Resonance Raman vibrational analysis of Cu sup II , Fe sup III , and Co sup III porphyrin. pi. cation radicals and their meso-deuteriated analogues

Journal Article · Thu Feb 23 00:00:00 EST 1989 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100341a028· OSTI ID:5112543

Oertling, W A; Salehi, A; Chang, C K; Babcock, G T ^[1]

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1. Michigan State Univ., East Lansing (USA)

Analysis of the near-UV resonance Raman enhanced vibrations in the 1000-1700-cm{sup {minus}1} range of Cu{sup II}, Fe{sup III}, and Co{sup III} complexes of octaethylporphyrin and etioporphyrin I {pi} cation radicals and of the corresponding complexes with {sup 2}H substituted at the porphyrin methine carbon positions is presented. Comparison of analogous spectra of octaethylporphyrin vs etioporphyrin I complexes is used to identify vibrations involving the pyrrole b-carbon atoms and thus serves as an alternative to isotopic labeling at this position. The results are consistent with and provide an extension of our earlier vibrational assignments, which were based on structural trends and depolarization ratios of the Raman bands in the 1450-1700-cm{sup {minus}1} region. Our results reveal that the wavenumbers of the octaethylporphyrin C{sub a}C{sub m}, C{sub a}N, and C{sub a}C{sub b} internal stretching coordinates decrease slightly while those of the C{sub b}C{sub b} stretching coordinates increase when the macrocycle is oxidized by one electron. The magnitude of the wavenumber shifts caused by methine carbon deuteriation and b-carbon substitution are comparable for the neutral and {pi} cation species. This suggests that although the force constants are changed ({approx}1-3%) upon oxidation, the overall potential energy distributions of the normal coordinates of the {pi} cation radical remain similar to those of the parent compounds, most likely reflecting similar macrocycle stereochemistry for neutral and oxidized species in CH{sub 2}Cl{sub 2} solution. Our analysis suggests that the optical and resonance Raman spectral properties of these complexes strongly reflect the conformation of the oxidized porphyrin ring. This implies that the distinct optical spectra of the cobaltic octaethylporphyrin {pi} cations.

• OSTI ID: 5112543
• Journal Information: Journal of Physical Chemistry; (USA), Vol. 93:4; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
14 SOLAR ENERGY
COBALT COMPLEXES
VIBRATIONAL STATES
COPPER COMPLEXES
DEUTERIUM COMPOUNDS
IRON COMPLEXES
PORPHYRINS
CATIONS
EXPERIMENTAL DATA
ISOTOPE EFFECTS
NORMAL-MODE ANALYSIS
RADICALS
RAMAN SPECTROSCOPY
RESONANCE SCATTERING
SPECTRAL SHIFT
CARBOXYLIC ACIDS
CHARGED PARTICLES
COMPLEXES
DATA
ENERGY LEVELS
EXCITED STATES
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
INELASTIC SCATTERING
INFORMATION
IONS
LASER SPECTROSCOPY
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
SCATTERING
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties
140505 - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)