Sundaresan Sriram, Müller Julia, Carrella Luca M, Rentschler Eva
Department Chemie, Johannes-Gutenberg-Universität Mainz Duesbergweg 10-14 55128 Mainz Germany
RSC Adv. 2025 Jun 6;15(24):19287-19294. doi: 10.1039/d5ra01958c. eCollection 2025 Jun 4.
We describe the synthesis of three cobalt complexes, C1-C3, featuring redox-active catechol ligands and a tetradentate salen ligand (L). Structural characterization using single-crystal X-ray diffraction at 120 K, along with UV-vis, infrared spectroscopy, and SQUID magnetometry, provided detailed insights into their electronic and geometric properties. Magnetic measurements revealed that the two tetrahalogenated catechol complexes (C1 and C2) remain diamagnetic up to 400 K, whereas the complex with 3,5-ditert butyl catechol (C3) shows radical characteristics and stays in semiquinone form strongly coupled with a Co(iii) centre. This radical behaviour was further confirmed by EPR spectroscopy in MeCN solution at room temperature. Cyclic voltammetry studies demonstrated the influence of catechol substituents on the electronic properties of these complexes, as reflected in shifts in oxidation potential. Preliminary investigations into their electrocatalytic activity for hydrogen production indicate that none of the complexes function effectively as catalysts under the tested conditions.
我们描述了三种钴配合物C1 - C3的合成，其具有氧化还原活性的儿茶酚配体和四齿salen配体（L）。在120 K下使用单晶X射线衍射进行结构表征，以及紫外可见光谱、红外光谱和超导量子干涉仪磁力测量，为其电子和几何性质提供了详细的见解。磁性测量表明，两种四卤代儿茶酚配合物（C1和C2）在高达400 K时仍为抗磁性，而含有3,5 -二叔丁基儿茶酚的配合物（C3）表现出自由基特征，并以半醌形式与Co(III)中心强烈耦合。这种自由基行为在室温下的MeCN溶液中通过电子顺磁共振光谱进一步得到证实。循环伏安法研究表明儿茶酚取代基对这些配合物电子性质的影响，这反映在氧化电位的变化上。对它们产氢的电催化活性的初步研究表明，在测试条件下，没有一种配合物能有效地作为催化剂起作用。
