Zur Chemie von Pyrrolpigmenten, 55. Mitt.

2,3-Dihydrobilatrienes-abc substituted with carboxy and amino residue bearing groups in 3- and 12-positions have been prepared. Spectrophotometric titrations of these derivatives revealed that the influence of a non-conjugated positive or negative charge in the vicinity of the chromophore has only marginal influence on the absorption spectra. Rather small hypsochromic and bathochromic shifts of the long wavelength absorption band were observed and are discussed with respect to their origin. The results indicate that the influence of non-conjugated charges is not a main reason for spectral shifts accompanying photochemical and thermal transformations of the phytochrome chromophore.