NH-tautomerism and visible absorption spectra of porphyrins with nonsymmetrical substitution: oscillator model and mo calculations

Abstract

On the basis or experiments Ihe oscillator model has been established for individual NH tautomers or porphyrins with asymmetrical substitution. CNDO/2 calculations explain the inversion of Q ₓ (O.O) and Q y (O.O) electronic transition intensities in NH tautomers as a consequence of the inversion of LUMO coefficients c₁ and c₂ for fixed x and y molecular oscillators