The effect of heat treatment on group VIIIB porphyrins as electrocatalysts in the cathodic reduction of oxygen

Ikeda, Osamu; Fukuda, Hiroshi; Tamura, Hideo

doi:10.1039/f19868201561

Cited by 27 publications

(19 citation statements)

References 4 publications

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“…Carbon supported iridium porphyrins are the only known mono-metal chelates that catalyze the direct four-electron reduction of O 2 in acid [415][416][417][418]. van Veen and co-workers [417] have report that the support affects the O 2 reduction selectivity.…”

Section: Two To Four-electron Reduction Catalysts For the Reduction Omentioning

confidence: 97%

Metallophthalocyanine-based molecular materials as catalysts for electrochemical reactions

Zagal¹,

Griveau²,

Silva³

et al. 2010

Coordination Chemistry Reviews

542

415

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Section: Two To Four-electron Reduction Catalysts For the Reduction Omentioning

confidence: 97%

Metallophthalocyanine-based molecular materials as catalysts for electrochemical reactions

Zagal¹,

Griveau²,

Silva³

et al. 2010

Coordination Chemistry Reviews

542

415

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“…For metalloporphyrin complexes, this is likely due to the formation of metal carbides during combustion. 65 X-ray Single-Crystal Structure Determination. The crystal evaluation and data collection were performed at 173 K on a Bruker APEX II CCD diffractometer using Mo Kα radiation (λ = 0.71073 Å).…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Comparative Study of Rhodium and Iridium Porphyrin Diaminocarbene and N-Heterocyclic Carbene Complexes

2014

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Iridium meso-tetratolylporphyrinato (TTP) mono-and bis-diaminocarbene complexes, [Ir(TTP)[═C(NHBn)(NHR)]2-x(C≡NBn)x]BF4, where R = Bn, n-Bu and x = 1, 0, were synthesized by nucleophilic addition of amines to the bis-isocyanide complex [Ir(TTP)(C≡NBn)2]BF4. Rhodium and iridium porphyrinato N-heterocyclic carbene (NHC) complexes M(TTP)CH3(NHC), where NHC = 1,3-diethylimidazolylidene (deim) or 1-(n-butyl)-3-methylimidazolylidene (bmim), were prepared by the addition of the free NHC to M(TTP)CH3. The NHC complexes displayed two dynamic processes by variable-temperature NMR: meso-aryl-porphyrin CC bond rotation and NHC exchange. meso-Aryl-porphyrin CC bond rotation was exhibited by both rhodium and iridium complexes at temperatures ranging between 239 and 325 K. Coalescence data for four different complexes revealed ΔG⧧ROT values of 59 ± 2 to 63 ± 1 kJ•mol-1. These relatively low rotation barriers may result from ruffling distortions in the porphyrin core, which were observed in the molecular structures of the rhodium and iridium bmim complexes. Examination of NHC exchange with rhodium complexes by NMR line-shape analyses revealed rate constants of 3.72 ± 0.04 to 32 ± 6 s-1 for deim displacement by bmim (forward reaction) and 2.7 ± 0.4 to 18 ± 2 s-1 for bmim displacement by deim (reverse reaction) at temperatures between 282 and 295 K, corresponding to ΔGf⧧ of 65.2 ± 0.6 kJ•mol-1 and ΔGr⧧ of 66.2 ± 0.5 kJ•mol-1, respectively. Rates of NHC exchange with iridium were far slower, with first-order dissociation rate constants of (1.75 ± 0.04) × 10-4 s-1 for the forward reaction and (1.2 ± 0.1) × 10-4 s-1 for the reverse reaction at 297.1 K. These rate constants correspond to ΔG⧧ values of 94.2 ± 0.6 and 95.2 ± 0.2 kJ•mol-1 for the forward and reverse reactions, respectively. Equilibrium constants for the exchange reactions were 1.6 ± 0.2 with rhodium and 1.56 ± 0.04 with iridium, favoring the bmim complex in both cases, and the log(K) values for NHC binding to M(TTP)CH3 were 4.5 ± 0.3 (M = Rh) and 5.4 ± 0.5 (M = Ir), as determined by spectrophotometric titrations at 23 °C. The molecular structures also featured unusually long metal-Ccarbene bonds for the bmim complexes (Rh-CNHC: 2.255(3) Å and Ir-CNHC: 2.194(4) Å).

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“…atoms (Fe-N x moiety) embedded on the surface as the active site have been most extensively studied and are one of the promising candidates for the active and reliable catalyst . Several methods have been reported to produce the carbon materials with the Fe-N x active site: (a) heat treatment of a complex usually adsorbed on carbon materials, in which Fe is coordinated by nitrogen atoms in the ligands, such as porphyrins [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29], phthalocyanine [30,31], phenanthroline [32], cynanide [33]; (b) heat treatment of a mixture of Fe salts and a nitrogen-containing polymer such as polypyrrole and polyacrylonitrile with or without carbon black [34][35][36][37][38]; (c) heat treatment of the Fe salts supported on carbon materials in NH 3 or CH 3 CN gases [25,28,39,40]; (d) heat treatment of the Fe salts loaded on carbon materials which are enriched with nitrogen on the surface or formed by carbonization in the NH 3 gas [25,26,41]. We recently formed the noble-metal-free cathode catalysts by carbonizing catalase and hemoglobin [42][43][44].…”

Section: Introductionmentioning

confidence: 99%

Application of nitrogen-rich amino acids to active site generation in oxygen reduction catalyst

Maruyama

Fukui

Kawaguchi

et al. 2008

Journal of Power Sources

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The effect of heat treatment on group VIIIB porphyrins as electrocatalysts in the cathodic reduction of oxygen

Cited by 27 publications

References 4 publications

Metallophthalocyanine-based molecular materials as catalysts for electrochemical reactions

Metallophthalocyanine-based molecular materials as catalysts for electrochemical reactions

Comparative Study of Rhodium and Iridium Porphyrin Diaminocarbene and N-Heterocyclic Carbene Complexes

Application of nitrogen-rich amino acids to active site generation in oxygen reduction catalyst

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