FTIR spectra and normal-mode analysis of chlorin e(6) and its degradation-induced impurities.

Fourier transform infrared spectra of chlorin e(6) and its trisodium salt are presented. The geometrical structure and frequencies of normal vibrations of both compounds were calculated using density functional method with the PBE exchange-correlation functional. The frequencies were assigned and IR spectra of the studied molecules were interpreted for the first time. Spectral effects of degradation of chlorin e(6) and its trisodium salt upon their storage on the air are analyzed. The possible structures of degraded species are discussed.