Electronic Raman Spectra of a Low-Spin Fe~Ⅲ Porphyrin and Reexamination of the Vibrational Spectra of K_3[Fe(CN)_6] and [Fe(C_5H_5)_2]BF_4

摘要

The resonance Raman spectra of (~nBu_4N)[Fe(CN)_2TPP] ((~nBu_4N): tetra(n-butyl)ammonium; TPP: m-tetraphenylporphyrin), K_3 [Fe(CN)_6] and [Fe(C_5H_5)_2]BF_4 have been investigated. A molecular electronic Raman (ER) effect at 545 cm~(-1) is observed for (~nBu_4N)[Fe(CN)_2TPP]. The transition occurs between lower 'Γ_7' and upper 'Γ_8' level of the spin-orbit split ground state assuming pseudo-octahedral symmetry. In contrast to earlier studies no ER effect is detected for K_3 [Fe(CN)_6] and [Fe(C_5H_5)_2]BF_4. For Raman shifts < 800 cm~(-1) only one strong Raman line is observed for [Fe(C_5H_5)_2]BF_4 at 311 cm~(-1), assigned to the iron ring stretch designated by υ_4 (a_(1g) in D_(5d)). Due to a phase transition of K_3[Fe(CN)_6], two additional strong vibrational lines at 329 and 352 cm~(-1) appear in the Raman spectrum taken at 10 K. Their intensities show A "term" behaviour of the resonance Raman effect with overtones and combinations for both lines. These are components of the vibronic combinations with the υ_6, υ_7, and υ_8 modes (t_(1u) in O_h) in the IR spectra, too.