The Improred Valence Connectivity Topological Index and Its Application δ_i^- Comparison with δ_v in QSAR/QSPR of Three Systems

The valence connection index δ_v is not suitable for the inorganic compounds which have complicated oxidation state （for example,Si⁺,Si²⁺, Si³⁺, Si⁴⁺ ） and the organic compounds which include many sorts of heteroatoms such as F,Cl,Br,I,O,S,etc.,in order to enlarge the field of δ_v, on the basis of δ_v, we defined the valence connection index δ_i^- by introducing the main quantum number,the number of valence electrons to the atom under study.The improved molecular topological index ¹X^- was defined by means of δ_i^- .The X₀^- of SiX_n（n =1~4,X=F,Cl,Br,I）,the ¹X^- of Cl_mSi（OR）_n（m+n =4） and halogeno-benzene were calculated.The linear relations of X₀^- and the Δ_fH_m of SIX_n, ¹X^- and the GC retention index （RI） of ClmSi（OR）_n, ¹X^- and the solubility S and the distribution coefficient P （octanol/water） of halogeno-benzene are good,their correlation coeficients R are 0.9928,0.97,0.9694,0.9929,respectively.The results are much better than those of the topological indicex X₀^v and X^v which are formed by δ_v （the correlation coefficients are 0.8862,0.70,0.9131,0.9387,correspondingly）.