Linear regression analysis of molecular energy properties for poly heterocyclic compounds

Energy properties (total electronic energies, kinetic energies, atomization energies, zero point energies, thermal energies, and thermal enthalpies) of several linear homologous of poly heterocyclic compounds have been calculated using HF and B3LYP in conjunction with 6-31G(d) basis set. Calculated energy properties of each family of homologous series have been employed to generate a fit function versus the total number of electrons as well as the number of repeating units. The observed perfect linearity of regression lines of every homologous compound can be used to predict estimated energy properties of homologous from the regression parameters determined for a set of known energy properties of smaller compounds which belong to the same homologous series. From these values, extrapolated energy properties of even large molecules are accessible within chemical accuracy. Also, it has been found that, except for absolute values, the trends of various energy properties remain the same, at two levels of calculation. The success of the linear fittings with respect to either the number of electrons or the number of repeating units is insensitive to the inclusion of electron correlation.