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JP15

Similarity of frontier orbitals

�›Yoshihiro Mizukami�iFaculty of Liberal Arts and Education, Shiga University�j

It is well known that frontier orbitals of molecules are important to understand chemical reactivity. We have published papers on relations between frontier electron densities and toxicities of dioxins and dibenzofurans. In this work, we investigate the relations between frontier orbital similarities and toxicities of dibenzofurans. Highest occupied molecular orbitals (HOMO) of 136 congeners of dibenzofurans are calculated by ab initio Hartree-Fock molecular orbital method. HOMO of 2,3,7,8-Tetrachlorinated dibenzofuran (2,3,7,8-T4CDF) is used as reference orbital to estimate the frontier orbital similarity, which is overlap integral between HOMO of 2,3,7,8-T4CDF and HOMO of the other dibenzofuran. We have found that frontier similarities of dibenzofurans are affected by the orbital symmetry of HOMO of the reference molecule. We also define atomic similarity of frontier orbital. Multivariate statistical analysis, especially, principal component analysis is performed for the data sets of atomic similarities ofdibenzofurans. There is a correlation between principal component scores of the first principal component and toxicities of dibenzofurans.