Ground States of Polyenes and Hunds Rule Violations

1 Ground States of Polyenes and Hund s Rule Violations 

A simple principle of the spin-Hamiltonian VB theory, first formulated by Ovchinnikov (13), applies to alternant conjugated molecules, that is, those molecules that possess fully spin-alternant determinants. The rule is stated as follows  

Ovchinnikov s Rule The lowest state of an alternant conjugated molecule will have the multiplicity associated with the Sz value of its MSAD, that is, it will be a singlet ifna = np in the MSAD, a doublet ifna = np + 1, a triplet ifna = np + 2, and so on. 

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