Encapsulation of ArnComplexes by Calix[4]arene: Endo- vs. Exo-Complexes
Encapsulation of ArnComplexes by Calix[4]arene: Endo- vs. Exo-Complexes
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Calix[4] 芳烃对 Arn 复合物的封装：Endo 复合物与 Exo 复合物
DOI：
10.1039/b927441c
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
and S. S. Xantheas
中科院分区：
文献类型：
--
作者：
T. Ebata;N. Hontama;Y. Inokuchi;T. Haino;E. Apra;and S. S. Xantheas
通过激光诱导荧光光谱、质量选择共振双色双光子电离 (2C-R2PI) 光谱、碎片检测红外光解离 (FDIRPD) 光谱以及 MP2 和 CCSD(T) 理论水平的高级第一原理电子结构计算，研究了杯 [4] 芳烃 (C4A)-Arn 配合物的结构。 C4A具有非常高的与稀有气体原子形成范德华配合物的能力。对于 C4A-Ar 二聚体，观察到两种异构体。主要物种显示出其带源相对于单体的 45 cm−1 红移，而次要物种的红移为 60 cm−1。通过 2C-R2PI 光谱和 FDIRPD 光谱确定主要物质的结合能在 350–2250 cm−1 范围内。量子化学计算中还确定了两种异构体，具体取决于 Ar 原子是位于 C4A 内部 (endo) 还是外部 (exo)。我们提出了一种方案，基于较小基组的 CCSD(T) 计算以及较小模型体系苯-Ar 和苯酚-Ar 的 CCSD(T)/MP2 能量比，推导出 C4A-Ar 配合物的 CCSD(T)/完全基组 (CBS) 质量结合能，其中 CCSD(T) 理论水平收敛于实验确定的结合能。我们在 CCSD(T)/CBS 理论水平上对 C4A-Ar 内复合物和内复合物的结合能的最佳计算估计分别为 1560 cm−1 和 510 cm−1。对于 C4A-Ar2 三聚体，计算结果支持两种近等能异构体的存在：一种是 {2 : 0} 内复合物，其中 Ar2 二聚体被封装在 C4A 空腔内，另一种是 {1 : 1} 内外复合物，其中一个 Ar 位于 C4A 空腔内部，另一个位于 C4A 空腔外部。然而，实验证据强烈表明观察到的物种是 {2 : 0} 内复合物。内结构基序也被建议用于较大的 C4A-Arn 复合物，因为观察到复合物的系统红移与结合的 Ar 原子数量表明 Arn 复合物被封装在 C4A 空腔内。内复合物结构的形成归因于在扩展区域复合物形成过程中与C4A相互作用的各向异性。
The structure of the calix[4]arene(C4A)–Arn complexes has been investigated by laser induced fluorescence spectroscopy, mass-selected resonant two-color two-photon ionization (2C-R2PI) spectroscopy, fragment detected IR photodissociation (FDIRPD) spectroscopy, and high level first principles electronic structure calculations at the MP2 and CCSD(T) levels of theory. C4A has a very high ability to form van der Waals complexes with rare gas atoms. For the C4A–Ar dimer two isomers are observed. A major species shows a 45 cm−1 red-shift of its band origin with respect to the monomer, while that of a minor species is 60 cm−1. The binding energy of the major species is determined to be in the range of 350–2250 cm−1 from 2C-R2PI spectroscopy and FDIRPD spectroscopy. Two isomers are also identified in the quantum chemical calculations, depending on whether the Ar atom resides inside (endo) or outside (exo) the C4A. We propose a scheme to derive CCSD(T)/Complete Basis Set (CBS) quality binding energies for the C4A–Ar complex based on CCSD(T) calculations with smaller basis sets and the ratio of CCSD(T)/MP2 energies for the smaller model systems benzene–Ar and phenol–Ar, for which the CCSD(T) level of theory converges to the experimentally determined binding energies. Our best computed estimates for the binding energies of the C4A–Ar endo- and endo-complexes at the CCSD(T)/CBS level of theory are 1560 cm−1 and 510 cm−1, respectively. For the C4A–Ar2 trimer the calculations support the existence of two nearly isoenergetic isomers: one is the {2 : 0} endo-complex, in which the Ar2 dimer is encapsulated inside the C4A cavity, and the other is the {1 : 1} endo–exo-complex, in which one Ar resides inside and the other outside the C4A cavity. However, the experimental evidence strongly suggests that the observed species is the {2 : 0} endo-complex. The endo structural motif is also suggested for the larger C4A–Arn complexes because of the observed systematic red-shifts of the complexes with the number of bound Ar atoms suggesting that the Arn complex is encapsulated inside the C4A cavity. The formation of the endo-complex structures is attributed to the anisotropy of the interaction with C4A during the complex formation in the expansion region.