Effects of solvents, axial ligation, and radical cation formation on the V=O stretching Raman frequency in vanadyl porphyrins: implications for peroxidase intermediates

Journal Article · Wed Jun 22 04:00:00 EDT 1988 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00221a009· OSTI ID:6254599

Su, Y O; Czernuszewicz, R S; Miller, L A; Spiro, T G

The systematics of the V/double bond/O stretching frequency in vanadyl porphyrins are investigated with resonance Raman (RR) spectroscopy. For a series of solvents the frequency decreases with increasing solvent acceptor number consistent with solvent-induced polarization of the V-O bond. Variations in the solvent dependence are seen for different porphyrins, reflecting different polarization effects on the peripheral substituents. In coordinating solvents a second V-O stretching band, at lower frequency, arises from six-coordinate species. The downshift in v/sub V-O/ upon ligation increases with increasing donor strength of the ligand. It is larger for imidazolate than imidazole, and it is especially large for hydroxide; the hydroxide effect is attributed to OH/sup -/ ..-->.. V/sup IV/ ..pi..-donation, competing with the oxo ligand for acceptor d orbitals. The RR spectrum of (VO)OEP/sup center dot +/ produced by electrochemical oxidation shows porphyrin skeletal mode frequency shifts similar to those seen for other OEP ..pi..-cation radicals. The V-O stretching frequency increases 15 cm/sup -1/ relative to (VO)OEP. These findings are discussed in relation to recent RR data on ferryl porphyrins and ferryl species in home proteins. Differences among these species can be accounted for on the basis of proximal and distal effects.

• Research Organization: Princeton Univ., NJ (USA)
• DOE Contract Number: AC02-81ER10861
• OSTI ID: 6254599
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 110:13; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400400 -- Electrochemistry
CARBOXYLIC ACIDS
CATIONS
CHARGED PARTICLES
CHEMICAL BONDS
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
DATA
ELECTROCHEMISTRY
ELEMENTS
ENZYMES
EXPERIMENTAL DATA
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROGEN
HYDROGEN COMPOUNDS
INFORMATION
IONS
LASER SPECTROSCOPY
LIGANDS
NONMETALS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SOLVENTS
OXIDATION
OXIDOREDUCTASES
OXYGEN
OXYGEN COMPOUNDS
PEROXIDASES
PORPHYRINS
RADICALS
RAMAN SPECTRA
RAMAN SPECTROSCOPY
REACTION INTERMEDIATES
SOLVENT PROPERTIES
SOLVENTS
SPECTRA
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES
VANADIUM COMPLEXES
WATER