Edge-Connectivity Indices in QSPR/QSAR Studies. 2. Accounting for Long-Range Bond Contributions
Ernesto Estrada · Journal of Chemical Information and Computer Sciences · 1999
A novel graph theoretical polynomial, P ε ( G, x ), counting the edge connectivity is introduced. The first derivative of this polynomial evaluated for x = 0 is equal to the edge-connectivity index of the molecular graph. A series of edge-connectivity indices modified to include long-range bond contributions, ε c ( x ), are obtained by using values of x different from zero. These indices form three independent (orthogonal) groups containing different structural information as proved by the principal component analysis. The use of the ε c ( x ) indices in QSPR studies produced significant improvements in the statistical results compared to the original edge-connectivity index, ε, for six of the seven properties studied. Some of the novel descriptors are able to describe physicochemical properties poorly correlated to the original ε index.