The multiconfiguration Spin-Coupled approach for the description of the three-center two-electron chemical bond of some carbenium and nonclassical ions

Three-centre two-electron bonds from the quantum interference perspective

“…The molecular geometry was optimized in all cases, considering D 3h symmetry. At the GVB-PP level two different states were found, as predicted by Barbosa and co-workers, 50 which correspond to the resonance hybrids. The electric dipole moment calculated at the center of mass for each state shows that the electrical charge is not symmetrically distributed and, therefore, that the states are not adequate to individually describe H 3 + .…”

“…At this point it would be instructive to compare the SC(2,3) description of 3c2e bonds with the one of the MC-SC approach proposed by Barbosa and co-workers. 50 In the cited paper, the authors reported results for the allyl and 2-norbornyl cations using the same basis sets used in the present work. In order to match the methodology adopted by Barbosa and co-workers, the SC(2,3) calculations presented in this section have been completely remade.…”

“…The reader is encouraged to address a previous article 9 for a brief history of the theoretical treatment of 3c2e bonds, especially in terms of the 'classical' and modern valence bond approaches. The recent work of Barbosa et al 50 is really worth mentioning, where it is shown that a multiconfigurational approach is required in order to correctly describe 3c2e bonds. They have proposed a spin-coupled multiconfigurational (MC-SC) wave function, which considers a combination of a number of different structures treated under the framework of the spin coupled generalized valence bond (SCGVB) theory.…”