Cation and Anion Radicals of (5,15-Dimethyl-2,3,7,8,12,13,17,18-octaethyl-5H,15H- porphinato)nickel(II): Comparison of the Nickel Complexes of Porphodimethene and Chlorin Chromophores

Renner, Mark W.; Buchler, Johann W.

doi:10.1021/j100020a030

Cited by 20 publications

(8 citation statements)

References 16 publications

(22 reference statements)

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“…The absorption spectrum, which shows two broad bands at 482 nm (e 48 100) and 594 (30 700), resembles that of 5,15-dimethyl-2,3,7,8,12,13,17,18-octaethyl-5H,15H-porphinato)nickel(II). 6 The 1 H NMR spectrum, which features two sets of methyl protons [d 1.74 (d, 12H), 2.11 (s, 12H)] and one set of isopropyl methine protons [d 4.42 (septet, 2H)], is consistent with the observed symmetrical structure.…”

supporting

confidence: 59%

Novel products from bromination reactions of 5,10,15,20-tetraisopropylporphyrins

Nelson¹,

Khoury²,

Nurco³

et al. 1998

Chem. Commun.

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supporting

confidence: 59%

Novel products from bromination reactions of 5,10,15,20-tetraisopropylporphyrins

Nelson¹,

Khoury²,

Nurco³

et al. 1998

Chem. Commun.

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Section: Resultssupporting

confidence: 73%

“…This similarity between potentials for the one-electron reduction of NiTPPCl 8 at E 1/2 = −0.82 V and the proposed electrogenerated porphodimethene product generated from 2 (E 1/2 = −0.88 V) is not unexpected on the basis of data in the literature showing almost identical reduction potentials for freebase dodecaphenylporphyrin (E 1/2 = −1.28 V) and its dodecaphenylporphodimethene product (E 1/2 = −1.30 V) in CH 2 Cl 2 31 or between the first one-electron reduction of NiOEP in CH 2 Cl 2 (E 1/2 = −1.46 V) and the meso-dimethyl Ni(II) porphodimethene product in the same solvent (E 1/2 = −1.52 V). 32 In summary, the spectral changes in Figure 10a coupled with the lack of isosbestic points can be interpreted as an initial generation of the deprotonated porphyrin followed by a chemical oxidation or photooxidation 33 of the tetraanionic porphyrin to give the porpho-5,15-bis-paraquinone methide product. Two forms of the porphyrin are also seen in Figure 10b, where porphodimethene and porpho-5,15-bis-paraquinone are both electrochemically generated in the thin-layer cell, but this does not occur under the conditions of Figure 10c, where only the fully protonated porphodimethene can be spectroscopically detected.…”

Section: Niporx 2py (Py) Niporxmentioning

confidence: 92%

Synthesis, Electrochemistry, and Reversible Interconversion among Perhalogenated Hydroxyphenyl Ni(II) Porphyrins, Porphodimethenes, and Porpho-5,15-bis-paraquinone Methide

et al. 2019

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Two octahalogenated nickel(II) hydroxyphenylporphyrins were synthesized and characterized as to their electrochemical and spectroscopic properties as well as their reactivity in neutral, acidic, and basic nonaqueous media. The newly synthesized complexes are represented as NiPorCl8 and NiPorBr8, where Por is the dianion of meso-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin. The UV–vis spectra of NiPorCl8 and NiPorBr8 vary with the solvent and degree of axial coordination but are almost identical to each other in a given solvent. These spectra are also substantially different from that of the unhalogenated NiPor parent porphyrin (which resembles nickel tetraphenylporphyrin, NiTPP), and they also differ from the spectra of β-octahalogenated NiTPPCl8 and NiTPPBr8 under the same solution conditions. The NiPorX8 spectra are stable with time and interpreted in terms of 4- or 6-coordinate derivatives in 13 different nonaqueous solvents. This is not the case, however, in DMF or DMSO, where a transient six-coordinate complex is initially formed upon dissolving the NiPorCl8, followed by the formation of an air-oxidized porphodimethene-like product called porpho-5,15-bis-paraquinone methide, with the time of this chemical transformation depending upon the concentration of the porphyrin in solution. The initial species formed from NiPorCl8 and NiPorBr8 after the first one-electron addition in CH2Cl2 is stable for short times at −60 °C, but this is not the case at room temperature, where a rapid homogeneous chemical reaction occurs. Four additional redox reactions are also observed in CH2Cl2, and the UV–visible spectra of several in-situ-generated electroreduction products are compared with that of chemically synthesized porphodimethenes formed in neutral, acidic, and basic solutions of CH2Cl2 containing acid in the form of TFA or base in the form of TBA+X, where X = OAc–, CN–, and OH–. Finally, a reversible electrochemically driven conversion between the Ni(II) hydroxyphenylporphyrin and a reduced porphodimethene or oxidized porphyrin-like product, porpho-5,15-bis-paraquinone methide, is described.

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“…In Figure , which shows the absorbance−time profiles for NiTPP with initial concentration of 100 mg/L, the quantity of intermediate increased to a maximum (at about 20 min) and then decreased during sonication time. This intermediate is most likely a π-cation radical (TPP • ) + as previously suggested. − Cation radicals have been shown to be intermediates in reactions of metalloporphyrins with hydrogen peroxide . Furthermore, similar experimental trends were found in the decomposition of VOTPP with an intensive absorption peak at a wavelength of 548 nm for pure VOTPP (see Table ) and a new peak at 650 nm during sonication process.…”

Section: Resultssupporting

confidence: 72%

The Feasibility Studies for Radical-Induced Decomposition and Demetalation of Metalloporphyrins by Ultrasonication

Yen

2000

Energy Fuels

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A feasibility study of the decomposition and demetalation of metalloporphyrins by ultrasonic irradiation process in the presence of radical-induced reactions is presented in this paper. Two representative model compounds, NiTPP and VOTPP, were investigated in this ultrasonic process on the laboratory scale. The extent of the decomposition was determined by UV−vis, while the metal analysis was measured by ICP/MS. In the initial investigation, the decomposition of metalloporphyrins, which were dissolved in different solvent−water mixtures, was performed under the ultrasonication process. Among these solvents, the chlorinated-type solvents (e.g., chloroform and dichloromethane) achieved a higher efficiency because they generated more oxidizing species under sonication at 20 kHz frequency. Other additives such as surfactant and hydrogen peroxide, which affect the decomposition efficiency, were also investigated. Under optimal condition, the decomposition efficiency reached about 90% in 1 h for both model compounds. An oxidative intermediate existed for both metalloporphyrins under ultrasonication. The decomposition reaction rates of these two compounds followed pseudo-first-order in reactant concentration and were inhibited by initial feed concentration. The dependence of the rate constants on the different initial concentrations could be determined by the Langmuir−Hinshelwood equation.

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Cation and Anion Radicals of (5,15-Dimethyl-2,3,7,8,12,13,17,18-octaethyl-5H,15H- porphinato)nickel(II): Comparison of the Nickel Complexes of Porphodimethene and Chlorin Chromophores

Cited by 20 publications

References 16 publications

Novel products from bromination reactions of 5,10,15,20-tetraisopropylporphyrins

Novel products from bromination reactions of 5,10,15,20-tetraisopropylporphyrins

Synthesis, Electrochemistry, and Reversible Interconversion among Perhalogenated Hydroxyphenyl Ni(II) Porphyrins, Porphodimethenes, and Porpho-5,15-bis-paraquinone Methide

The Feasibility Studies for Radical-Induced Decomposition and Demetalation of Metalloporphyrins by Ultrasonication

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