sdarticle2

Computational note
Electronic dipole polarizabilities of polychlorinated dibenzofurans and semiempirical PM6level performance
Andrea Alparone,Vito Librando *
Research Centre for Analysis,Monitoring and Minimization Methods of Environmental Risk,Department of Chemistry,University of Catania,viale A.Doria 8,Catania I-95125,Italy
Polychlorinated dibenzofurans (PCDFs)are widespread and per-sistent environmental contaminants [1].Electronic dipole polariz-abilities (a )of PCDFs were previously computed at the B3LYP level with cc-pVDZ,6-31G Ãand 6-31G ÃÃbasis sets in order to elucidate the effect of the substituent position on the congener specific tox-icity [2,3]and aqueous solubility [4].Recently,semiempirical PM6method [5]has been implemented in MOPAC 2007package [6],giving satisfactory estimates of molecular properties such as heats of formation [5]and electronic a values [7,8].
This work is principally concerned on the validation of the PM6method in the determination of a values,focusing attention on DF and the 135PCDF congeners (Fig.S1of the Supporting Material).Static a ij (i,j =x ,y ,z )components were calculated at the AM1,PM3and PM6levels.Additionally,we computed a ij values for DF and its octacloro substituted congener at the HF,MP2and PBE0levels with aug-cc-pVDZ basis set on the B3LYP/6-31G ÃÃgeometry.Present computations were performed with MOPAC 2007[6]and PC GAMESS [9,10]programs.Calculated average polarizability,h a i ¼1=3ða xx þa yy þa zz Þ,and polarizability anisotropy,D a ¼
f 1½ða xx Àa yy Þ2þða xx Àa zz Þ2þða yy Àa zz Þ2þ6ða 2xy þa 2
xz þa 2yz Þ g 1=2,are given in Tables S1–S3of the Supporting Material.The results show that PM6is noticeably superior to both the commonly em-ployed semiempirical AM1and PM3methods,reproducing the PBE0/aug-cc-pVDZ (and also MP2/aug-cc-pVDZ)h a i values of DF and 1,2,3,4,5,6,7,8-OCDF within 5a.u.(2–3%)and D a data within 8–11a.u.(3–8%),geometrical effects (PM6vs.B3LYP/6-31G ÃÃ)being almost negligible.Note that the corresponding deviations for h a i obtained using the AM1,PM3and B3LYP/6-31G ÃÃ[3]data are substantially larger,being 36–94a.u.(25–34%),41–76a.u.(27–28%),24–47a.u.(16–17%),respectively,while those for D a are 22–25a.u.(9–20%),16–43a.u.(12–18%)and 11–14a.u.(4–11%),respectively.However,least-mean squared fitting linear relationships between the semiempirical and B3LYP/6-31G ÃÃh a i and D a data (See Figs.S2and S3of the Supporting Material)are
satisfactory (r 2=0.97–1.00).As can be appreciated from Figs.S4and S5of the Supporting Material,on passing from PM6to AM1(PM3),h a i and D a values decrease and increase by 21–33%(26–28%)and 13–31%(19–23%),respectively.These discrepancies are principally originated from differences in the out of the plane polarizability component.Due to its relatively low computational cost and good accuracy,PM6is a promising method for the predic-tion of a of large p -conjugated systems and is particularly indi-cated for QSPR studies.Acknowledgement
Work partially supported by MIUR,Rome.Appendix A.Supplementary data
Supplementary data associated with this article can be found,in the online version,at doi:10.1016/j.theochem.2008.09.023.References
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[6]J.J.P.Stewart,MOPAC 2007,Stewart Computational Chemistry,Colorado Springs,CO,USA,
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M.W.Schmidt,K.K.Baldridge,J.A.Boatz,S.T.Elbert,M.S.Gordon,J.H.Jensen,S.Koseki,N.Matsunaga,K.A.Nguyen,S.J.Su,T.L.Windus,M.Dupuis,J.A.Montgomery,put.Chem.14(1993)1347.
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A.A.Granovsky,PC GAMESS version 7.0,Available from:<http://classic.chem.msu.su/gran/gamess/index.html/>.
0166-1280/$-see front matter Ó2008Elsevier B.V.All rights reserved.doi:10.1016/j.theochem.2008.09.023
*Corresponding author.Tel.:+39957385201;fax:+3995580138.E-mail address:vlibrando@unict.it (V.Librando).Journal of Molecular Structure:THEOCHEM 894(2009)
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