Resonance Raman Spectroscopy of Manganese (III) Etioporphyrin I,Chromium (III) Tetraphenylporphin and Hemoglobin:The Dependence of Resonance Enhancement on the Resonant Electronic Transition.

摘要

Resonance Raman spectroscopy (RRS) and magnetic circular dichroism are used to study the electronic transitions of Mn (III) etioporphyrin I (MnETP). The data supports the assignment of the strong band of Mn (III) porphyrins between 460and 490nm to a charge transfer transition. The two bands occurring between 540and 600nm are assigned to vibronic components of a pi implies pi *transition. The band in the near uv appears to contain a number of components. It is suggested that this band has both pi implies pi *and charge transfer character. Dramatic differences are found in the RR spectra of MnETP upon excitation within different absorption bands. The RR spectra of MnETP - X (X = F exp - ,Cl exp - ,Br exp - , I exp - ,or butanol) excited in the charge transfer band show large differences in the low frequency region (100to 500cm exp -1 ),depending on the axial ligand. Pure Mn-halide vibrations are assigned. An explanation is proposed to account for the differences between the RR spectra excited in the Q bands and the charge transfer band. Some of the vibrational Raman bands in the low frequency region may serve as probes for the degree of out-of-plane distortion of the metal from the porphyrin plane. The resonance Raman spectra of Cr (III) tetraphenylporphin (CrTPP) indicate that the three absorption bands of CrTPP occurring between 420and 600nm result from pi implies pi *transitions. The resonance Raman spectra of F exp - , N exp -3and OH exp -complexes of methemoglobin are studied by excitation in the charge transfer bands,which occur between 590and 650nm. A selective enhancement of vibrations of the axial ligand against the iron is observed. The addition of inositol hexaphosphate results in no changes in the resonance Raman spectra. The lack of a shift in the energy of the Fe--F exp -vibration is interpreted to indicate that there is no movement of the iron relative to the porphyrin plane. (ERA citation 02:025142)