Oxygen Adducts of Co‐Phthalocyanine

Kontarinis, Dionysios; Paraskevas, S. M.; Paraskevas, M.

doi:10.1081/sim-120024316

Cited by 3 publications

(3 citation statements)

References 14 publications

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“…The resulting composites were examined using EPR and XPS. Basing the analysis on previous EPR spectra collected by Assour [95] and Parakevas et al [124], the EPR of the unmodified CoPcs do not present strong signals at room temperature due to the presence of low spin Co(II). CNT on its own is reported to exhibit strong effects due to defects in the graphene structure [125] with a g factor comparable with previous analyses [64].…”

Section: Cobalt Macrocyclesmentioning

confidence: 93%

Penta-coordinated transition metal macrocycles as electrocatalysts for the oxygen reduction reaction

Govan

Orellana

Zagal

et al. 2020

J Solid State Electrochem

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The oxygen reduction reaction (ORR) is a highly important reaction in electrochemistry. The following short review details recent advances in novel non-precious metal catalysts containing transition metal macrocycles for use in the ORR. Unbound, many of these electrodes were found to generate high levels of side products such as O 2 − and H 2 O 2 via 2-electron processes, and for this reason, it is aimed to create systems which would favor a 4-electron process which would completely convert oxygen to H 2 O. The 4electron reduction of O 2 releases the most energy in a fuel cell. Novel catalytic materials containing metal macrocycles were created mimicking the structure of enzyme metal centers, the metal in the macrocycle bound to a fifth axial ligand. These structures were observed to exhibit improved catalytic activity, and in the case of cobalt, phthalocyanine systems were observed to move away from the inefficient 2-electron process towards the more complete 4-electron process in alkaline media. Both experimental results (XPS, EPR, cyclic voltammetry and polarization curves) and theoretical models were gathered for various pentacoordinate systems and various electronic effects of the axial ligand on metal center were proposed. Penta-coordinate macrocycles are an important tool for further manipulating and tuning the electronic behavior of transition metal centers for catalysis of the ORR.

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Section: Cobalt Macrocyclesmentioning

confidence: 93%

Penta-coordinated transition metal macrocycles as electrocatalysts for the oxygen reduction reaction

Govan

Orellana

Zagal

et al. 2020

J Solid State Electrochem

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“…Additionally, rather complicated is the chemistry of the CoPcs with O 2 , which in some cases requires the presence of H 2 O 2 to afford the adduct formation [31]; the formation of a transient O 2…”

Section: Metallophthalocyanines As Redox Catalysts: An Overviewmentioning

confidence: 99%

Metallophthalocyanines as Catalysts in Aerobic Oxidation

et al. 2021

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The first remarkable property associated to metallophthalocyanines (MPcs) was their chemical “inertness”, which made and make them very attractive as stable and durable industrial dyes. Nevertheless, their rich redox chemistry was also explored in the last decades, making available a solid and detailed knowledge background for further studies on the suitability of MPcs as redox catalysts. An overlook of MPcs and their catalytic activity with dioxygen as oxidants will be discussed here with a special emphasis on the last decade. The mini-review begins with a short introduction to phthalocyanines, from their structure to their main features, going then through the redox chemistry of metallophthalocyanines and their catalytic activity in aerobic oxidation reactions. The most significant systems described in the literature comprise the oxidation of organosulfur compounds such as thiols and thiophenes, the functionalization of alkyl arenes, alcohols, olefins, among other substrates.

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“…The EPR spectra of 8(2-Et-C 6 H 11 O)CoPc, CoPc, and 16(F)CoPC molecules do not present strong EPR signals at room temperature but only features at around 2000 G corresponding to the presence of the low spin form of Co(II) (Figure 2A). Co phthalocyanines EPR spectra were previously studied in details by Assour (1965), and Kontarinis et al (2003). The EPR spectrum of the complexes in the presence of CNT, are shown in Figure 2B.…”

Section: Epr and Xps Characterizationmentioning

confidence: 99%

Oxygen Reduction Reaction at Penta-Coordinated Co Phthalocyanines

et al. 2020

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From the early 60s, Co complexes, especially Co phthalocyanines (CoPc) have been extensively studied as electrocatalysts for the oxygen reduction reaction (ORR). Generally, they promote the 2-electron reduction of O 2 to give peroxide whereas the 4-electron reduction is preferred for fuel cell applications. Still, Co complexes are of interest because depending on the chemical environment of the Co metal centers either promote the 2-electron transfer process or the 4-electron transfer. In this study, we synthetized 3 different Co catalysts where Co is coordinated to 5 N atoms using CoN4 phthalocyanines with a pyridine axial linker anchored to carbon nanotubes. We tested complexes with electro-withdrawing or electro-donating residues on the N4 phthalocyanine ligand. The catalysts were characterized by EPR and XPS spectroscopy. Ab initio calculations, Koutecky-Levich extrapolation and Tafel plots confirm that the pyridine back ligand increases the CoO 2 binding energy, and therefore promotes the 4-electron reduction of O 2. But the presence of electron withdrawing residues, in the plane of the tetra N atoms coordinating the Co, does not further increase the activity of the compounds because of pull-push electronic effects.

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Oxygen Adducts of Co‐Phthalocyanine

Abstract: A novel complexation of Co-phthalocyanine, with ethylenediamine (en) is described. By this method a macromolecular product is formed. This product absorbs oxygen in aprotic solvents and the existence of a -Co -O -O -Co -bond is suggested.

Cited by 3 publications

References 14 publications

Penta-coordinated transition metal macrocycles as electrocatalysts for the oxygen reduction reaction

Penta-coordinated transition metal macrocycles as electrocatalysts for the oxygen reduction reaction

Metallophthalocyanines as Catalysts in Aerobic Oxidation

Oxygen Reduction Reaction at Penta-Coordinated Co Phthalocyanines

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