The molecular topological index is a graph index defined by MTI = sum_(i = 1)^n E_i, where E_i are the components of the vector E = (A + D) d, with A the adjacency matrix, D the graph distance matrix, and d the vector of vertex degrees of a graph. The molecular topological index is well-defined only for connected graphs, being indeterminate for disconnected graphs having isolated nodes and infinity for all other disconnected graphs.