Formula for calculating the Wiener polarity index with applications to benzenoid graphs and phenylenes

TL;DR

This paper presents a generalized formula for calculating the Wiener polarity index applicable to complex graphs, including those with cycles and shared edges, with applications to chemical graph theory.

Contribution

It extends previous formulas to include graphs with 4-cycles and shared edges, providing closed-form calculations for phenylenes and benzenoid graphs.

Findings

Derived a closed formula for phenylenes.

Recalculated Wiener polarity index for benzenoid graphs.

Characterized graphs with extremal Wiener polarity index values.

Abstract

The Wiener polarity index of a graph is defined as the number of unordered pairs of vertices at distance three. In recent years, this topological index was extensively studied since it has many known applications in chemistry and also in network theory. In this paper, we generalize the result of Behmaram, Yousefi-Azari, and Ashrafi proved in 2012 for calculating the Wiener polarity index of a graph. An important advantage of our generalization is that it can be used for graphs that contain $4$-cycles and also for graphs whose different cycles have more than one common edge. In addition, using the main result a closed formula for the Wiener polarity index is derived for phenylenes and recalculated for catacondensed benzenoid graphs. The catacondensed benzenoid graphs and phenylenes attaining the extremal values with respect to the Wiener polarity index are also characterized.