Multicenter bonds, bond valence and bond charge apportionment

In the same way that the valence of an atom issues from the definition of bond index? we show here that the three-center bond index lends itself to the definition of a bond valence. Within the charge of a bond, we show that its self-charge (i.e., the amount of electrons kept by the atoms involved in the bond) is split in such a way that the more electronegative atom tends to hold more electronic charge than the other atom. We give examples of these quantities and discuss the results for different kinds of chemical systems. We also give some results for four-center indices and report sis-center indices for hexagonal rings. (C) 1997 Elsevier Science B.V.