湖北大学曾明华团队近日揭示了原位配体转化促进分级Co₁₉配位簇的串联组装-拆卸-重组。2025年7月4日出版的《结构化学》杂志发表了这项成果。

奇数和高核配位体极为罕见，但它们代表了一个有趣的子类，缺乏规则的重复构建块和高度的结构对称性，无法理解自组装的多原子系统。

研究组通过原位配体从H₂L₁转化为L′，得到了最大的具有奇核特征的钴多齿配体基聚合物，即[Co₁₉(HL₁)₈(L₁)₁₂（L′）₂（Ac)₄]·10CH₃CH₂OH·6H₂O （1, H₂L₁= 1h -苯并[d]咪唑-2-基）甲醇，HL′= 1h -苯并[d]咪唑）。它具有分层三层和空笼式内部结构，由中央圆盘形[Co₇L₁₀]芯和两侧两个[Co₆]环组成。晶体1的ESI-MS得到一系列超过16个片段，所有片段都具有一个集成的[Co₁₉]核心，表明多核热计在溶液中的稳定性。

在从0到100 eV的持续能量增加期间，所有的MS峰都移到了较低的m/z范围内，但[Co₁₉]核心保持完整，除了逐步消除多达3个Ac阴离子或3个L1连接体。反应沉积物的PXRD跟踪显示，在3 h时形成了[Co₄L₄]立方烷的关键前驱体，在6 h时含量下降，在12 h时消失，随后在18 h时生成清晰的溶液，出现晶体1，表明了初始的clthemter组装-拆卸过程。

反应沉积物和溶液的ESI-MS谱分析进一步确定了[Co₇L₁₀]圆盘及其膨胀[Co₁₃L₁₂（L’）₂]的其他关键高核重组碎片的存在。提出了一种可能的串联组装-拆卸-重组机制：[CoL₂]→[Co₄L₄]→[Co₇L₁₀]→[Co₁₃L₁₂（L′）₂]→[Co₁₉L₂₀（L′）₂]。它们的演化也表明，有机、无机和原位生成配体的协同作用，以及金属离子的不同配位几何形状，对奇数和高核配位聚合物的形成起着指向性作用。磁性分析表明，反铁磁耦合在磁体中起主导作用。

附：英文原文

Title: Tandem assembly-disassembly-reassembly of hierarchical Co19 coordination cluster facilitated by in-situ ligand transformation: Crystallography and ESI-MS revealed mechanism

Author: anonymous

Issue&Volume: 2025-07-04

Abstract: Odd-numbered and high-nuclearity coordination clusters are extremely rare, yet they represent an intriguing subclass lacking regular repeating building blocks and high structural symmetry for understanding self-assembled multiatomic systems. Herein, the largest cobalt and polydentate ligand based cluster featuring odd-nuclearity, namely [Co19(HL1)8(L1)12(L′)2(Ac)4]·10CH3CH2OH·6H2O (1, H2L1 = 1H-benzo[d]imidazole-2-yl)methanol, HL′ = 1H-benzo[d]imidazole), was obtained with in-situ ligand transformation from H2L1 to L′. It features a hierarchical trilayer and void-cage inside structure, consisting of central disc-shaped [Co7L10] core with two [Co6] rings on both sides. ESI-MS of crystal 1 yields a series of more than sixteen fragments, all featuring an integrated [Co19] core, suggesting stability of the polynuclear cluster in solution. During increased in-source energy from 0 to 100 eV, all MS peaks shifted to a lower m/z range, but the [Co19] core remained intact, excepting for the stepwise elimination of up to three Ac- anions or three L1 linkers. PXRD tracking of the reaction sediments showed the formation of a key precursor of [Co4L4] cubane at 3 h, and its content decreased at 6 h and vanished at 12 h, followed by the appearance of crystals 1 by generation of a clear solution at 18 h, suggesting an initial cluster assembly-disassembly process. ESI-MS spectra analysis of both reaction sediment and solution further identify the existence of other crucial higher-nuclearity reassembled fragments of [Co7L10] disk and its expansion of [Co13L12(L′)2]. A probable tandem assembly-disassembly-reassembly mechanism is put forward as [CoL2]→[Co4L4]→[Co7L10]→[Co13L12(L′)2]→[Co19L20(L′)2]. Their evolution also indicated the ingenious synergy of coexisting organic, inorganic and in-situ generated ligands, along with diverse coordination geometries of metal ions, plays a directional role in formation of odd-numbered and high-nuclearity coordination clusters. Magnetism analysis revealed antiferromagnetic coupling play dominated role in the cluster.

DOI: 10.1016/j.cjsc.2025.100659

Source: http://cjsc.ac.cn/cms/issues/827