Effects of Substituents and Solvents on the Electronic Spectra of 9,10-Dihydro-9,10-o-benzenoanthracene-1,4-diones: Intramolecular Charge Transfer

Article abstract of DOI:10.1246/bcsj.62.800

Electronic spectra of substituted 9,10-dihydro-9,10-o-benzenoanthracene-1,4-diones (triptycenequinones) in various solvents and that of benzo- and dibenzotriptycenequinones were investigated in this paper.Intramolecular charge-transfer (CT) bands were observed in triptycenequinone system as a result of intramolecular interaction between benzene ring and benzoquinone moiety.Substituents on the benzene rings strongly affected the CT bands.Electron-donating groups gave absorption maxima at long wavelength.Naphthalene ring gave similar but stronger CT bands than benzene ring.Hammett ?⁺ value of substituents gave good linear relationship with the energy of the CT bands.Calculations of reduced charge matrix of triptycenequinones by extended Hueckel theory showed the charge of aromatic ring(s) were transferred to benzoquinone moiety accompanying HOMO-LUMO excitation.Especially, absorption maxima of the methyl-substituted triptycenequinones gave good correlation with the amounts of charge transferred from benzene ring to benzoquinone moiety.These analysis confirmed clearly CT character of the absorption maxima of triptycenequinones.However, solvent effect of these CT bands maxima is not so clear as the substituent effect.