermo-induced spin-state switching. An incomplete spin-state switching from a high spin to an intermediate high-spin low-spin (1 : 1) state was observed for complex 3. Single-crystal X-ray structural studies show the presence of three different spin states in 2 during the occurrence of the spin-state switching process. Electrochemical investigations showed that the reduced state of manganese(iii) centers in 3 is easily accessible in comparison to complexes 1 and 2.
通过N,N'-双(3-氨丙基)乙二胺与水杨醛或5位或3,5位有取代基的水杨醛缩合得到的基于柔性六齿配体的三种单核锰(III)配合物，即Mn(X-sal-323)（X = 5-H，1；X = 5-Br，2；X = 3,5-Br，3）已被合成。通过变温单晶X射线衍射分析、磁性、光谱和电化学研究，研究了配体取代基的影响。这些配合物具有类似的单核阳离子MnNO环境，由柔性六齿配体以扭曲的八面体几何构型提供。配合物1在整个温度范围内保持高自旋态，而配合物2显示出可逆且完全的两步热诱导自旋态转换。对于配合物3，观察到从高自旋到中间高自旋低自旋（1∶1）态的不完全自旋态转换。单晶X射线结构研究表明，在自旋态转换过程中，配合物2中存在三种不同的自旋态。电化学研究表明，与配合物1和2相比，配合物3中锰(III)中心的还原态易于获得。
