ELECTRONIC RAMAN-SPECTRA OF A LOW-SPIN FE-III PORPHYRIN AND REEXAMINATION OF THE VIBRATIONAL-SPECTRA OF K-3[FE(CN)(6)] AND [FE(C5H5)(2)]BF4

The resonance Raman spectra of ((n)Bu(4)N)[Fe(CN)(2)TPP] (((n)Bu(4)N): tetra(n-butyl)ammonium; TPP:m-tetraphenylporphyrin), K-3[Fe(CN)(6)] a nd [Fe(C5H5)(2)]BF4 have been investigated. A molecular electronic Ram an (ER) effect at 545 cm(-1) is observed for ((n)Bu(4)N)[Fe(CN)(2)TPP] . The transition occurs between lower ''Gamma(7)'' and upper ''Gamma(8 )'' level of the spin-orbit split ground state assuming pseudo-octahed ral symmetry. In contrast to earlier studies no ER effect is detected for K-3[Fe(CN)(6)] and [Fe(C5H5)(2)]BF4. For Raman shifts < 800 cm(-1) only one strong Raman line is observed for [Fe(C5H5)(2)]BF4 at 311 cm (-1), assigned to the iron ring stretch designated by nu(4) (a(1g) in D-5d). Due to a phase transition of K-3[Fe(CN)(6)], two additional str ong vibrational lines at 329 and 352 cm(-1) appear in the Raman spectr um taken at 10 K. Their intensities show A ''term'' behaviour of the r esonance Raman effect with overtones and combinations for both lines. These are components of the vibronic combinations with the nu(6), nu(7 ), and nu(8) modes (t(1u) in O-h) in the IR spectra, too.