Introducing “Colored” Molecular Topology by Reactivity Indices of Electronegativity and Chemical Hardness

Within the context of conceptual density functional theory chemical reactivity definitions of electronegativity (EN) and chemical hardness (HD), nine forms of their finite difference are expressed in order to consider the global “coloring” of the molecular topology with respect to their symmetry centers (atomic centers or bonding centers), according to the so-called Timişoara–Parma rule. The resulting parabolic-reactive energy in terms of EN and HD is compared with the bond topological Wiener index for short list of PAH (poly-aromatic hydrocarbons) selected as paradigmatic structures for validating the new reactivity descriptors based on topological quantities.