Multicomponent Hydrogen-Bonding Salts Constructed from Tris(2-benzimidazylmethyl)amine and Various Carboxylic Acids: Role of Benzimidazolium-Carboxylate Supramolecular Heterosynthons on Network Assembly

A survey of the Cambridge Structural Database (CSD) indicates that 79% of complexes that contain both imidazole and carboxyl groups generate imidazolium-carboxylate supramolecular heterosynthons rather than carboxyl or imidazole supramolecular homosynthons. In the absence of other competing factors, the occurrence of such heterosynthons is increased to 100%. This observation is further supported by the crystal structures of seven new complexes that contain tris(2-benzimidazylmethyl)amine (TBMA) and a variety of carboxylic acids, including benzoic acid (HBA), p-methoxybenzoic acid (HPMBA), phthalic acid (H2PA), terephthalic acid (H2TPA), isophthalic acid (H2PIA), trimesic acid (H3TMA), and pyromellitic acid (H4PMA). In all seven complexes, (H2TBMA)·(BA)2·DMF (1), (HTBMA)·(PMBA)·(TBMA)·(HPMBA)2·2DMF·H2O (2), (HTBMA)·(H2TBMA)·(HPA)·(PA)·3DMF·H2O (3), (HTBMA)2·(TPA)·2DMF (4), (HTBMA)2·(PIA)·2DMF (5), (H2TBMA)·(HTMA)·0.5DMF·H2O (6), and (HTBMA)2·(H2PMA)·2DMF·H2O (7), proton transfer occurs from acid to aromatic nitrogen of benzimidazole (partial proton transfer for 3, 6, and 7). Analysis of the H-bonding synthons and their effect on crystal packing is also presented in the context of crystal engineering and host−guest chemistry. In the structure of 1, discrete acid/base hexamers are formed via synthons III, V, and VI, while in 2−5, self-recognition via synthons IV, V, and VI results in one-dimensional (1-D) chains, and these structures are extended to high-dimensional architectures (two-dimensional (2-D) structures in 3 and three-dimensional (3-D) structures in 2, 4, and 5) via additional C−H···O, C−H···π and π···π interactions. Interestingly, salts 6 and 7 display the 3-D supramolecular networks via synthons III, IV, V, and VI, which have 1-D channels that are occupied by DMF guests.

对剑桥结构数据库（Cambridge Structural Database, CSD）的调研显示，同时含有咪唑与羧基的配合物中，有79%会形成咪唑鎓-羧酸酯类超分子异合成子，而非羧基或咪唑类超分子同合成子。若无其他竞争因素存在，此类异合成子的生成占比可提升至100%。这一结论可通过7种新型配合物的晶体结构得到进一步验证，这些配合物均由三(2-苯并咪唑甲基)胺（tris(2-benzimidazylmethyl)amine, TBMA）与多种羧酸构筑，包括苯甲酸（HBA）、对甲氧基苯甲酸（HPMBA）、邻苯二甲酸（H2PA）、对苯二甲酸（H2TPA）、间苯二甲酸（H2PIA）、均苯三甲酸（H3TMA）以及均苯四甲酸（H4PMA）。该7种配合物分别为：(H₂TBMA)·(BA)₂·DMF（1号）、(HTBMA)·(PMBA)·(TBMA)·(HPMBA)₂·2DMF·H₂O（2号）、(HTBMA)·(H₂TBMA)·(HPA)·(PA)·3DMF·H₂O（3号）、(HTBMA)₂·(TPA)·2DMF（4号）、(HTBMA)₂·(PIA)·2DMF（5号）、(H₂TBMA)·(HTMA)·0.5DMF·H₂O（6号）以及(HTBMA)₂·(H₂PMA)·2DMF·H₂O（7号）。在全部7种配合物中，均发生了质子从羧酸向苯并咪唑芳族氮原子的转移（其中3号、6号和7号为部分质子转移）。本文还结合晶体工程与主客体化学的研究背景，对氢键合成子及其对晶体堆积的影响进行了分析。在1号配合物的晶体结构中，通过合成子III、V和VI形成了离散的酸碱六聚体；而在2~5号配合物中，通过合成子IV、V和VI的自识别作用形成了一维（1-D）链状结构，这些结构还可通过额外的C−H···O、C−H···π及π···π相互作用进一步拓展为高维架构：3号配合物为二维（2-D）结构，2号、4号及5号配合物则为三维（3-D）结构。值得注意的是，6号和7号盐类配合物通过合成子III、IV、V和VI构筑了三维超分子网络，其内部存在被DMF客体分子填充的一维通道。