Arya Yogita, Bera Sudip Kumar, Priego José Luis, Jiménez-Aparicio Reyes, Lahiri Goutam Kumar
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
Departamento de Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, E-28040 Madrid, Spain.
Dalton Trans. 2022 Jul 12;51(27):10441-10456. doi: 10.1039/d2dt01466a.
The present work aimed to obtain discrete heavier metal complexes of unperturbed deprotonated bis-lawsone (hinge-like HL = 2,2'-bis(3-hydroxy-1,4-napthoquinone). This is primarily due to its limited examples with lighter metal ions (Co, Zn, and Ga) and the fact that our earlier approach with the osmium ion facilitated its functionalisation. Herein, we demonstrated the successful synthesis and structural characterisation of L-derived diruthenium (bpy)Ru(μ-L)Ru(bpy) 1 ( = 0), (acac)Ru(μ-L)Ru(acac)2 ( = 1) and monoruthenium (pap)Ru(L) 3 ( = 0) derivatives (bpy = 2,2'-bipyridine, acac = acetylacetonate, and pap = 2-phenylazopyridine). The crystal structures established that (i) O,O/O,O donating five-membered bis-bidentate and O,O donating seven-membered bidentate chelating modes of deprotonated L in (ΔΔ/ΛΛ) diastereomeric 1, 2 and 3, respectively. (ii) The L bridging unit in 1, 2 and 3 underwent twisting its two naphthoquinone rings with respect to the ring connecting C-C bond by 73.01°, 62.15° and 59.12°, respectively. (iii) Intermolecular π-π interactions (∼3.5 Å) between the neighbouring molecules. The paramagnetic complex 2 ( = 1) with two non-interacting Ru(III) ( = 1/2) ions exhibited weak antiferromagnetic coupling only at very low temperatures. In agreement with the magnetic results, 2 displayed typical Ru-based anisotropic EPR in CHCN (<>/Δ: 2.314/0.564) but without any forbidden signal at 120 K. The complexes exhibited multiple redox processes in CHCN in the experimental potential window of ± 2.0 V SCE. The analysis of the redox steps a combined experimental and theoretical (DFT/TD-DFT) approach revealed the involvement of L to varying extents in both the oxidative and reductive processes as a consequence of its bidirectional redox non-innocent feature. The mixing of the frontier orbitals of the metal ion and L due to their closeness in energy indeed led to the resonating electronic form in certain redox states instead of any precise electronic structural state.
本工作旨在获得未受干扰的去质子化双紫胶酮（铰链状HL = 2,2'-双(3-羟基-1,4-萘醌)）的离散重金属配合物。这主要是因为其与较轻金属离子（钴、锌和镓）形成的配合物实例有限，以及我们早期使用锇离子的方法促进了其功能化。在此，我们展示了L衍生的二钌配合物(bpy)Ru(μ-L)Ru(bpy) 1 （ = 0）、(acac)Ru(μ-L)Ru(acac)2 （ = 1）和单钌配合物(pap)Ru(L) 3 （ = 0）衍生物的成功合成与结构表征（bpy = 2,2'-联吡啶，acac = 乙酰丙酮，pap = 2-苯基偶氮吡啶）。晶体结构表明：(i) 在(ΔΔ/ΛΛ)非对映异构体1、2和3中，去质子化L分别以O,O/O,O供体五元双齿和O,O供体七元双齿螯合模式存在。(ii) 1、2和3中的L桥连单元相对于连接C-C键的环，其两个萘醌环分别扭转了73.01°、62.15°和59.12°。(iii) 相邻分子之间存在分子间π-π相互作用（~3.5 Å）。具有两个非相互作用Ru(III) （ = 1/2）离子的顺磁性配合物2仅在非常低的温度下表现出弱反铁磁耦合。与磁性结果一致，2在CHCN中显示出典型的基于Ru的各向异性EPR（<>/Δ: 2.314/0.564），但在120 K时没有任何禁戒信号。这些配合物在CHCN中，在± 2.0 V SCE的实验电位窗口内表现出多个氧化还原过程。通过结合实验和理论（DFT/TD-DFT）方法对氧化还原步骤的分析表明，由于其双向氧化还原非无辜特征，L在氧化和还原过程中均有不同程度的参与。金属离子和L的前沿轨道由于能量接近而混合，确实导致了在某些氧化还原状态下的共振电子形式，而不是任何精确的电子结构状态。
