Site of one-electron reduction of nickel(II) porphyrins:  formation of nickel(I) porphyrin or nickel(II) porphyrin .pi.-radical anion

Nahor, Gad S.; Neta, P.; Hambright, Peter; Robinson, L. R.; Harriman, Anthony

doi:10.1021/j100380a026

Cited by 22 publications

(23 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This result was confirmed by Nahor et al, 19 though they did observe that some nickel porphyrins could form π-anion radicals. These factors were studied in more detail by Kadish et al 14,15 The product of the second redox process has not been studied in detail.…”

supporting

confidence: 66%

“…Bleaching of the Soret band and a broad band between 600 and 750 nm are frequently an indication of a π-anion radical. 19 There were similarities and differences between Ni(OEPone) − and Zn(OEPone) − , which is known to form a π-anion radical species. Although Zn(OEPone) − has a broad band at 452 nm, the Soret band was not split as in the nickel complex.…”

Section: Cyclic Voltammetry and Spectroelectrochemistry Of Nickel Octmentioning

confidence: 99%

See 1 more Smart Citation

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

Atifi

2015

Anal. Chem.

View full text Add to dashboard Cite

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.

show abstract

supporting

confidence: 66%

Section: Cyclic Voltammetry and Spectroelectrochemistry Of Nickel Octmentioning

confidence: 99%

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

Atifi

2015

Anal. Chem.

View full text Add to dashboard Cite

show abstract

“…Indeed, reduction to Ni(I)-TBP was observed. Possibly, the Ni(I)-TBP produced under slightly acidic conditions undergoes rapid disproportionation to yield the original Ni(II)-TBP and a product which is doubly reduced at the porphyrin ring, as suggested for other Ni(I)-porphyrins found in the TPP series [54].…”

Section: Reduction Of Tetrabenzoporphyrinsmentioning

confidence: 93%

Tetrabenzoporphyrins: Metal Incorporation and Exchange Kinetics, Ligational Equilibria and Pulse Radiolysis Studies

Cromer

Hambright

Grodkowski

et al. 1997

J. Porphyrins Phthalocyanines

Self Cite

View full text Add to dashboard Cite

The solution chemistry of tetrabenzoporphyrin ( TBP ) and several of its metal derivatives were compared with that of the corresponding octaethylporphyrins. Kinetic studies were done on zinc and cadmium ion incorporation and the exchange reactions of cadmium porphyrins with zinc. Formation constants of Cd (II), Cu (II), VO (IV), Ni (II), Zn (II) and Mg (II) porphyrins with pyridine were determined for both compounds. The spectra of the radical cations of Ni (II), Mg (II) and H 2- TBP were obtained, as well as that of the radical anion of Mg (II)- TBP . Aside from the new Ni (I)- TBP , no long-lived intermediates, as noted with other porphyrins, were observed upon reduction of the tetrabenzoporphyrins. The low basicity and rigidity of the tetrabenzoporphyrin nucleus may explain many of its relative reactivity properties.

show abstract

“…Although the neutral radical species have not yet been identified experimentally, this reaction pathway is suggested for more reactive singly reduced porphyrins and in acidic solution . The stability of porphyrin radical anions depends on the nature of the metal center, the substitution of the macrocycle, and the solvent pH . In particular, the relative electron density on the porphyrin ring and the stabilization of the singly reduced state by, for example, inductive and mesomeric effects with peripheral substituents, impact the stability of the radical anion.…”

Section: Introductionmentioning

confidence: 99%

“…The one‐electron reduction of nickel(II) porphyrins in aqueous solution was examined mostly by using radiolytic reduction . The radical anions probably decay by disproportionation to form the original porphyrin and the corresponding dianion, which undergoes rapid protonation towards the chlorin and phlorin anions .…”

Section: Introductionmentioning

confidence: 99%

Spectroelectrochemical Investigation of the One‐Electron Reduction of Nonplanar Nickel(II) Porphyrins

et al. 2016

View full text Add to dashboard Cite

The electrochemical reduction of a series of nickel porphyrins with an increasing number of substituents was investigated in acetonitrile. A one-electron reduction of [5,15-bis(1-ethylpropyl)porphyrinato]nickel(II) leads to π-anion radicals and to efficient formation of phlorin anions, presumably by disproportionation and subsequent protonation of the doubly reduced species. The phlorin anion was identified by using cyclic voltammetry and UV/Vis and resonance Raman spectroelectrochemistry, complemented by quantum-chemical calculations to assign the spectral signatures. The theoretical analysis of the potential-energy landscape of the singly reduced species suggests a thermally activated intersystem crossing that populates the quartet state and thus lowers the energy barrier towards disproportionation channels. Structure-reactivity correlations are investigated by considering different substitution patterns of the investigated nickel(II) porphyrin cores, that is, for the porphyrin with additional β-aryl ([5,15-bis(1-ethylpropyl)-2,8,12,18-tetra(p-tolyl)porphyrinato]nickel(II)) and meso-alkyl substitution ([5,10,15,20-tetrakis(1-ethylpropyl)porphyrinato]nickel(II)), no phlorin anion formation was observed under electrochemical conditions. This observation is correlated either to kinetic inhibition of the disproportionation reaction or to lower reactivity of the subsequently formed doubly reduced species towards protonation.

show abstract

Site of one-electron reduction of nickel(II) porphyrins: formation of nickel(I) porphyrin or nickel(II) porphyrin .pi.-radical anion

Cited by 22 publications

References 0 publications

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

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

Tetrabenzoporphyrins: Metal Incorporation and Exchange Kinetics, Ligational Equilibria and Pulse Radiolysis Studies

Spectroelectrochemical Investigation of the One‐Electron Reduction of Nonplanar Nickel(II) Porphyrins

Contact Info

Product

Resources

About