THE ELECTROTOPOLOGICAL STATE - STRUCTURE INFORMATION AT THE ATOMIC LEVEL FOR MOLECULAR GRAPHS

The electrotopological state, a novel representation of atoms in molecules, is developed from chemical graph theory as an index of the graph vertex (or skeletal group). This new index combines both the electronic character and the topological environment of each skeletal atom in a molecule. The electrotopological state (E-state) of a skeletal atom is formulated as an intrinsic value I(i) plus a perturbation term, DELATA-I(i), arising from the electronic interaction and modified by the molecular topological environment of each atom in the molecule. The atom intrinsic value, for first-row atoms, is given as I = (delta-v + 1)/delta, in which delta-v and delta are the counts of valence and sigma electrons, respectively, for the atom in the molecular skeleton. The E-state, S(i), for atom i is defined as S(i) = I(i) + DELTA-I(i), where the influence of other atoms on atom i, DELTA-I(i), is given as SIGMA(I(i) - I(j))/r(ij)2; r(ij) is the graph separation between atoms i and j, counted as the number of atoms inclusive of i and j. Information in the electrotopological state is revealed by examples of various types of organic structures, including skeletal branching and heteroatom variation. Applications of this new method are given for O-17 NMR chemical shift and inhibition of flu virus.