Biradicaloids Hamiltonian matrix

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

Homosymmetric Biradicaloids The Hamiltonian matrix for the singlet state is... 

So far, the preceding considerations have been very useful for characterization of states and for ordering of singlet-state energies relative to (T) with fixed values of K and K. Nevertheless, we could not receive any qualitative ideas about the shapes of energy surfaces as the biradicaloids develop from the normal molecules. For this purpose the introduction of overlap, which we have neglected so far, is necessary. The Hamiltonian matrix for nonorthogonal orbitals A and B for nonsymmetric biradicaloid is... 

Simultaneous presence of covalent and polarizing perturbations (tab AB ( ) leads to non-symmetric biradicaloids. Their general features again follow from a consideration of the Hamiltonian matrix in Table 5. For instance, they permit a ready rationalization of the preference of donor-acceptor pair molecules such as NH2-BH2 for planarity in the lowest singlet state Sq and orthogonality in the first excited singlet state Si [1,6]. 

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See also in sourсe #XX -- [ ]

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