Aromatic Nucleophilic Substitution. 21. Electronic Structures of 1,3-Dinitro-4-phenanthryl Methyl Ether and the 4,4-Disubstituted 1,3-Dinitrophenanthrene Meisenheimer Complex

Article abstract of DOI:10.1021/jo00225a024

The electronic structures of 1,3-dinitro-4-phenanthryl methyl ether (2) and its 4,4-dimethoxy-1,3-dinitrophenanthrene Meisenheimer complex (3), formed from 2 and NaOCH3, were studied by UV-visible and NMR spectra and compared with the results calculated by a semiempirical Pariser-Parr-Pople method.The electronic transitions in the ether 2 and complex 3 were assigned to ^*? <*> ?.Calculated transition energies and oscillator strengths agree well with the observed values.Calculations showed that in the S₀ state of complex 3 90.3percent of one negative charge donated by ^-OCH3 is distributed on the 1- and 3-NO2 groups and that in the S₁ <*> S₀ transition of the complex the ? formal charge is further spread over the 1- and 3-NO2 groups.A kinetic measurement in CH3OH at 25 deg C gave a little smaller equilibrium constant for formation of 3 than that for the similar naphthalene anionic ? complex.