Resonance Raman spectra of chlorin and chlorophyll radical anions

Journal Article · Wed Dec 09 23:00:00 EST 1992 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100204a026· OSTI ID:6862246

Perng, J H; Bocian, D F ^[1]

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1. Univ. of California, Riverside (United States)

Resonance Raman (RR) spectra are reported for the anions Zn(OEC)[sup [minus]], OEC[sup [minus]] (OEC = octaehylchlorin), Chl[sup [minus]] (Chl = chlorophyll a), and Pheo[sup [minus]] (Pheo = pheophytin a). The reduction of Zn(OEC) and OEC leads to relatively small shifts in the frequencies (most less than 5 cm[sup [minus]]) of the skeletal modes of the macrocycles. These results indicate that reduction of the chlorins does not result in large structural perturbations. In contrast, reduction of Chl and Pheo leads to large shifts in the frequencies of a number of the vibrational modes of the ring. The C[sub 9]=O-keto group on ring V appears to be the key structural element in facilitating these perturbations. The C[sub 9]O keto stretching modes of Chl and Pheo downshift by 26 and 41 cm[sup [minus]1], respectively. The C[sub b]C[sub b] stretching vibrations of the two rings upshift by about 10 cm[sup [minus]1]. These observations indicate that reduction of the photosynthetic pigments results in significant structural and/or electronic perturbations of the macrocycle. The observation that the C[sub 9]=O Keto and C[sub b]C[sub b] stretching vibrations undergo relatively large shifts upon reduction of the photosynthetic macrocycles suggests that these modes might serve as benchmarks for anion formation in vivo. This should facilitate time-resolved RR studies on photosynthetic proteins. 56 refs., 9 figs., 2 tabs.

• OSTI ID: 6862246
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 96:25; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400 -- Electrochemistry
ABSORPTION SPECTRA
ANIONS
CARBOXYLIC ACIDS
CHARGED PARTICLES
CHEMICAL REACTIONS
CHEMISTRY
CHLOROPHYLL
ELECTROCHEMISTRY
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
IONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PHYTOCHROMES
PIGMENTS
PORPHYRINS
PROTEINS
RADICALS
RAMAN SPECTRA
REDOX POTENTIAL
SPECTRA
SYNTHESIS