Comparison theorems on resistance distances and Kirchhoff indices of SS, TT-isomers

Comparison theorems on resistance distances and Kirchhoff indices of the so-calledSS- & TT-isomer graphs are established. Then these results are applied to compare Kirchhoff indices of hexagonal chains, showing that the straight chain is the unique chain with maximum Kirchhoff index, whereas the minimum Kirchhoff index is achieved only when the hexagonal chain is an “all-kink” chain.