One- and Two-Step Self-Assembly Processes in Zn(II) Supramolecular Frameworks with Ditopic Bis(pyrazolyl)methane Ligands. Chiral Recognition and Formation of Cyclic Helicates

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• 作者：Gema Dur谩 ; M. Carmen Carri贸n ; F茅lix A. Jal贸n ; Blanca R. Manzano Ana M. Rodr铆guez
• 刊名：Crystal Growth & Design
• 出版年：2015
• 出版时间：November 4, 2015
• 年：2015
• 卷：15
• 期：11
• 页码：5174-5182
• 全文大小：635K
• ISSN：1528-7505

文摘

The new ligands bis(pyrazol-1-yl)(pyridine-3-yl)methane (bpzm3py, 1) and bis(3,5-dimethylpyrazol-1-yl)(pyridine-3-yl)methane (bpz*m3py, 2) have been synthesized. Box-like cyclic dimers have been obtained by reaction of the ligands with Zn(NO₃)₂, namely, [Zn(NO₃)₂L]₂ (L = 1, complex 3; L = 2, complex 4), after the self-assembly of two metal centers and two ligands in a head-to-tail fashion. In 3 and 4 the pyridine rings exhibit planar chirality and the two pR,pR and pS,pS enantiomers coexist in the crystal. A two-step self-assembly process using 3 as an SBU and sodium 1,4-benzenedicarboxylate (Na₂BDC) as a linker leads to the formation of hexanuclear cyclic helicates with a distorted trigonal prism form [Zn₂(BDC)(1)₂(H₂O)₄]₃(BDC)₃ (5) constituted by cyclic dimers and 渭²,魏²-BDC connectors that are oriented diagonally. The chiral recognition that is observed means that the three dimers of the helicate have the same chirality. In the 3-D structure, chains of helicates of the same chirality are formed and these interdigitate with chains of opposite chirality connected by hydrogen bonds and through a column of 蟺鈥撓€ stacking interactions involving alternate pyridine and benzene rings.