ON THE REVERSE SOMBOR COINDEX OF GRAPHS AND ITS CHEMICAL APPLICABILITY

Abstract

n this paper, we introduced a new parameter, known as reverse Sombor coindex. Also, we obgtained an exact expressions for the reverse Sombor index and reverse Sombor coindex for few standard graphs like paths, cycles, complete graphs, star graphs, wheel graphs, and complete bipartite graphs. Furthermore, several bounds are established with regard to classical graph parameters and wellknown topological descriptors such as the Zagreb indices and forgotten index. Bounds for these descriptors under Cartesian product and composition of graphs are also derived. In addition, the chemical applicability of revrese Sombor index and the reverse Sombor coindex are examined with the help of hetero-atom containing molecules and polycyclic aromatic hydrocarbons (PAHs) and are compared with Sombor index, first Zagreb index, and forgotten index.. The obtained correlation coefficients and coefficients of determination indicate strong linear relationships between the considered descriptors and total 𝜋-electron energy. In particular, the reverse Sombor coindex exhibited the highest predictive performance, yielding correlation coefficients of R=0.9921 for heteroatomcontaining molecules and R=0.9896 for polycyclic aromatic hydrocarbons (PAHs). These results demonstrate the usefulness of reverse degree-based descriptors in chemical graph theory, QSPR/QSAR studies, and molecular structure analysis.