Sulfur-centered radicals from mono- and polythia compounds

1 Sulfur-centered radicals from mono- and polythia compounds 

The basic feature of the sulfiir-sulfur bond in the dimer radical cation (R2S)2 introduced above is that it contains three electrons, namely, two bonding a-electrons and one antibonding a -electron. Formally, it can be viewed as resulting from an interaction of a singly occupied p-orbital of the sulfur-centered radical cation, R2S , and the p-lone pair of a second non-oxidized sulfur.56.85 jg depicted in eq. 40a and associated orbital 

This is, in fact, the rationale behind the above formulated equilibrium between the three-electron bonded species and its conjugate monomeric radical cation. The notation for this type of bond, incidentally, has been introduced by us and is now generally accepted and widely used. 

The probably most informative property of the 2a/la three-electron bonded species is their optical absorption. Structureless bands peaking in the visible exhibit extinction coefficients of = 6 ( 1) x 1Q3 cm-i and are characterized by a considerable broadness (= 1.0 0.2 eV) indicating that the transition is an allowed one.71 83 

The actual transition occurs between the uppermost doubly occupied orbital. 

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