Biradicaloid heterosymmetric

Heterosymmetric Biradicaloids The Hamiltonian matrix has the following form ... 

It is interesting to distinguish three cases (1) strong heterosymmetric biradicaloid SAB > 8C, (2) weak heterosymmetric biradicaloid SAB < Sc, and (3) critical heterosymmetric biradicaloid 5AB = Sc. 

V. Bonacic-Koutecky, K. Schoffel, and J. Michl, Theor. Chim. Acta, 72,459 (1987). Critically Heterosymmetric Biradicaloid Geometries of Protonated Schiff Bases—Possible Consequences for Photochemistry and Photobiology. 

Figure 4.20. The two-electron two-orbital model a) for a homosymmetric biradicaloid and b) for a heterosymmetric biradicaloid schematic representation of state energies, relative to the T state, as a function of the interaction integral y or as a function of the electronegativity difference 6 of the orbitals x and Xt (by permission from Michl and Bona i(5-Koutecky. 1990).

Figure 4.23. Schematic representation of the state energies of a dissociating n bond as an example of a heterosymmetric biradicaloid. Shown are the S S, and T, energies as a function of the twist angle 6 and the electronegativity difference 6 of orbitals Xa and Xb (t>y permission from BonaCid-Kouteck and Michl, 1985b).

First of all, we consider the significance of the presence of C-, +, the coefficient of the in-phase combination of the two hole-pair functions in the So wave function, in Equation 4.12. In the simple model for a perfect biradical, this in-phase combination is exactly equal to the wave function of the Sj state, and it does not enter into those of the So and S, states at all. Thus, in this approximation. So does not spin-orbit couple to the triplet. The same is true in weakly heterosymmetric biradicaloids (0 < 5 < S ), in which the in-phase hole-pair character is shared by S, and Sj, but not Sg, and the former two spin-orbit couple to T, but So does not. In strongly heterosymmetric... 

The global term pericyclic funnel will be used to refer to the funnel or funnels in the S surface that occur at the critically heterosymmetric biradicaloid geometries reached near the halfway point along the path of a thermally forbidden pericyclic reaction, and the minima in S, that are encountered along one-dimensional cuts along reaction paths that miss the conical intersections (in particular, those along high-symmetry paths, which pass... 

As a result of the rectangular geometry, the pericyclic minimum at the head-to-tail dimerization path, which corresponds to a 1,3-disubstituted heterosymmetric biradicaloid, is likely to be deeper than that at the head-... 

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