IDENTIFICATION OF THE S-4(-) RADICAL-ANION IN SOLUTION

Solutions of lithium polysulfide (Li2Sn) in DMF have been investigated by ESR spectroscopy, The numerical analysis of the data shows that fo r 1 < n less than or equal to 6, the experimental signal is accurately described by a single Lorentzian lineshape, while two Lorentzian comp onents are required for n > 6. The variation of the concentration of e ach signal is determined versus n, The signal observed for all values of n must be assigned to S-3(-), while the signal observed only for n > 6 must be assigned to S-4(-), resulting from the dissociation of S-8 (2-). This is the first identification of S-4(-) in solution. This stu dy shows that the concentration of S-4(-) is very low in these solutio ns. The ESR signal of S-4(-) has been characterized and the value of t he equilibrium dissociation constant of S-8(2-) has been estimated at 10(-9) M.