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Author

Manabu Fujiwara

Bio: Manabu Fujiwara is an academic researcher from Ryukoku University. The author has contributed to research in topics: Schiff base & Copper. The author has an hindex of 14, co-authored 40 publications receiving 501 citations.
Topics: Schiff base, Copper, Manganese, Acetylacetone, Nickel

Papers
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Journal ArticleDOI
TL;DR: In this paper, a cyclic tetranuclear manganese(III) complexes with Schiff base ligands, N,N′-substituted-salicylidene-1,3-diaminobenzene (X = H, 5-Br), X-salmphenH2, MnIII4(X-Salmphen)6 have been prepared and characterized by spectroscopies, magnetic susceptibility, electrochemical measurements and X-ray crystallography.

69 citations

Journal ArticleDOI
TL;DR: In this paper, a series of tetradentate Schiff base base ligands and a tetradate manganese (TMS) was used to construct di-μ-oxo dimanganese (IV) complexes.

45 citations

Journal ArticleDOI
TL;DR: X-ray structure analysis revealed that four types of novel manganese complexes, MnIV(N-EtO-sal)2, MnIII (N-PhO-Sal), MnIII(NPhO)-sal), [MnIV(5,6-Benzo-L)2(μ-O)]2 and MnIII-L-4-Me)3 have been found to be obtained by the reactions of KMnO4 with various tridentate Schiff base ligands in dry MeCN.

39 citations

Journal ArticleDOI
TL;DR: In this paper, the shift, asymmetry and spin-orbit splitting energy were extracted from the measured spectra of a double-crystal x-ray fluorescence spectrometer and the asymmetric Kα lineshape was deconvoluted by Lorentzian functions.
Abstract: Nickel K-L (Kα) x-ray fluorescence spectra of 32 kinds of materials containing nickel [NiF 2 , NiSO 4 , Ni(CO 3 ) 2 , Ni(OH) 2 , Ni 2 O 3 , NiTiO 3 , NiO, NiFe 2 O 4 , NiCl 2 , NiBr 2 , NiI 2 , LiNiO 2 , NiS, NiTe, Ni 3 P, metal, LaNi 5 , Ni 2 P, NiCr, Ni 2 Si, NiB, NiSi 2 , acetylacetonate, K 2 Ni(CN) 4 , and some nickel complexes] were measured using a double-crystal x-ray fluorescence spectrometer. The shift, asymmetry and spin-orbit splitting energy were extracted from the measured spectra. The asymmetric Kα lineshape was deconvoluted by Lorentzian functions. It is demonstrated that the chemical state of nickel in an unknown material can be analyzed by the use of these parameters.

36 citations

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TL;DR: The trinuclear manganese(II) complexes, [MnII3(OAc)4(pap)2(H2O)2] and [MmII3OAc]4(5-Cl-pap), were prepared by the reaction of tridentate Schiff base ligands XpapH (X=H, Cl), [N-2pyridiylmethylidene-2-hydroxy-5-substituted-phenylamine], and MnII(OAC)2·2

32 citations


Cited by
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TL;DR: In this paper, the authors have synthesized and characterized rare earth-based europium organic complexes Eu(TTA)3Phen, Eu (x)Y(1−x)(TTA), Eu0.5Y 0.5Tb0.
Abstract: This paper reflects the achievements and the challenges ahead in the field of organic light emitting diodes (OLEDs). The primary intention of this paper is to study different organic materials synthesized so far and the OLEDs fabricated for solid-state lighting. After deep review of literature we have synthesized and characterized rare earth based europium organic complexes Eu(TTA)3Phen, Eu(x)Y(1−x)(TTA)3Phen, and Eu(x)Tb(1−x)(TTA)3Phen, where x = 0.4 and 0.5 by solution technique maintaining stoichiometric ratio. Blended films of pure and doped Eu complexes that are molecularly doped into polymer resins namely polymethylmethacrylate (PMMA) and polystyrene (PS) are prepared according to weight percentage. Concentration effect on absorption and emission spectra of the blended films was studied for different weight percentages (10, 25, 50, 60%). All the complexes doped in PMMA showed an excellent transparency of 90–97% while the complexes doped in polystyrene showed a transparency of 85–90%, bit less than in PMMA. Energy gap of the synthesized complexes have been determined in PMMA and PS. Considering the facts that these complexes have good solubility in most of the organic solvents, the absorption spectra of Eu(TTA)3Phen, Eu0.5Y0.5(TTA)3Phen and Eu0.5Tb0.5(TTA)3Phen complexes are studied, and OLED devices having the structure ITO/m-MTDATA/α-NPD/TPBi:Eu(x)Y(1−x)(TTA)3Phen/Alq3/LiF:Al (where x = 0.4, 0.5) were fabricated and characterized. Significant red emission was observed from fabricated OLED devices at 612 nm when operated in a range of 10–18 V. Thus the synthesized rare earth based organic complexes are the best suitable candidates for fabrication of red OLED devices. The extensive review on OLEDS concludes that our present lighting system can be replaced with white OLEDS, recently developed energy saving lighting technology.

538 citations

Journal ArticleDOI
TL;DR: A hybrid density functional theory has been utilized to put forward a triangular Mn moiety closely coupled by μ-oxo groups as a potential model for the WO site and another mechanism incorporating a “C-shaped” cluster has also been suggested recently.
Abstract: ion model is not a true H-abstracting process but rather a special case of proton-coupled electron transfer where reduction of YZ by the Mn4 cluster occurs with the proton emanating from solvent water. These two theories will now be described briefly. A hydrogen atom abstraction process by the YZ residue in conjunction with a dimer-of-dimers structural template has led to an interesting hypothesis wherein an O atom is proposed as a terminal ligand to Mn (see Figure 8 (top)).175,188 The Clion is proposed to migrate in S1 to S2 and S2 to S3 state transitions while YZ serves as the H atom abstractor and Ca2+ ion binds to Clin the lower S states. In another proposal two dinuclear Mn complexes perform diverse functions: one oxidizes H2O to peroxide while the other converts peroxide to water.16,189-191 The final O-O bond forming step in the S4 state is predicted to result from attack of the hydroxo group bound to Ca2+ to a strongly electrophilic MnVdO species. In a similar hypothesis, a Clbridging between a Mn and a Ca2+ is responsible for modulating the nucleophilic attack of the hydroxide ion.181,192 This was first predicted from mass spectrometric studies.176 The product of this step has been argued to be similar to the ferric hydroperoxide in oxyhemerythrin. Oxygen release is envisioned in a manner similar to that of oxyhemerythrin concomitant with reduction of Mn and protonation of μ-oxo bridges.192 On the basis of XAS and EPR data, another mechanism incorporating a “C-shaped” cluster has also been suggested recently involving one redox-active Mn per [Mn2(μ-O)2] dimeric moiety (see Figure 8 (bottom)).17,193,194 Here, the O-O bond is formed between an oxyl radical and a μ-oxo atom. A hybrid density functional theory has been utilized to put forward a triangular Mn moiety closely coupled by μ-oxo groups as a potential model for the WO site. The previously suggested oxyl radical mechanism14 has been reexamined in this work with an oxyl radical placed in a bridging fashion between two Mn atoms. Consistent with earlier studies, only one Mn is redox active in this model and the Ca2+ ion has been shown as playing the role of a bridging metal Manganese Clusters with Relevance to Photosystem II Chemical Reviews, 2004, Vol. 104, No. 9 3991

533 citations

Journal ArticleDOI
TL;DR: A detailed assessment of the chemistry of Mn oxides by considering how their bulk and nanoscale properties contribute to their effectiveness as water-oxidizing catalysts and the issue of Mn complexes decomposing to Mn oxide is provided.
Abstract: All cyanobacteria, algae, and plants use a similar water-oxidizing catalyst for water oxidation. This catalyst is housed in Photosystem II, a membrane-protein complex that functions as a light-driven water oxidase in oxygenic photosynthesis. Water oxidation is also an important reaction in artificial photosynthesis because it has the potential to provide cheap electrons from water for hydrogen production or for the reduction of carbon dioxide on an industrial scale. The water-oxidizing complex of Photosystem II is a Mn–Ca cluster that oxidizes water with a low overpotential and high turnover frequency number of up to 25–90 molecules of O2 released per second. In this Review, we discuss the atomic structure of the Mn–Ca cluster of the Photosystem II water-oxidizing complex from the viewpoint that the underlying mechanism can be informative when designing artificial water-oxidizing catalysts. This is followed by consideration of functional Mn-based model complexes for water oxidation and the issue of Mn com...

513 citations