3-DIMENSIONAL MOLECULAR DESCRIPTORS BASED ON ELECTRON CHARGE-DENSITY WEIGHTED GRAPHS

Electron charge density calculated from quantum-chemical methods is used as vertex weight in molecular graphs. One graph theoretical index is obtained by using the Randic-type invariant in the present approach. The new index contain information on 3D features of molecules, and it is discriminative between geometrical isomers, such as cis-trans alkenes and between conformers. This index is used in quantitative structure-property relationships with boiling points of alkenes, and its performance is compared to the valence molecular connectivity index of Kier and Hall. Another index considering a correction to include the influences of different hydrogen atoms in the molecule is also proposed. Both novel indexes are more isomer sensitive than 2D molecular connectivity indexes, and the statistical analysis shows that correlations obtained with the 3D molecular descriptors an better than with the 2D ones.