In this paper we take photobacterium phosphoreum （T3） as the experimental bacteria, and determine the half-inhibitory concentration （-1gEC50） against the photobacterium phosphoreum of 16 halogenated benzenes. Using B3LYP method of DFT in the Gaussian 03 program, we obtain the structural and thermodynamic descriptors of 16 halogenated benzenes by fully-optimized calculation at the 6-311G＊＊ level. Taking the structural and thermodynamic descriptors as theoretical descriptors, the 2D QSAR model （R2 = 0.983） was established, which can be utilized to predict -lgEC50 of halogenated benzene according to the corrected linear solvation energy theory based on the experimental data of-lgECs0. In addition, the relationship between the toxicity and 3D spatial structure of the compound is studied by comparing the molecular similarity index analysis （CoMSIA） of 3D-QSAR method. By cross validation, the correlation coefficient q2 of CoMSIA model is 0.687, and the conventional correlation coefficient R2 = 0.958. The model is stable and reliable with great predictive ability. The 3D-QSAR model shows that the toxicity of halogenated benzene compound is mainly affected by the characteristics of hydrophobie field of the substituted halogens.
CAO Si-TongWANG XiuLIU Hong-XiaYANG Guo-YingWANG Zun-Yao
Decabromodiphenyl ether （BDE-209）, the major congener in the high volume industrial flame retardant mixture ＂DecaBDE＂, has become a ubiquitous environmental contaminant. In the present work, combined experimental and theoretical studies have been undertaken on the structure and vibrational spectra of BDE-209. The FT-IR （400-4000 cm-1） and FT-Raman spectra （100-4000cm-1） of BDE-209 were recorded, while density functional B3LYP calculations were employed in conjunction with the 6-31G（d） basis set for investigating the corresponding geometric structure and vibrational spectroscopic properties. Besides, the detailed interpretations of fundamental vibrations were performed on the basis of experimental results and potential energy distribution （PED） of the vibrational modes. Optimized structures of the title compound were interpreted and compared with the earlier reported experimental values, which yield good agreement. Finally, the measured and calculated harmonic vibrational wavenumbers were compared with each other, and they were found to be in good accordance.
Toxicities （-lgEC50） of 16 fluorobenzene derivants against vibrio qinghaiensis （Q67） were measured systematically,and their quantum chemistry parameters were calculated at the B3LYP/6-311G＊＊ level. Based on the experimental toxicity data and quantum chemistry parameters,2D-QSAR model was proposed,which was validated by variance inflation factors （VIF）,t-value and cross-validation method. At the mean time,comparative molecular force field （CoMFA） based on molecular simulation was used to investigate the toxicity of fluorobenzene derivants. Furthermore,the intoxicating mechanism of fluorobenzene derivants was discussed. To our interest,2D-QSAR and CoMFA models exhibit good prediction ability,with which the toxicity of similar compounds can be predicted. Finally,toxicities （-lgEC50） of 12 fluorobenzene derivants against vibrio qinghaiensis （Q67） were predicted with these models.
The gas phase thermodynamic properties of 135 polychlorinated xanthones(PCXTs)are calculated using a combination of quantum mechanical computations performed with the Gaussian 03 program at the B3LYP/6-311G**level.It is found that the chlorine substitution pattern strongly influences the thermodynamic properties of the compounds.The thermodynamic properties of congeners with the same number of chlorines also depend on the chlorine substitution pattern,especially for ortho-substituted congeners.PCXT congeners with one phenyl ring fully chlorinated are found to be the least stable among the analogues.The effect of the chlorine substitution pattern is quantitatively studied by considering the number and position of Cl atom substitution(NPCS).The results show that the NPCS model may be used to predict the thermodynamic properties for all 135 PCXT congeners. In addition,the values of molar heat capacities at constant pressure(cp,m)from 200 to 1000 K for PCXT congeners are calculated,and the temperature dependence relation of this parameter is obtained using the least-squares method.
The molecular structures of 135 poly-bromine carbazole （PBCZs） compounds were fully optimized at the B3LYP/6-31G＊ level, and their thermodynamic properties at 98.15 K, 1.013 ×105 Pa were consequently obtained. Based on our isodesmic reaction, standard formation heat （ΔfHθ） and standard formation free energy （ΔfGθ） of PBCZs were calculated. Furthermore, the relationship between thermodynamic parameters and the position and number （NPBS） of Brsubstitution were also discussed. To our interest, a good dependence can be observed among entro- py （Sθ）, ΔfHθ, ΔfGθ and NPBS. Ultimately, the theoretical stability order of isomers can be decided judging from the ΔfGθ value.
The thermodynamic properties of xanthone（XTH） and 135 polybrominated xanthones（PBXTHs） in the standard state have been calculated at the B3LYP/6-31G＊ level using Gaussian 03 program.The isodesmic reactions were designed to calculate the standard enthalpy of formation（△fHθ） and standard free energy of formation（△fGθ） of PBXTH congeners.The relations of these thermodynamic parameters with the number and position of Br atom substitution（NPBS） were discussed,and it was found that there exist high correlation between thermodynamic parameters（entropy（Sθ）,△fHθ and △fGθ） and NPBS.According to the relative magnitude of their △fGθ,the relative stability order of PBXTH congeners was theoretically proposed.The relative rate constants of formation reactions of PBXTH congeners were calculated,Moreover,the values of molar heat capacity at constant pressure（Cp,m） from 200 to 1000 K for PBXTH congeners were also calculated,and the temperature dependence relation of them was obtained,suggesting very good relationships between Cp,m and temperature（T,T^1 and T^2） for almost all PBXTH congeners.
