Quantum-chemical study of the activity of styrene polymerization intermediates during the electrochemical generation of 9-fluorenone radical anions

The electronic structure and geometry of R.- Mt(n+) ion pairs formed during the electrochemically initiated styrene polymerization in the 9-fluorenone (R)-monomer-DMF-metal (Mt(n+) = Li+, Na+, K+, Ca2+) perchlorate systems is studied by the CNDO/2 method. A nonplanar configuration is typical for R.-Li+ and R.- Na+ (Mt(+) is located above O atom on the perpendicular to the R plane), while R.- K+ and R.-Ca2+ are planar. The spin density is localized at the metal atom in R.-Ca2+ and is significantly redistributed toward the oxygen atom in R(.-)Mt(+). This correlates with the ability of ion pairs to form dimers as confirmed by the data of voltammetry, EPR, and UV spectroscopy. The results obtained suggest that the electrochemical initiation of polymerization is realized by the transfer of two electrons from the dimeric associate to the styrene molecule.