Institute for Theoretical Chemistry, Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas, USA.
J Phys Chem A. 2013 Feb 21;117(7):1670-84. doi: 10.1021/jp312073q. Epub 2013 Feb 7.
In B(n)N(n) cages or tubes, when the quasi-borazine rings are attached to each other through a pair of common atoms of B and N, the bonding structure is named class A. On the other hand, there are some B(n)N(n) rings including a covalent bond between two atoms of B and N, which are named class B. In all previous studies, both reports of synthesis and theoretical calculation of boron nitride tubes and cages, the quasi-borazine units are attached together like class A. There are no theoretical or experimental reports from class B compounds except for a brief study in our previous works (Struct. Chem. 2012, 23, 551-580; J. Phys. Chem. C 2010, 114, 15315.). In this study, we have used two kinds of boron nitride rings from a twisted BN sheet in the same chirality created by different mechanisms. For (4, 4) chirality, the molecules B(16)N(16) and B(15)N(15) are found to respectively represent class A and B, and for (5, 5) chirality the molecules B(20)N(20) and B(18)N(18) are respectively again of class A and B. The structure of class A rings is similar to boron nitride tubes, but we have shown that it is impossible to produce a macromolecule of class B form as tubes or cages, because there is much more instability and intermolecular tension in macro forms of class B. This is the main reason that the class B molecules are rare and, because of their small size, have not yet been synthesized, although we have some suggestions for the synthesis of these kinds of molecules. The stability and electromagnetic properties with hybrid density functional theory using the EPR-III and EPR-II basis sets for explanation of hyperfine parameters and spin densities, electrical potential, and isotropic Fermi coupling constant of these rings have been studied by the nonbonded interaction models. Normal mode analyses including aromaticity have been investigated by using the nucleus independent chemical shift values at the ring center. Interaction energy and gain in energy aid in describing the stability that is promoted upon gradual binding with molecular hydrogen, and a linear relationship occurred between them.
在 B(n)N(n)笼或管中，当准硼氮嗪环通过 B 和 N 的一对公用原子彼此连接时，键合结构命名为 A 类。另一方面，有一些 B(n)N(n)环包含 B 和 N 两个原子之间的共价键，这些环命名为 B 类。在以前的所有研究中，硼氮化物管和笼的合成和理论计算报告都将准硼氮嗪单元像 A 类一样连接在一起。除了我们之前的工作（Struct. Chem. 2012, 23, 551-580; J. Phys. Chem. C 2010, 114, 15315.）中简短的研究之外，没有 B 类化合物的理论或实验报告。在这项研究中，我们使用了由两种不同机制产生的同手性扭曲 BN 片上的两种氮化硼环。对于（4,4）手性，发现分子 B(16)N(16)和 B(15)N(15)分别代表 A 类和 B 类，对于（5,5）手性，分子 B(20)N(20)和 B(18)N(18)再次分别代表 A 类和 B 类。A 类环的结构类似于氮化硼管，但我们已经表明，不可能像管或笼一样产生大分子形式的 B 类，因为大分子形式的 B 类存在更多的不稳定性和分子间张力。这是 B 类分子很少见的主要原因，而且由于它们的体积小，尚未被合成，尽管我们对这些分子的合成有一些建议。使用 EPR-III 和 EPR-II 基组的混合密度泛函理论对非键相互作用模型进行了稳定性和电磁特性研究，以解释这些环的超精细参数和自旋密度、电势能和各向同性费米偶合常数。通过核独立化学位移值在环中心研究了包括芳香性在内的正则模态分析。通过与分子氢逐渐结合促进的稳定性的相互作用能和能量增益来描述稳定性，它们之间存在线性关系。
