Novel topological index for research on structure-property relationships of complex organic compounds.

Based on bonding parameters such as Yang's Electronegative Force Gauge Y(i), electronic number of valence layer Z(i), number of combined hydrogen atoms hi, number of bonding electron b(i), and quantum number such as the highest main quantum number of valence layer n(i), a novel atomic valence delta(i)(Y) is defined and a novel topological index (1)X(Y) is derived from the atomic valence. The atomic valence is defined as delta(i)(Y) = (Z(i) - h(i))b(i)/n(i)(2)Y(i), while the topological index is expressed as (1)X(Y) Sigma(i,j=1)(m) (delta(i)(Y)delta(j)(Y))(-1/2). Subsequently, the index (1)X(Y) is utilized to study the structure-property relationships of complex organic compounds. The results of correlativity showed that the index is highly and extensively correlated with such properties as solubility of phenyl chlorides, gas chromatographic retention index of alkoxyl silanes, and toxicity of heterocyclic nitrogen-containing compounds. Moreover, predicted values are quite consistent with experimental ones when the index is employed to predict the partition coefficient (log P) of fatty alcohols, phenyl chlorides, and barbitals. Compared to the topological indices reported in the literature, the universality and reliability of (1)X(Y) to the properties of complex organic compounds have been distinctively improved, and its calculating process is simple and convenient. (C) 2003 Wiley Periodicals, Inc.