The characterization of cobalt(II) derivatives of selected substituted meso-tetraphenyl and tetrapyridyl porphyrins by EPR spectroscopic study

Skrzypek, D.; Madejska, I.; Habdas, Jan

doi:10.1016/j.solidstatesciences.2006.12.005

Cited by 11 publications

(7 citation statements)

References 26 publications

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“…In this configuration, the unpaired electron resides mainly in the d z 2 orbital out of the porphyrin plane formed by the N ligands. 49,50 The absence of superhyperfine interactions with the four surrounding N nuclei, observed in contrast for the Cu derivatives, supports this scenario.…”

Section: ■ Results and Discussionmentioning

confidence: 68%

“…In addition, EXAFS shows an improvement in the fit quality upon addition of a Co–O bond at 2.34–2.57 Å (see section S10 in the Supporting Information). In this configuration, the unpaired electron resides mainly in the d z 2 orbital out of the porphyrin plane formed by the N ligands. , The absence of superhyperfine interactions with the four surrounding N nuclei, observed in contrast for the Cu derivatives, supports this scenario.…”

Section: Results and Discussionmentioning

confidence: 80%

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Magnetic, Mechanically Interlocked Porphyrin–Carbon Nanotubes for Quantum Computation and Spintronics

et al. 2021

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Atomic-scale reproducibility and tunability endorse magnetic molecules as candidates for spin qubits and spintronics. A major challenge is to implant those molecular spins into circuit geometries that may allow one, two, or a few spins to be addressed in a controlled way. Here, the formation of mechanically bonded, magnetic porphyrin dimeric rings around carbon nanotubes (mMINTs) is presented. The mechanical bond places the porphyrin magnetic cores in close contact with the carbon nanotube without disturbing their structures. A combination of spectroscopic techniques shows that the magnetic geometry of the dimers is preserved upon formation of the macrocycle and the mMINT. Moreover, the metallic core selection determines the spin location in the mMINT. The suitability of mMINTs as qubits is explored by measuring their quantum coherence times (T m). Formation of the dimeric ring preserves the T m found in the monomer, which remains in the μs scale for mMINTs. The carbon nanotube is used as vessel to place the molecules in complex circuits. This strategy can be extended to other families of magnetic molecules. The size and composition of the macrocycle can be tailored to modulate magnetic interactions between the cores and to introduce magnetic asymmetries (heterometallic dimers) for more complex molecule-based qubits.

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Section: ■ Results and Discussionmentioning

confidence: 68%

Section: Results and Discussionmentioning

confidence: 80%

Magnetic, Mechanically Interlocked Porphyrin–Carbon Nanotubes for Quantum Computation and Spintronics

et al. 2021

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“…We earlier examined Au(III) and Au(II) quinoxalinoporphyrins , and now turn our attention to the cobalt derivatives which can exist in Co(III), Co(II), and Co(I) oxidation states under the appropriate application of an oxidizing or reducing potential. Numerous synthetic cobalt porphyrins with a variety of meso and β-pyrrolic substituents have been studied as to their spectroscopic and electrochemical properties under different solution conditions, − but cobalt quinoxalinoporphyrins have never before been characterized.…”

Section: Introductionmentioning

confidence: 99%

Electrochemistry and Spectroelectrochemistry of β,β′-Fused Quinoxalinoporphyrins and Related Extended Bis-porphyrins with Co(III), Co(II), and Co(I) Central Metal Ions

Zhu

Sintic

et al. 2009

Inorg. Chem.

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A series of cobalt(II) and cobalt(III) porphyrins with fused quinoxaline rings at one or more beta,beta'-pyrrolic units of the macrocycle were synthesized and characterized as to their electrochemical properties in nonaqueous media. Their UV-visible spectra were also measured before and during oxidation or reduction in a thin-layer cell. The investigated quinoxalinoporphyrins are represented as (PQ)Co, (QPQ)CoCl, (PQ(2))CoCl, Co(P)-TA-(P)Co, and Co(PQ)-(QP)Co, where PQ = the dianion of 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)-quinoxalino[2,3-b']porphyrin, QPQ = the dianion of the corresponding linear bisquinoxalino[2,3-b':12,13-b'']porphyrin, PQ(2) = the dianion of the corresponding corner bisquinoxalino[2,3-b':7,8-b'']porphyrin, and (P)-TA-(P) = the tetraanion of the bis-porphyrin with 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)porphyrins fused at opposite ends of tetraazaanthracene. (P)Co and (P)CoCl were also characterized where P = the dianion of 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)porphyrin. Each compound could be cycled between their Co(III), Co(II), and Co(I) forms under the application of a given oxidizing or reducing potential, although a one-electron reduction of the Co(II) quinoxalinoporphyrins led to a product with mixed Co(I) and porphyrin pi-anion radical character followed by generation of a pure Co(I) pi-anion radical species at more negative potentials. The effect of the position and number of quinoxaline groups on the redox potentials and mechanisms of each electron transfer were elucidated, and comparisons made to structurally similar compounds containing both redox active and redox inactive central metal ions. Surprisingly, the position and number of quinoxaline groups on the macrocycle has little or no effect on the redox potentials for the Co(II) --> Co(III) or Co(III) --> Co(II) processes, but this is not the case for other electron transfer reactions where significant differences are seen between the examined compounds. Significant interactions are also observed between the two porphyrin macrocycles of the laterally bridged dicobalt(II) bis-porphyrin dyad Co(P)-TA-(P)Co in its singly and doubly reduced form, but only weak interactions are seen between the two Co(PQ) units of the single bond biquinolalinyl-bridged dicobalt(II) bis-porphyrin dyad Co(PQ)-(QP)Co.

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“…It is important to note a number of features of the electrochemical conversion of studied Co-complexes in the argon atmosphere: -A couple of cathodic and anodic maxima related to the redox process of the central metal Co 2+ ↔ Co 3+ in the potential range of 0.0 ÷ 0.4 V is determined; -On the cathodic fragment of cyclic voltamperograms a low-intensity reduction wave of oxygen adsorbed on Co complexes in the potential range of -0.1 ÷ -0.4 V is observed. It is known that Co complexes are characterized by the tendency to the formation of oxygen adducts Co-O 2 , that is confirmed by electron paramagnetic resonance spectra [21]; -For all the studied Co-complexes redox-potentials of conversion processes of Co and macrocycle via the first step (L ↔ L -· ) were unchanged. Therefore, for structures of the similar type, when the isomerism deals with the pyridyl groups, its influence was slowly.…”

Section: Electrochemical Properties Of a Free Porphyrin H 2 (Py-3) 2 mentioning

confidence: 56%

Electrochemical behavior of a number of bispyridyl-substituted porphyrins and their electrocatalytic activity in molecular oxygen reduction reaction

Berezina

Базанов

et al. 2016

J. Porphyrins Phthalocyanines

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ABSTRACT:The investigation of electrochemical properties of active layers containing 5,15-bis(pyrid-3-yl) -3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphine, [5,15-bis(pyrid-3-yl)-3,7,13,17-tetramethyl-2,8,12, 18-tetraethylporphinato]cobalt(II), bispyridine [5,15-bis(pyrid-3-yl)-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphinato]cobalt(III), [5,15-bis(pyrid-4-yl)-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphinato]cobalt(II) and bispyridine [5,15-bis(pyrid-4-yl)-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphinato]cobalt(III) in 0.1 M KOH aqueous solution has been carried out by cyclic voltammetry. The potential ranges of redox processes related to the transformation of the porphyrin macrocycle, pyridyl substituents and central metal have been established. The electrochemical parameters of oxygen electroreduction reaction (the half-wave potential -E 1/2 (O 2 ), the maximum potential -E p (O 2 ), the current density -j, the activation energy -E act ) have been determined. It was shown that all porphyrins exhibit the catalytic activity. The electroreduction process of oxygen on electrode with the porphyrin-ligand occurs via 2-electron mechanism to give hydrogen peroxide ion HO 2 -, and on ones with the cobalt porphyrins -via parallel-sequential pathway including 2-electron and 4-electron processes to give HO 2 -, OH -. The presence of pyridine axial ligands in Co-complexes leads to a significant increase of the electrocatalytic activity in molecular oxygen reduction reaction.

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The characterization of cobalt(II) derivatives of selected substituted meso-tetraphenyl and tetrapyridyl porphyrins by EPR spectroscopic study

Cited by 11 publications

References 26 publications

Magnetic, Mechanically Interlocked Porphyrin–Carbon Nanotubes for Quantum Computation and Spintronics

Magnetic, Mechanically Interlocked Porphyrin–Carbon Nanotubes for Quantum Computation and Spintronics

Electrochemistry and Spectroelectrochemistry of β,β′-Fused Quinoxalinoporphyrins and Related Extended Bis-porphyrins with Co(III), Co(II), and Co(I) Central Metal Ions

Electrochemical behavior of a number of bispyridyl-substituted porphyrins and their electrocatalytic activity in molecular oxygen reduction reaction

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