二噁英结构与正辛醇-水分配系数相关性的密度泛函理论

Study on the relationship between dioxin structures and n-octanol-water partition coefficients using density functional theory (DFT)

为精确描述二噁英分子的电子结构及其定量结构/性质相关关系(QSPRs),运用密度泛函理论,在B3LYP/6-311G**水平上,分别对多氯二苯并对二噁英(PCDDs)和多氯二苯并呋喃(PCDFs)进行了优化计算.相应量子化学参数,即平均分子极化率(α),熵(S),极化率和四极矩的张量分量(αxx,αyy,αzz和Qxx,Qyy,Qzz)用于该类化合物辛醇-水分配系数的QSPR研究,构建了2个单变量和1个双变量模型,其决定系数R2分别为0.962、0.950和0.951;其显著性检验因子F分别为509.759、379.498和186.234.PCDD/Fs在辛醇相-水相间的分配性质主要与分子体积因素有关,而电性因素的影响较小;不同模型预测值间的差异与模型中预测变量本身性质和实验值的有限性有关.经比较,本研究中所建立的3个QSPRs模型尽管只有1个或2个变量,但其结果与复杂的偏最小二乘分析(PLS)相近.

Density functional theory （DFT） was applied to precisely characterize the electronic structures of dioxins as well as their quantitative structure- property relationships （QSPRs）. The electronic structures of all polychlorinated dibenzo-p-dioxins （PCDDs） and dibenzofurans （PCDFs） were fully optimized at the level of B3LYP/6-31 IG ＊ ＊ . The corresponding quantum parameters, viz. the mean polarizability（a）, entropy（S） as well as the tensor components of polarizability and quadrupole moment （αXX ,αyy, αzz and Qxx, Qyy, Qzz ） were used to study the octanol-water partitioning property with QSPRs. Two single variable models and one double variable model are proposed, for which the determination coefficients are 0. 962, 0. 950 and 0. 951, respectively, and the Fischer variance ratios are 509. 759, 379. 498 and 186. 234. The partitioning of PCDD/Fs between lipid and water phase is mainly related to the molecular volume while the effects of molecular charge distribution are much less important. A limited number of experimental values and the characteristics of variables in different QSPRs govern the differences of the predicted values. By comparison, the performance of the proposed QSPRs is close to that derived from the complex partial least squares （PLS） analysis, even though only one or two variables are involved.