The total n-electron energy of phenylenes is approximated by means of a linear combination of the fi rst few spectral moments of both molecular and line graphs. The two sets of moments produce very similar results, with very high accuracy. It is found that over 99.8% of the HMO totaln-electron energy of phenylenes is determined by the number of carbon atoms. Number of bay regions plays a signif...

1031 Vertex-degree-based molecular structure descriptors of benzenoid systems and phenylenes IVAN GUTMAN* and BORIS FURTULA** Faculty of Science, University of Kragujevac, P. O. Box 60, 34000 Kragujevac, Serbia (Received 12 December 2011) Abstract. Several recently published papers report expressions for various vertex-degree-based molecular structure descriptors of benzenoid systems and phenyl...

In a series of publications Estrada (Estrada, E. J. Chem. Inf. Comput. Sci. 1996, 36, 844-849; 1997 37, 320-328; 1998, 38, 23-27) employed spectral moments of line graphs in QSPR and QSAR relationship studies of various classes of compounds. A recent paper (Marković, S.; Gutman, I. J. Chem. Inf Comput. Sci. 1999, 39, 289-293) reported that in QSPR and QSAR investigations of benzenoid hydrocarbo...

the sadhana index (sd) is a newly introduced cyclic index. efficient formulae for calculatingthe sd (sadhana) index of linear phenylenes are given and a simple relation is establishedbetween the sd index of phenylenes and of the corresponding hexagonal sequences.

The hyper-Wiener index WW of a graph G is defined as WW(G) = (summation operator d (u, v)(2) + summation operator d (u, v))/2, where d (u, v) denotes the distance between the vertices u and v in the graph G and the summations run over all (unordered) pairs of vertices of G. We consider three different methods for calculating the hyper-Wiener index of molecular graphs: the cut method, the method...

Our investigations are motivated by recent papers concerning the spectral moments of the edge-adjacency matrix, which were successfully employed in QSAR and QSPR studies of different classes of compounds [Estrada, E. J. Chem. Inf. Comput. Sci. 1996, 36, 844-849; 1997, 37, 320-328; 1998, 38, 23-27]. In this work, the evaluation of the 10th spectral moment of the vertex-adjacency matrix for pheny...

The Sadhana index (Sd) is a newly introduced cyclic index. Efficient formulae for calculating the Sd (Sadhana) index of linear phenylenes are given and a simple relation is established between the Sd index of phenylenes and of the corresponding hexagonal sequences.