Hu Jiwei, Eriksson Lars, Bergman Ake, Kolehmainen Erkki, Knuutinen Juha, Suontamo Reijo, Wei Xionghui
Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, 100871 Beijing, PR China.
Chemosphere. 2005 May;59(7):1033-41. doi: 10.1016/j.chemosphere.2004.11.028. Epub 2005 Jan 7.
Polybrominated diphenyl ethers (PBDEs) are widely used as additive flame retardants and quantities in the environment are on the rise. Because they are structurally related to polychlorinated biphenyls and also to thyroid hormones, there is serious concern that PBDEs may pose a danger to human health. Knowledge of their conformational properties is key to assessing their environmental fate and risk. The conformational properties of PBDEs were investigated by quantum chemical methods including semiempirical self-consistent field molecular orbital (SCF-MO), ab initio SCF-MO and density functional theory (DFT). Conformational analyses of model congeners 2,2',4,6'-tetrabromodiphenyl ether and 2,3,4,4',5,6-hexabromodiphenyl ether, based on energy maps calculated by semiempirical AM1 method, may indicate that all PBDE congeners except those with the tetra-ortho-bromination are conformationally flexible (or soft) due to low energy barriers for interconversion of stable conformers. The results of the conformational analyses are in conformity with recently published X-ray crystallographic data. For comparison with the results of the semiempirical method, higher level ab initio and DFT models were applied as well. The optimized geometries all lie well inside low energy regions on the maps and thus also ascertain the semiempirical calculations. According to computed geometric parameters and net atomic charges, the model B3LYP/3-21G* seemed to give better results than B3LYP/6-31G* and HF/6-31G*.
多溴二苯醚（PBDEs）作为添加型阻燃剂被广泛使用，其在环境中的含量正在上升。由于它们在结构上与多氯联苯以及甲状腺激素相关，人们严重担忧多溴二苯醚可能对人类健康构成威胁。了解它们的构象性质是评估其环境归宿和风险的关键。通过量子化学方法研究了多溴二苯醚的构象性质，这些方法包括半经验自洽场分子轨道（SCF-MO）、从头算SCF-MO和密度泛函理论（DFT）。基于半经验AM1方法计算的能量图，对模型同系物2,2',4,6'-四溴二苯醚和2,3,4,4',5,6-六溴二苯醚进行构象分析，结果可能表明，除了那些具有四邻位溴取代的同系物外，所有多溴二苯醚同系物由于稳定构象之间相互转化的能量壁垒较低，在构象上都是灵活的（或柔软的）。构象分析的结果与最近发表的X射线晶体学数据一致。为了与半经验方法的结果进行比较，还应用了更高水平的从头算和DFT模型。优化后的几何结构都很好地位于能量图上的低能量区域内，因此也证实了半经验计算的结果。根据计算得到的几何参数和净原子电荷，模型B3LYP/3-21G似乎比B3LYP/6-31G和HF/6-31G*给出了更好的结果。
