Modern valence-bond-like representations of selected D6h "aromatic" rings.
Starting from CASSCF(6,6)/6-31G(d,p) wave functions, we consider different valence-bond (VB)-like interpretations of the pi electron systems for various (constrained) "benzene-like" D(6)(h)() rings, exploiting the invariance of the total wave function to arbitrary nonsingular transformations of the active orbitals. Quantities obtained rather directly from the various calculations provide a fairly consistent ordering of the degree of aromaticity: C(6)H(6) approximately B(6) > N(6) > Al(6) approximately Si(6)H(6) > P(6). Representations based on mutually orthogonal orbitals are found to be somewhat less satisfactory than those that have no such constraints on the overlaps between the active orbitals.
Hill
J Grant
JG
Department of Chemistry, University of York, Heslington, UK.
Cooper
David L
DL
Karadakov
Peter B
PB