Tracking the Formation of a Polynuclear Co16 Complex and Its Elimination and Substitution Reactions by Mass Spectroscopy and Crystallography
Tracking the Formation of a Polynuclear Co16 Complex and Its Elimination and Substitution Reactions by Mass Spectroscopy and Crystallography
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DOI：
10.1021/ja3123784
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发表时间：
2013-05-29
影响因子：
15
通讯作者：
Kurmoo, Mohamedally
中科院分区：
文献类型：
--
作者：
Hu, Yue-Qiao;Zeng, Ming-Hua;Kurmoo, Mohamedally
本文报道了最大的手性钴配合物[Co-16（L）（4）（H3 L）（8）-（N-3）（6）]（NO3）（2）中心点16 H（2）O中心点2CH（3）OH（1，其中H4 L = S，S-1，2-bis-（1H-benzimidazol-2-yl）-1，2-ethanol）的合成和结构。1由两个Co 4 O 4立方体（Co-4（L）（2）（H3 L）（2））与Co-2（EO-N-3）（2）Co-2（Co-4（L）（2）（H3 L）（2）（2））交替组成，通过苯并咪唑和叠氮氮原子桥接形成扭环。配体具有顺式和反式两种构型，且所有环具有相同的手性。来自晶体的甲醇溶液的1的ESI-MS显示片段[Co-16（L）（4）（H3 L）（8）（N-3）（6）+2H]（4+），表明多核在溶液中是稳定的。从反应溶液的ESI-MS测量发现较小的碎片，[Co-4（H3 L）（4）-H]（3+）、[Co-4（H3 L）（4）-2H]（2+）、[Co-4（H3 L）（4）（N-3）（2）]（2+）和[Co-2（H3 L）（2）]（2+），并且从固体存款的甲醇溶液的ESI-MS发现另外的Co-16核。这些结果和对合成时间的依赖性使我们能够提出1的形成过程，这为直接观察配体控制的团簇组装开辟了一条新的途径。[Co-4（H3 L）（4）]（NO3）（4）中心点4 H（2）O（2）的分离支持了该提议，该中心点由单独的Co 4 O 4立方体组成，配体仅为晶体形式的顺式。有趣的是，N-3（-）被取代的CH-3 O-或OH-，这是第一次，高分辨率ESI-MS被成功地用于检查两个逐步消除和取代的内部桥接配体在这样的高核配合物。增加电压导致叠氮化物从母体簇中逐步消除。初步磁化率为1表明铁磁立方体反铁磁耦合到尘埃内的正方形，但在2.5 kOe的磁场中，在4 K以下观察到微弱而缓慢的弛豫。
We present the syntheses and structures of the biggest chiral cobalt coordination cluster, [Co-16(L)(4)(H3L)(8)-(N-3)(6)](NO3)(2)center dot 16H(2)O center dot 2CH(3)OH (1, where H4L = S,S-1,2-bis-(1H-benzimidazol-2-yl)-1,2-ethanediol). 1 consists of two Co4O4 cubes (Co-4(L)(2)(H3L)(2)) alternating with Co-2(EO-N-3)(2)Co-2 (Co-4(L)(2)(H3L)(2)(N-3)(2)), bridged by the benzimidazole and azide nitrogen atoms to form a twisted ring. The ligand adopts both cis and trans forms, and all the rings have the same chiralilty. ESI-MS of 1 from a methanol solution of crystals reveals the fragment [Co-16(L)(4)(H3L)(8)(N-3)(6)+2H](4+), suggesting the polynuclear core is stable in solution. ESI-MS measurements from the reaction solution found smaller fragments, [Co-4(H3L)(4)-H](3+), [Co-4(H3L)(4)-2H](2+), [Co-4(H3L)(4)(N-3)(2)](2+), and [Co-2(H3L)(2)](2+), and ESI-MS from a methanol solution of the solid deposit found in addition the Co-16 core. These results and the dependence on the synthesis time allow us to propose the process for the formation of 1, which opens up a new way for the direct observation of the ligand-controlled assembly of clusters In addition, the isolation of [Co-4(H3L)(4)](NO3)(4)center dot 4H(2)O (2) consisting of separate Co4O4 cubes with the ligands being only cis in crystalline form supports the proposal. Interestingly, N-3(-) is replaced by either CH3O- or OH-, and this is the first time that high resolution ESI-MS is successfully utilized to examine both the step-by-step elimination and substitution of inner bridging ligands in such a high nuclear complex. Increasing the voltage results in stepwise elimination of azide from the parent cluster. The preliminary magnetic susceptibility of 1 indicates ferromagnetic cubes antiferromagnetically coupled to the squares within the duster, though in a field of 2.5 kOe, weak and slow relaxation is observed below 4 K.