New topological indices with very high discriminatory power.

Several molecular descriptors are used in developing quantitative structure-activity relationships (QSARs). A large number of them are already in use and new descriptors are added every year. Two new topological indices with very high discriminatory power are reported in this paper. The two indices ranked all planar graphs of alkanes C(4) to C(6) uniquely and were found to have non-degenerate values for all the 7668 constitutional isomers (alkane trees) from C(4) to C(15). Low intercorrelation with several of the commonly used topological indices was studied using a diverse data set of 820 chemicals and the new indices proposed in the study were found to cluster in different nodes. This further confirmed their low intercorrelation with other molecular descriptors used in the study. The new descriptors were found to be useful in QSAR modelling.