High‐frequency vibrational mode characterization of Zn(II), Ni(II) and Co(II) tetraphenylchlorins

The detailed resonance Raman spectra of metallotetraphenylchlorins with B, Q_x and Q_y excitations and excitation profiles of Raman modes on the Q_y absorption band have been reported. In metallotetraphenylchlorins, the character of the vibrational eigenvector and the localization of the modes in the pyrrole rings raised by the symmetry are different from those of metallooctaethychlorins. A recent normal mode calculation on Cu(II) tetraphenlchlorin based on the semi‐empirical quantam chemistry force field (QCFF/PI) method was utilized to elucidate the vibrational mode assignment of Zn(II), Ni(II) and Co(II) tetraphenylchlorins. For Raman excitation profiles on Q_y(O, O) and Q_y(O, 1) absorption bands, it is observed that some polarized Raman bands have contributions not only from A‐term scattering but from Herzberg‐Teller scattering. This can be explained by the symmetry lowering and the localized normal mode character of metallotetraphenylchlorins. For depolarized and anomalously polarized Raman bands, the vibronic coupling (interstate mixing) is strongly introduced.