Complexity of molecules

Several currently used measures of the complexity of molecules, such as, for example, those by Bertz and Randic or those based on the number of spanning trees, are briefly reviewed. We also proposed as complexity measures the sum of vertex-weights and the sum of edge-weights and their variants related to partition of vertex-weights and edge-weights into classes by their numerical values. The vertex-weights considered are the squares of the vertex-degrees, and the edge-weights are products of vertex-degrees making up the edges. Comparison is made between considered complexity measures for selected molecular graphs. All considered indices increase with increasing size and cyclicity and most with increasing branching. However, they differ regarding the influence of symmetry.