Electronic spectrum of cobalt-free corrins calculated by TDDFT method

The electronic spectra of protonated and unprotonated metal-free corrins were calculated by the TDDFT method in the B3LYP version. Two low energy forms were found from geometry optimization for the protonated corrin, as well as for the unprotonated one. The calculated energies of electronic transitions are in good agreement with the experimental spectrum of synthetic corrin. The largest difference is 0.45 eV and the average difference 0.25 eV. The spectrum of the unprotonated corrin is similar to the spectrum of the protonated corrin with more pronounced n --> pi* transitions due to one more lone electron pair on nitrogen atoms.