A. Toropov et al., 3D WEIGHTING OF MOLECULAR DESCRIPTORS FOR QSPR QSAR BY THE METHOD OF IDEAL SYMMETRY (MIS) - 1 - APPLICATION TO BOILING POINTS OF ALKANES/, Journal of molecular structure. Theochem, 424(3), 1998, pp. 237-247
The method of ideal symmetry (MIS), developed recently, presents molec
ules as systems of mutually repulsing atoms connected by covalent bond
s of constant length. In this paper we have used MIS optimized geometr
y to define a vertex 3D weight as a metric analogue of the vertex dist
ance sum in molecular graphs. These 3D weights were used as a substitu
te for the vertex degrees in several well known topological (2D) indic
es, thus producing a series of 3D-weighted molecular descriptors. The
novel indices were tested in calculating the boiling points of a serie
s of 73 C3-C9 alkanes and showed generally a better performance than t
he original 2D indices. The best 1-, 2-, and 3-variable linear regress
ion models incorporated 3D zero-order molecular connectivity with corr
elation coefficients of 0.9892, 0.9961, and 0.9986, and standard devia
tions of 5.97, 3.64, and 2.17 degrees C, respectively. The approach wa
s further validated by correlations with four other properties of alka
nes (heats of formation, heats of vaporization, heats of atomization,
and molar volume). The potential of the proposed 3D weighting of topol
ogical indices for QSPR/QSAR studies was thus demonstrated. (C) 1998 E
lsevier Science B.V.