Syntheses and Structures of Isomeric Diaminotriazinyl-Substituted 2,2′-Bipyridines and 1,10-Phenanthrolines

Isomeric 2,2′-bipyridines 4a−6a and 1,10-phenanthrolines 7a−9a with two diaminotriazinyl (DAT) substituents were synthesized to explore their dual ability to direct association by the chelation of metals and the characteristic hydrogen bonding of DAT groups. Crystals of compounds 4a−6a and 7a−9a were grown under diverse conditions, and their structures were solved by X-ray crystallography. Analysis revealed multiple shared features analogous to those observed in the structures of simpler DAT-substituted pyridines 1−3. For example, the bipyridines and phenanthrolines favor flattened conformations except in the cases of compounds 8a and 9a, where the patterns of substitution prevent the DAT groups from lying in the plane of the phenanthroline core. As expected, the DAT groups form approximately coplanar hydrogen bonds according to standard motifs I−III, which play a key role in directing molecular organization. However, the structures of simple pyridines 1−3, which favor efficiently packed chains and sheets, differ predictably from those of bipyridines 4a−6a and phenanthrolines 7a−9a in two ways: (1) The larger number of DAT groups in compounds 4a−9a typically leads to complex three-dimensional networks held together by a larger number of hydrogen bonds per molecule, and (2) the need to respect multiple directional interactions prevents compounds 4a−9a from forming closely packed structures, and significant quantities of guests are included. Together, these observations confirm the effectiveness of incorporating special groups such as DAT within more complex molecular structures to control association according to reliable patterns. Bipyridines 4a−6a and phenanthrolines 7a−9a promise to be particularly rich sources of new supramolecular chemistry because they have well-defined molecular topologies and a dual ability to direct association by chelating metals and by engaging in multiple hydrogen bonds according to reliable patterns.

合成了带有两个二氨基三嗪基（diaminotriazinyl, DAT）取代基的异构2,2'-联吡啶类化合物4a−6a与1,10-菲咯啉类化合物7a−9a，以探究其同时通过金属螯合作用与DAT基团特征氢键作用调控分子组装的双重能力。在多种不同条件下培养了化合物4a−6a与7a−9a的单晶，并通过X射线晶体学解析了其晶体结构。结构分析显示，这类化合物与结构更简单的DAT取代吡啶类化合物1−3的晶体结构存在诸多共通特征。例如，除化合物8a与9a外，联吡啶与菲咯啉类化合物均倾向于采取平面构象；在8a和9a中，取代模式使得DAT基团无法与菲咯啉母核共平面。如预期一致，DAT基团按照标准基序I−III形成近似共平面的氢键作用，这类氢键在调控分子组装过程中发挥关键作用。然而，倾向于形成紧密堆积链与层状结构的简单吡啶类化合物1−3，与联吡啶4a−6a及菲咯啉7a−9a的晶体结构存在两处可预测的差异：其一，化合物4a−9a所含DAT基团数目更多，通常会形成由单分子上更多氢键共同维系的复杂三维网络；其二，需兼顾多重方向性相互作用的要求，使得化合物4a−9a无法形成紧密堆积结构，进而容纳了大量客体分子。综上，上述实验结果证实了在更复杂的分子结构中引入DAT等特殊基团，可通过可靠的作用模式精准调控分子组装过程。联吡啶4a−6a与菲咯啉7a−9a具有明确的分子拓扑结构，且同时具备通过金属螯合与可靠氢键模式参与多重氢键作用调控组装的双重能力，因此有望成为新型超分子化学研究的优质体系。