The use of subgraphs in QSPR/QSAP semi-empirical models of chemical properties and biological activities is discussed beginning with the grounding works of Smolenski, Gordon, Kier and other pioneers of chemical graph theory. The more complete representation of molecular structure by the concept of overall topological descriptors is analyzed in detail. It is shown that the resulted better prediction of physico-chemical properties follows from capturing patterns of increasing complexity of molecular structure, such as increasing branching, cyclicity, and centrality of molecular skeleton. The pattern of decreasing the overall distance in polymeric structures and crystal clusters is also shown to correlate with their properties, respectively stability. Included here are the first equations relating directly a topological descriptor (the Wiener number of a graph) to the radius of gyration and viscosity of acyclic polymers.
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