Bond orbitals from chemical valence theory.

Two sets of orbitals are derived, directly connected to the Nalewajski-Mrozek valence and bond-multiplicity indices: Localized Orbitals from the Bond-Multiplicity Operator (LOBO) and the Natural Orbitals for Chemical Valence (NOCV). LOBO are defined as the eigenvectors of the bond-multiplicity operator. The expectation value of this operator is the corresponding bond index. Thus, the approach presented here allows for a discussion of localized orbitals and bond multiplicity within one common framework of chemical valence theory. Another set of orbitals discussed in the present work, NOCV, are defined as eigenvectors of the overall chemical valence operator. This set of orbitals can be especially useful for a description of bonding in transition metal complexes, as it allows for separation of the deformation density contributions originating from the ligand --> metal donation and metal --> ligand back-donation.