Molecular connectivity indices of iterated line graphs. A new source of descriptors for QSPR and QSAR studies

Connectivity indices chi of the line graph L and higher line graphs L-n, n = 2, 3, ..., of the molecular graph G are examined as possible structure-descriptors in QSPR and QSAR studies. In the case of alkanes, regression models based on chi(G), chi(L), chi(L-2), chi(L-3) and chi(L-4) are found to be significantly better than those based solely on the index chi(G), with chi(G) continuing to play an important role. This has been demonstrated for boiling point, molar volume, molar refraction and surface tension. The same model was then applied for predicting the microsomal p-hydroxylation of aniline by alcohols. The QSAR model obtained by using connectivity indices of higher line graphs represents a significant improvement respect to the model using solely chi(G).