Quantitative structure-property relationships (QSPRs) on direct photolysis quantum yields of PCDDs.

By the use of partial least squares (PLS) method and 16 fundamental quantum chemical descriptors computed by PM3 Hamiltonian, quantitative structure-property relationships (QSPRs) were obtained for direct photolysis quantum yields of selected polychlorinated dibenzo-p-dioxins (PCDDs). Direct photolysis quantum yields for PCDDs without experimental quantum yield values were predicted. The QSPR results showed that it was mainly the number of chlorine atoms bonded to the parent structure, the largest positive atomic charge on a chlorine atom, the dipole moment, and the frontier molecular orbital energies (Ehomo and Elumo) that determine the direct photolysis quantum yields of the PCDDs. Increasing the number of chlorine atoms, dipole moment, and the largest positive atomic charge on a chlorine atom, leads to decrease of photolysis quantum yields. Increasing Elumo, Ehomo and Elumo - Ehomo values lead to increase of log Y values.