Macrocycles and Coordination Polymers Derived from Self-Complementary Tectons Based on N-Containing Boronic Acids

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• 作者：Domingo Salazar-Mendoza ; Jorge Cruz-Huerta ; H. H枚pfl ; Ir谩n F. Hern谩ndez-Ahuactzi ; Mario Sanchez
• 刊名：Crystal Growth & Design
• 出版年：2013
• 出版时间：June 5, 2013
• 年：2013
• 卷：13
• 期：6
• 页码：2441-2454
• 全文大小：758K
• 年卷期：v.13,no.6(June 5, 2013)
• ISSN：1528-7505

文摘

A series of N-containing boronic esters have been prepared by combination of 3-pyridineboronic acid (3-pyba), 4-pyridineboronic acid (4-pyba), and 5-isoquinolineboronic acid (5-iqba) with ethanol, 1,2-ethanediol, and 1,3-propanediol. The resulting self-complementary tectons (SCTs) assembled further through N 鈫?B bond formation to give one tetranuclear macrocyclic and four one-dimensional polymeric boron complexes: [(3-py)B(OEt)₂]₄ (2), [(3-py)B(OCH₂CH₂O)]_n (3), [(4-py)B(OEt)₂]_n (4), [(5-iq)B(OCH₂CH₂O)]_n (6), and [(5-iq)B(OCH₂CH₂CH₂O)]_n (7). In conjunction with the previously reported pentadecanuclear boroxine cage (1) and high-dimensional assemblies derived from pentaerythritol, [(4-py)B(OCH₂)₂C(CH₂O)₂B(4-py)]_n路4nEtOH路nH₂O路nC₇H₈ (5), and [(5-iq)B(OCH₂)₂C(CH₂O)₂B(5-iq)]_n路nEtOH (8), it was shown that a single class of self-complementary boron-based tectons can give a varied series of finite and infinite supramolecular aggregates. A comparative structural characterization of boron complexes 2鈥?b>4 and 6鈥?b>7 by single-crystal X-ray diffraction analysis and quantum-chemical calculations revealed that the corresponding SCTs could have been organized in all cases in the form of tetrameric macrocycles, as it occurred for 2, indicating that intermolecular noncovalent interactions during crystallization probably play a significant role in the output of the assembly process and influence the formation of supramolecular isomers. This observation was supported by a comparison of the molecular geometries of a series of tetranuclear macrocyclic and related linear oligomeric boronic esters derived from 3-pyba, 4-pyba, and 5-iqba, whose structures have been optimized by quantum-chemical calculations at the (B3LYP/cc-pVDZ) level of theory. The calculated structure of [(3-py)B(OEt)₂]₄ was in good agreement with the structure obtained experimentally by single-crystal X-ray diffraction analysis. For the cyclo-tetramers derived from 3-pyba and 5-iqba, all common conformers known from calixarene chemistry have been analyzed (cone, 1,3-alternate, 1,2-alternate, and partial cone), showing that the boronic ester group has a significant influence on their relative stability.