Abstract The oxygen evolution reaction that occurs during water oxidation is of considerable importance as an essential energy conversion for rechargeable metal–air batteries and direct solar splitting. Cost-efficient ABO 3 perovskites have been studied extensively because their high activity the reaction; however, they lack stability, effective solution to this problem has not yet demonstrated. Here we report Fe 4+ -based quadruple perovskite CaCu 4 O 12 activity, which comparable or...

Bifunctional electrocatalysts for oxygen evolution/reduction reaction (OER/ORR) are desirable the development of energy conversion technologies. It is discovered that manganese quadruple perovskites CaMn7 O12 and LaMn7 show bifunctional catalysis in OER/ORR. A possible origin high OER activity unique surface structure through corner-shared planar MnO4 octahedral MnO6 units to promote direct OO bond formations.

Insertion of a symmetric metal complex, [CrIII(5,5′-tBu-salophen)]+ (H2salophen=N,N′-bis(salicylidene)-1,2-phenylenediamine), into the active site apomyoglobin is demonstrated (see picture). The ion and ligand structure are very important factors that influence binding affinity complex with myoglobin (Mb) cavity. Semisynthetic metalloenzymes can catalyze enantioselective sulfoxidation by using chiral protein

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA High-Valent Nonheme Iron Intermediate. Structure and Properties of [Fe2(.mu.-O)2(5-Me-TPA)2](ClO4)3Yanhong Dong, Hiroshi Fujii, Michael P. Hendrich, Randolph A. Leising, Gaofeng Pan, Clayton R. Randall, Elizabeth C. Wilkinson, Yan Zang, Lawrence Que Jr., Cite this: J. Am. Chem. Soc. 1995, 117, 10, 2778–2792Publication Date (Print):March 1, 1995Publication History Published online1 May 2002Published inissue 1 March...

Ligand radicals from salen complexes are unique mixed-valence compounds in which a phenoxyl radical is electronically linked to remote phenolate via neighboring redox-active metal ion, providing an opportunity study electron transfer mediated by ion as bridge. We herein synthesize one-electron-oxidized products diverse manganese(III) the locus of oxidation shown be ligand-centered, not metal-centered, affording manganese(III)–phenoxyl species. The key point present unambiguous assignment...

Ever-proposed descriptors of catalytic activity for the oxygen evolution reaction (OER) were systematically investigated. A wide variety stoichiometric perovskite oxides ABO3 (A = Ca, Sr, Y, La; B Ti, V, Cr, Mn, Fe, Co, Ni, Cu) examined as OER catalysts. The simplest descriptor, eg, electron number transition-metal ions at B-site, was not applicable overpotentials (η) compounds tested in this study. Another 2p band center relative to Fermi energy (ε2p), necessarily adequate most part oxides....

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffects of the electron-withdrawing power substituents on electronic structure and reactivity in oxoiron(IV) porphyrin .pi.-cation radical complexesHiroshi FujiiCite this: J. Am. Chem. Soc. 1993, 115, 11, 4641–4648Publication Date (Print):June 1, 1993Publication History Published online1 May 2002Published inissue 1 June 1993https://pubs.acs.org/doi/10.1021/ja00064a027https://doi.org/10.1021/ja00064a027research-articleACS PublicationsRequest reuse...

Heme oxygenase (HO) catalyzes the O2- and NADPH-cytochrome P450 reductase-dependent conversion of heme to biliverdin, Fe, CO through a process in which participates both as prosthetic group substrate. In present study, we have generated detailed reaction cycle for first monooxygenation step HO catalysis, α-meso-hydroxyheme. We employed EPR (using 16O2 17O2) 1H, 14N ENDOR spectroscopies characterize intermediates by 77 K radiolytic cryoreduction subsequent annealing wild-type oxy-HO D140A, F...

Stability theorem is presented for large amplitude singularly perturbed solutions (SPS) of reactiondiffusion systems on a finite interval. Spectral analysis shows that there exists unique real critical eigenvalue $\lambda _c (\varepsilon )$ which behaves like ) \simeq \tau \varepsilon $ as $\varepsilon \downarrow 0$, where small parameter contained in the system. All other noncritical eigenvalues have strictly negative parts independent $. The singular limit problem §2 plays key role to...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTClathrate formation and molecular recognition by novel chalcogen-cyano interactions in tetracyanoquinodimethanes fused with thiadiazole selenadiazole ringsTakanori Suzuki, Hiroshi Fujii, Yoshiro Yamashita, Chizuko Kabuto, Shoji Tanaka, Masako Harasawa, Toshio Mukai, Tsutomu MiyashiCite this: J. Am. Chem. Soc. 1992, 114, 8, 3034–3043Publication Date (Print):April 1, 1992Publication History Published online1 May 2002Published inissue 1 April...

To study the effect of axial ligands on electronic structure and reactivity compound I peroxidases catalases, oxoiron(IV) porphyrin π-cation radical complexes with imidazole, 2-methylimidazole, 4(5)-methylimidazole, 3-fluoro-4-nitrophenolate as were prepared by ozone oxidation iron(III) 5,10,15,20-tetramesitylporphyrin (TMP) 2,7,12,17-tetramethyl-3,8,13,18-tetramesitylporphyrin (TMTMP). These fully characterized absorption, 1H, 2H, 19F NMR, electron paramagnetic resonance (EPR), electrospray...

The proximal heme axial ligand plays an important role in tuning the reactivity of oxoiron(IV) porphyrin π-cation radical species (compound I) enzymatic and catalytic oxygenation reactions. To reveal essence effect on reactivity, we investigated it from a thermodynamic viewpoint. Compound I model complexes, (TMP(+•))Fe(IV)O(L) (where TMP is 5,10,15,20-tetramesitylporphyrin TMP(+•) its radical), can be provided with altered by changing identity ligand, but not correlated spectroscopic data...

Hydroxylation reactions of aromatic rings are key in various biological and chemical processes. In spite their significance, no consensus mechanism has been established. Here we performed Marcus plot analysis for hydroxylation with oxoiron(IV) porphyrin π-cation radical complexes (compound I). Although many recent studies support the involving direct electrophilic attack compound I, slopes plots indicate a significant contribution an electron transfer process rate-limiting step, leading us...

Heme oxygenase (HO) catalyzes the oxygen-dependent degradation of heme to biliverdinIXα, CO, and free iron ion via three sequential monooxygenase reactions. Although distinct active-site structure HO from cytochrome P450 families suggests unique distal protein machinery activate molecular oxygen, mechanism key amino acid for oxygen activation have not been clear. To investigate functionality highly conserved polar acids in helix HO-1, we prepared alanine mutants: T135A, R136A, D140A, S142A,...

Heme oxygenase is a central enzyme of heme degradation and associated carbon monoxide biosynthesis. We have prepared the alpha-hydroxyheme-heme complex, which first intermediate in catalytic reaction. The active site structure complex was examined by optical absorption, EPR, resonance Raman spectroscopies. In ferric form iron five coordinate high spin alpha-hydroxyheme group assumes an oxophlorin where alpha-meso hydroxy deprotonated. ferrous form, alpha-hydroxy protonated consequently...

It is shown that an iron(III) meso-N-substituted corrole (TBP(8)Cz)Fe(III) (1) (TBP(8)Cz = octakis(4-tert-butylphenyl)corrolazinato), a potent catalyst for the oxidation of alkenes in presence pentaflouroiodosylbenzene (C(6)F(5)IO) as oxidant. In case cyclohexene, complex 1 performs on par with one best porphyrin catalysts ((TPPF(20))FeCl), exhibiting rapid turnover and high selectivity epoxide (CzFe(III)/C(6)F(5)IO/cyclohexene (1:100:1000) CH(2)Cl(2)/CH(3)OH (3:1 v:v) gives 33 turnovers <2...

In order to reveal structure–reactivity relationships for the high catalytic activity of epoxidation catalyst Mn(salen), transient intermediates are investigated. Steric hindrance incorporated salen ligand enables highly selective generation three related intermediates, O═MnIV(salen), HO−MnIV(salen), and H2O−MnIII(salen+•), each which is thoroughly characterized using various spectroscopic techniques including UV–vis, electron paramagnetic resonance, resonance Raman, electrospray ionization...

The first direct observation of the transient spin-state in a disordered magnetic system with time-resolved XAFS is reported. By observing evolution Fe(II) 1s-3d transition, spin crossover transition from (1)A(1) low state to (5)T(2) high has been directly observed on picosecond time scale. Moreover, allows for investigation variations electronic and molecular structure. This unique experimental technique probes excited states involved ultrafast photoinduced reactions systems.

To gain an understanding of oxidation reactions by MnIII(salen), a reaction MnIII(salen) with m-chloroperoxybenzoic acid in the absence substrate is investigated. UV−vis, perpendicular- and parallel-mode electron paramagnetic resonance, X-ray absorption spectroscopy show that resulting solution contains MnIV(salen)(O) as major product MnIV(salen)(OH) minor product. readily reacts 4-H-2,6-tert-Bu2C6H2OH (homolytic bond dissociation energy OH bond, BDEOH = 82.8 kcal mol−1),...

The Co(salen)(X) complex, where salen is chiral N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine and X an external axial ligand, has been widely utilized as a versatile catalyst. complex stable solid that conventionally described CoIII(salen)(X) complex. Recent theoretical calculations raised new proposal the Co(salen)(H2O)(SbF6) contains appreciable contribution from CoII(salen•+) electronic structure (Kochem, A.; Kanso, H.; Baptiste, B.; Arora, Philouze, C.; Jarjayes, O.;...

F. A. Bell, R. Crellin, H. Fujii and Ledwith, J. Chem. Soc. D, 1969, 251 DOI: 10.1039/C29690000251