Infrared spectroscopy of oxidized metalloporphyrins: detection of a band diagnostic of porphyrin-centered oxidation

Shimomura, Eric T.; Phillippi, Martin A.; Goff, Harold M.; Scholz, William F.; Reed, Christopher A.

doi:10.1021/ja00412a055

Cited by 124 publications

(70 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The data presented above clearly supports previous workers' conclusions that infrared spectroscopy is a valuable tool for ascertaining the site of oxidation in TPP complexes (1,2), and further demonstrate that such useful diagnostic evidence can be obtained in situ without isolation of the oxidized complexes. In addition to the obvious factor of convenience, in-situ characterization affords a difference spectrum in which small vibrational perturbations due to oxidation of the complexes are more likely to be observed than in single spectra of isolated species.…”

Section: Discussionsupporting

confidence: 88%

In-situ Fourier transform infrared spectroelectrochemical studies of the oxidation of some tetraphenylporphyrin complexes

Hinman¹,

Pavelich²,

McGarty³

1988

Can. J. Chem.

View full text Add to dashboard Cite

In-situ FTIR spectroelectrochemistry has been applied to determine difference spectra in the region 1800 to 1000 cm−1 associated with the oxidation of TPPH2, TPPMg, TPPCu, TPPZn, TPPCo, TPPMnCl, and TPPFeCl. In all cases, formation of the π-cation radical results in two characteristic absorbance decreases near 1600 and 1485 cm−1, and five characteristic absorbance increases near 1415, 1350, 1285, 1225, and 1005 cm−1. Formation of the π-dication was observed for TPPZn, TPPMg, and TPPCo, and gave rise to a new absorbance increase near 1600 cm−1, and a shift to higher frequency of bands in the 1200 to 1400 cm−1 region. Perchlorate coordination to oxidized TPPZn, TPPMg, and TPPCo gives rise to bands near 1140 and 1030 cm−1.

show abstract

Section: Discussionsupporting

confidence: 88%

In-situ Fourier transform infrared spectroelectrochemical studies of the oxidation of some tetraphenylporphyrin complexes

Hinman¹,

Pavelich²,

McGarty³

1988

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…However, overlapping IR bands of oxidants and the instability of BChl-b considerably limit this access to model-compound spectra. A much more appropriate approach would be the electrochemical generation of radicals in a cell suited to IR spectroscopy (15,16). In a previous report (17), we have described an optically and IR transmitting, anaerobic, thin-layer electrochemical cell that allows Chl radicals to be generated and investigated in situ.…”

mentioning

confidence: 99%

Infrared spectroelectrochemistry of bacteriochlorophylls and bacteriopheophytins: Implications for the binding of the pigments in the reaction center from photosynthetic bacteria

Mäntele

Wollenweber

Nabedryk³

et al. 1988

Proc. Natl. Acad. Sci. U.S.A.

131

140

View full text Add to dashboard Cite

The IR spectra of the bacteriochlorophyll a and b cations and the bacteriopheophytin a and b anions were obtained by using an ER and optically transparent electrochemical cell. Prominent effects of radical formation on the vibrational spectra were found for bands assigned to the ester, keto, and acetyl C=O groups and for vibrations from macrocycle bonds. The (radical-minus-neutral) difference spectra are compared to the light-induced difference spectra ofthe primary donor photooxidation and the intermediary acceptor photoreduction in the reaction center of photosynthetic bacteria. Light-induced absorbance changes from bacteriochlorophyll a-containing reaction centers bear striking similarities to the electrochemically induced absorbance changes observed upon formation ofbacteriochlorophyll a' in vitro. Comparison ofthe radical formation in vitro in a hydrogen-bonding or a nonhydrogen-bonding solvent suggests an ester C=O group hydrogen bonded in the neutral state but free in the cation state. For the keto C=O group, the same comparison indicates one free carbonyl group. The (anion-minus-neutral) difference spectra of bacteriopheophytin a and b exhibit a single band in the ester C=O frequency range. In contrast, two bands are observed in the difference spectra of the intermediary acceptor reduction in the reaction center of Rhodopseudomonas viridis.The higher frequency band exhibits a sensitivity to 'H-2H exchange, which suggests a contribution from a protonated carboxyl group of an amino acid side chain.In the primary events in photosynthesis, absorption of light leads to charge separation between electron donor and acceptor molecules. In the bacterial reaction center (RC), the primary electron donor (P) is a bacteriochlorophyll (BChl)-a or -b dimer, the intermediary electron acceptor (H) is a bacteriopheophytin (BPheo)-a or -b monomer, and the primary acceptor is a quinone. Spectroscopic data on these components have been reported (1-3), and, together with the high-resolution structure analysis (4-7), electron transport pathways can be visualized. Specific interactions of the pigment molecules with their polypeptide environment, in addition to pigment-pigment interactions, account for the spectral and redox properties of BChls in vivo. Among these interactions are external liganding to the Mg atom ofthe BChl (8) as well as hydrogen-bonding from pigment groups to polypeptide side chains (7,8). Although such interactions have been studied by resonance Raman (RR) and IR spectroscopy in model systems (8,9), details about the interactions in vivo both in the neutral and charge-separated state still have to be collected.In previous studies, we have used IR difference spectroscopy to investigate the molecular changes in bacterial RC and chromatophores concomitant with P photooxidation (10) as well as with H reduction (11). By using Fourier transform infrared (FTIR) difference spectroscopy, sensitivity can be high enough to detect single bonds. The light-induced FTIR difference spectra consist of a number ofcha...

show abstract

“…Thus, the presence of the porphyrin in the electrodeposited film is demonstrated through a group of bands assigned to the porphyrin skeletal modes located at 1010, 1040, 1124, 1180, 1228 and 1267 cm −1 [26]. Moreover, the band at 1267 cm −1 indicates the existence of the porphyrin ring as radical [26][27][28][29].…”

Section: Ftir Spectroscopy Of Co-porphyrin-miementioning

confidence: 94%

Oxygen storage/release in cobalt porphyrin electrodeposited films

Pérez-Morales

Miguel

Muñoz

et al. 2009

Electrochimica Acta

View full text Add to dashboard Cite

Infrared spectroscopy of oxidized metalloporphyrins: detection of a band diagnostic of porphyrin-centered oxidation

Cited by 124 publications

References 0 publications

In-situ Fourier transform infrared spectroelectrochemical studies of the oxidation of some tetraphenylporphyrin complexes

In-situ Fourier transform infrared spectroelectrochemical studies of the oxidation of some tetraphenylporphyrin complexes

Infrared spectroelectrochemistry of bacteriochlorophylls and bacteriopheophytins: Implications for the binding of the pigments in the reaction center from photosynthetic bacteria

Oxygen storage/release in cobalt porphyrin electrodeposited films

Contact Info

Product

Resources

About