Structure of the lowest triplet states of poly-α-methylstyryl sodium. Ab initio calculations

Article abstract of DOI:10.1007/BF02683917

Ab initio optimization of a poly-α-methylstyryl sodium (PMSNa) fragment consisting of two cis units yields a triplet state energy which is close to the ground state energy. A new mechanism is proposed for depolymerization of living polymers, which implies that an elementary step involves excitation to the low-lying triplet state with a charge transfer and with further bond cleavage. In the reaction structure, electronic excitation occurs with a minor (～0.5 A) displacement of the Na⁺ cation between the last and the last but one monomer units. The reversible polymerization/depolymerization reaction of PMSNa in THF was studied experimentally. The experimental (5.6 kcal/mole) and calculated (7.3 kcal/mole) polymerization enthalpies are in reasonable agreement.