ESR and theoretical studies of trimer radical cations of coronene.

摘要: Abstract Highly resolved ESR spectra of monomer, dimer and trimer radical cations coronene (C24H12) were observed at room temperature for a solution 1,1,1,3,3,3-hexafluoro-2-propan-2-ol (HFP) containing thallium(III) trifluoroacetate as oxidant. The consisting multiple lines with isotropic 1H-hyperfine splitting (hfs) constants 0.0766 mT (24H) 0.013 mT (6H) attributable to mixture the cations, (C24H12)2+ (C24H12)3+. For (C24H12)2+, 1H-hfs constant agreed well reported value, 0.077 mT. However, (C24H12)3+, values significantly different from ones, 0.117 mT (12H) 0.020 mT (24H), by Ohya Nishiguchi et al. [H. Ohya-Nishiguchi, H. Ide, N. Hirota, Chem. Phys. Lett. 66 (1979) 581], but rather similar those Willigen van Willigen, E. De Boer, J.T. Cooper, W.F. Forbes, J. Chem . 49 (1968) 1190]. In conflict Willigen's report, however, no line broadening which has been ascribed low stationary concentration (C24H12)3+ was detected. Based on ab initio MO calculations benzene compact model C24H12, structure investigated in terms constants. A staggered sandwich C2v suggested being “global” minimum cation. structure, unpaired electron spin is predominantly localized central ring, qualitatively agreement previous results Ohya-Nishiguchi addition, “local” minimum, indicated have slipped Cs less stable ca. 19 kJ mol−1 than minimum. this nearly equally distributed both one two side C24H12 molecules. possibly cation analogous structure.