Resonance Raman spectroscopy reveals a1u vs. a2u character and pseudo-Jahn-Teller distortion in radical cations of nickel(II), copper(II), and chloroiron(III) octaethyl- and tetraphenylporphyrins

Czernuszewicz, Roman S.; Macor, Kathleen A.; Li, Xiaoyuan; Kincaid, James R.; Spiro, Thomas G.

doi:10.1021/ja00193a017

Cited by 143 publications

(131 citation statements)

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“…The feather extracts fluoresced at 780 and 1064 nm excitation and did not produce informative Raman spectra. In contrast, rsif.royalsocietypublishing.org J R Soc Interface 10: 20121065 spectra from the turaco, bokmakierie and parrot feathers were characteristic of a porphyrin, carotenoid and psittacofulvin, respectively [35,38]. Rufous-brown barbs in the robin feather fluoresced at both 780 and 1064 nm excitation; 780 nm excitation induced a sinusoidal disturbance of the baseline between 200 and approximately 1600 nm for all brown feather pigments, i.e.…”

Section: Resultsmentioning

confidence: 94%

Vibrational spectroscopic analyses of unique yellow feather pigments (spheniscins) in penguins

Thomas

McGoverin

McGraw

et al. 2013

J. R. Soc. Interface.

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Many animals extract, synthesize and refine chemicals for colour display, where a range of compounds and structures can produce a diverse colour palette. Feather colours, for example, span the visible spectrum and mostly result from pigments in five chemical classes (carotenoids, melanins, porphyrins, psittacofulvins and metal oxides). However, the pigment that generates the yellow colour of penguin feathers appears to represent a sixth, poorly characterized class of feather pigments. This pigment class, here termed 'spheniscin', is displayed by half of the living penguin genera; the larger and richer colour displays of the pigment are highly attractive. Using Raman and mid-infrared spectroscopies, we analysed yellow feathers from two penguin species (king penguin, Aptenodytes patagonicus; macaroni penguin, Eudyptes chrysolophus) to further characterize spheniscin pigments. The Raman spectrum of spheniscin is distinct from spectra of other feather pigments and exhibits 17 distinctive spectral bands between 300 and 1700 cm 21 . Spectral bands from the yellow pigment are assigned to aromatically bound carbon atoms, and to skeletal modes in an aromatic, heterocyclic ring. It has been suggested that the penguin pigment is a pterin compound; Raman spectra from yellow penguin feathers are broadly consistent with previously reported pterin spectra, although we have not matched it to any known compound. Raman spectroscopy can provide a rapid and non-destructive method for surveying the distribution of different classes of feather pigments in the avian family tree, and for correlating the chemistry of spheniscin with compounds analysed elsewhere. We suggest that the sixth class of feather pigments may have evolved in a stem-lineage penguin and endowed modern penguins with a costly plumage trait that appears to be chemically unique among birds.

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Section: Resultsmentioning

confidence: 94%

Vibrational spectroscopic analyses of unique yellow feather pigments (spheniscins) in penguins

Thomas

McGoverin

McGraw

et al. 2013

J. R. Soc. Interface.

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“…Indeed, both experiments and computations predict an in-plane distortion of the porphyrinic ring of the cation along an a 2g mode (a g in the C 4h group). [29,30,31] This distortion is caused by a pseudo JahnTeller (JT) interaction between the two lowest doublet states of the cation, labeled as 2 A 2u and 2 A 1u in the D 4h group. In this work, we do not investigate the role of this pseudo-JT effect on the ET process, and assume that only the lowest doublet state of the porphyrin cation, i.e.…”

Section: Model Parametersmentioning

confidence: 99%

First-principles study of photoinduced electron-transfer dynamics in a Mg–porphyrin–quinone complex

Borrelli

Domcke

2010

Chemical Physics Letters

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The photoinduced electron-transfer process between a magnesium-porphyrin and a quinone in a model complex has been studied by means of quantum dynamical methods. The microscopic parameters controlling the electrontransfer process have been obtained using ab initio electronic structure calculations. A quantum dynamical simulation for a reduced dimensionality model, including only the totally symmetric vibrational degrees of freedom of the quinone molecule, shows that the electron-transfer is fast, taking place in a few hundreds of femtoseconds, in agreement with experimental results for similar systems.

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“…The product of the first redox couple led to a π-cation radical (Ni II (OEP +• ), as shown by UV-visible, EPR and resonance Raman spectroscopy. [20][21][22] (2) Scheidt and co-workers have shown that mixed valence dimers, [(Ni(OEP)2] + , can also be formed. 23,24 The mixed dimer can be reduced/oxidized at about the same potential as the Ni(OEP) oxidation couple.…”

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confidence: 99%

Spectroscopic Evidence of Nanodomains in THF/RTIL Mixtures: Spectroelectrochemical and Voltammetric Study of Nickel Porphyrins

Atifi

2015

Anal. Chem.

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The presence and effect of RTIL nanodomains in molecular solvent/RTIL mixture were investigated by studying the spectroelectrochemistry and voltammetry of nickel octaethylporphyrin (Ni(OEP)) and nickel octaethylporphinone (Ni(OEPone)). Two oxidation and 2−3 reduction redox couples were observed, and the UV−visible spectra of all stable products in THF and RTIL mixtures were obtained. The E°values for the reduction couples that were studied were linearly correlated with the Gutmann acceptor number, as well as the difference in the E°values between the first two waves (ΔE 12 °= |E 1 °− E 2 °|). The ΔE 12 °for the reduction was much more sensitive to the %RTIL in the mixture than the oxidation, indicating a strong interaction between the RTIL and the anion or dianion. The shifts in the E°values were significantly different between Ni(OEP) and Ni(OEPone). For Ni(OEP), the E 1 °values were less sensitive to the %RTIL than were observed for Ni(OEPone). Variations in the diffusion coefficients of Ni(OEP) and Ni(OEPone) as a function of %RTIL were also investigated, and the results were interpreted in terms of RTIL nanodomains. To observe the effect of solvation on the metalloporphyrin, Ni(OEPone) was chosen because it contains a carbonyl group that can be easily observed in infrared spectroelectrochemistry. It was found that the ν CO band was very sensitive to the solvent environment, and two carbonyl bands were observed for Ni(OEPone) − in mixed THF/RTIL solutions. The higher energy band was attributed to the reduced product in THF, and the lower energy band attributed to the reduced product in the RTIL nanophase. The second band could be observed with as little as 5% of the RTIL. No partitioning of Ni(OEPone) + into the RTIL nanodomain was observed. DFT calculations were carried out to characterize the product of the first reduction. These results provide strong direct evidence of the presence of nanodomains in molecular solvent/RTIL mixtures.

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Resonance Raman spectroscopy reveals a1u vs. a2u character and pseudo-Jahn-Teller distortion in radical cations of nickel(II), copper(II), and chloroiron(III) octaethyl- and tetraphenylporphyrins

Cited by 143 publications

References 4 publications

Vibrational spectroscopic analyses of unique yellow feather pigments (spheniscins) in penguins

Vibrational spectroscopic analyses of unique yellow feather pigments (spheniscins) in penguins

First-principles study of photoinduced electron-transfer dynamics in a Mg–porphyrin–quinone complex

Spectroscopic Evidence of Nanodomains in THF/RTIL Mixtures: Spectroelectrochemical and Voltammetric Study of Nickel Porphyrins

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