Extended energy and its dependence on molecular structure

The extended energy (Eex) is a vertex degree based and spectrum-based molecular structure descriptor, shown to be well correlated with a variety of physicochemical molecular properties. We investigate the dependence of Eex on molecular structure and establish its basic characteristics. In particular, we show how Eex is related with the geometric-arithmetic (GA) topological index. Our main finding is that the difference between Eex and the total π-electron energy is linearly proportional to the difference between the number of edges and the GA index.