Key Lab of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan, 250100, People's Republic of China.
J Phys Chem A. 2010 Dec 23;114(50):13122-8. doi: 10.1021/jp109306v. Epub 2010 Nov 19.
The effective enrichment and identification of lowly concentrated polychlorinated biphenyls (PCBs) in the environment is attracting enormous research attention due to human health concerns. Cyclodextrins (CDs) are known to be capable of forming inclusion complexes with a variety of organic molecules. The purpose of this study is to provide theoretical evidence of whether CDs as host molecules can include the guest molecules PCBs to form stable host-guest inclusion complexes, and if so, whether the general infrared and Raman techniques are suitable for the direction of CD-modified PCBs. Focusing on a representative PCB molecule, 2,2',5,5'-tetrachlorobiphenyl (PCB52), we carried out density functional theory calculations and molecular dynamics (MD) simulations on its complexes with α-, β-, and γ-CDs with different host-guest stoichiometry ratios, including 1:1, 1:2, 2:1, and 2:2. On the basis of both the optimized geometries and calculated energy changes raised from encapsulating the guest molecule into the cavities of CDs, the CDs are believed to be suitable hosts for accommodating PCB52 guest molecules. The stability of inclusion complexes depends on both the type of CD and host-guest stoichiometry ratio. MD simulations give a clear picture of the scene on how the PCB52 molecule enters the cavity of β-CD. The vibrational analyses on the 1:1 complexes of CDs provide information for the spectral characterization of the inclusion complexes: Raman spectroscopy can deliver the characteristic bands of PCB52, whereas IR spectroscopy cannot uniquely assign them, implying that Raman spectroscopy is a useful technique for the identification of CD-modified PCBs. The present theoretical results are expected to provide guidance for the relevant experimental research.
由于对人类健康的关注,有效富集和鉴定环境中低浓度多氯联苯(PCBs)引起了极大的研究关注。环糊精(CDs)已知能够与各种有机分子形成包合复合物。本研究旨在提供理论证据,证明 CDs 作为主体分子是否可以包含客体分子 PCB 以形成稳定的主客体包合复合物,如果可以,一般的红外和拉曼技术是否适用于 CD 修饰的 PCB 方向。本研究选择了一种代表性的 PCB 分子,即 2,2',5,5'-四氯联苯(PCB52),我们对其与不同主客体化学计量比的α-、β-和γ-CDs 的复合物进行了密度泛函理论计算和分子动力学(MD)模拟,包括 1:1、1:2、2:1 和 2:2。基于优化的几何形状和从客体分子封装到 CDs 腔中引起的计算能量变化,CD 被认为是容纳 PCB52 客体分子的合适主体。包合物的稳定性取决于 CD 的类型和主客体化学计量比。MD 模拟清楚地描绘了 PCB52 分子进入 β-CD 腔的情景。CDs 1:1 复合物的振动分析为包合物的光谱特征提供了信息:拉曼光谱可以提供 PCB52 的特征带,而红外光谱不能唯一地对其进行分配,这意味着拉曼光谱是鉴定 CD 修饰的 PCB 的有用技术。本研究的理论结果有望为相关实验研究提供指导。
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