Resonance Raman scattering from metalloporphyrins. Metal and ligand dependence of the vibrational frequencies of octaethylporphyrins

Abstract

Resonance Raman spectra of various metallo-octaethylporphyrins [M(OEP)] were measured and the observed metal-ligand dependence of Raman frequencies was interpreted satisfactorily in terms of the conjugation interaction between the metal 4p2 orbital and the porphyrin a2U orbital. A method was developed for distinguishing the Big modes from the B2g modes of M(OEP) on the basis of group theoretical considerations. Inverse polarization occurs generally for symmetric M(OEP) complexes while only anomalous polarization occurs for the less symmetric OEPH2 and metallo-protoporphyrin complexes. Analysis of the intensity profiles of Raman lines suggests that the intermediate electronic state involved in the Raman scattering of Fe(OEP)Cl is related to the absorption band at 535 nm.

Resonance raman studies of a c type algal cytochrome deuterium shifts and a comparison with mammalian cytochrome c

“…The magnitude of shifts in different regions do vary as expected: in the 1300-1700 cm -1 region they are small and usually less than 20 cm-L The resonance Raman spectra of normal metalloporphyrins and their meso-deuterated derivatives exhibit similar shifts in this frequency range [13,15,16] and it appears likely that the deuterium shifts of the heme c in algal cytochrome in this region demonstrate only a small amount of mixing of the methine bridge CH deformation or perhaps CH stretching with the porphyrin macrocycle stretching modes (as suggested by Kitagawa et al [15].…”

Vibrational and electronic spectra of new liposoluble metalloporphyrins in a nonpolar noncoordinating solvent

“…Similar relationships are observed between spectral shifts of ir bands and the following structural parameters: (a) the strength of the N-metal bond (13,14); (b) the number of d electrons on the metal (16); (c) the center-to-nitrogen distance or core size (7,35,(39)(40)(41); (d) the stability of the complexes (38); (e) the spectral shifts in the UV-vis region (7,12,42). The correlation factors between the ir displacement and the parameters mentioned are seldom greater than 0.9 even when the series of complexes are restricted to the ones formed with the elements of one single group or with the elements of a period in the periodic table.…”

Resonance Raman spectra of methemoglobin derivatives. Selective enhancement of axial ligand vibrations and lack of an effect of inositol hexaphosphate

“…Resonance Raman spectroscopy can serve as a structural probe for biological nolecules such as herogloo±n and myoglooin (Spiro, 1975 cmd ref-• exenc:es therein;Yamanoto, et al, 1973;Kitagawa et al, 1975;Ozaki, et al, ' ' 1976). Upon excitation within the absorption bands of the here c:hra;ophore a selective enhanc:errent oa:urs in the intensity of the Ram:m peaks resulting fran bene vibra~ons (Spiro, 1975) •.…”

“…Since an inequivalency of the x andy directions occurs at 6250 R, a des-:eription of the electronic transitions in the D2h point group is appropriate. In the o 211 point group the syrcrretry of the vibrations which would mix x andy electronic transitions is: (Kitagawa, et al, 1975), pression (Albrecht, 1961;Asher and Sauer, 1976). Thus, the inequivalency in the x and y directions may result fran an interaction not through the iron but directly on the porphyrin plane by the hane environmant.…”