Supramolecular Loop-Chain Network of Pillared Layers via 4,4‘-Bipyridine

A new structural motif occurs in the organic salt of formula {[H3bta]2[H2-4,4‘-bpy]} 1 where stacks of infinite pillared rhombically distorted square grid networks are interpenetrated by the same pillared networks in a loop−chain modus. Interestingly, the X-ray structure of 1 reveals two [H3bta]- monoanions of piromellitic acid (benzene-1,2,4,5-tetracarboxylic acid, H4bta) and one [H2-4,4‘-bpy]2+ cation in the asymmetric unit. Each H3bta- unit builds up two different hydrogen-bonded sheets (A and B) which are parallel to the ab-plane. The [H2-4,4‘-bpy]2+ cation acts as a pillar along the c-axis linking nonadjacent A and B sheets to afford an extended three-dimensional network.化学式为{[H₃bta]₂[H₂-4,4'-bpy]} 1的有机盐中存在一种新型结构基元：无限柱撑菱形畸变方格网格网络的堆叠体以环链模式被同种柱撑网络所互穿。值得注意的是，该化合物1的X射线晶体结构显示，其不对称单元内包含两个属于均苯四甲酸（piromellitic acid，即苯-1,2,4,5-四羧酸，H₄bta）的[H₃bta]-单阴离子，以及一个[H₂-4,4'-bpy]²+阳离子。每个H₃bta-单元可构筑出两种平行于ab平面的氢键片层（分别标记为A与B）。[H₂-4,4'-bpy]²+阳离子作为柱撑单元沿c轴连接非相邻的A、B片层，最终形成拓展的三维网络结构。