The eccentric connectivity index of nanotubes and nanotori

Let GG be a molecular graph. The eccentric connectivity index ξc(G)ξc(G) is defined as ξc(G)=∑u∈V(G)degG(u)εG(u)ξc(G)=∑u∈V(G)degG(u)εG(u), where degG(u)degG(u) denotes the degree of vertex uu and εG(u)εG(u) is the largest distance between uu and any other vertex vv of GG. In this paper exact formulas for the eccentric connectivity index of TUC4C8(S)TUC4C8(S) nanotube and TC4C8(S)TC4C8(S) nanotorus are given.