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651.
Catalytic activity of gold-platinum, gold-palladium, and platinum-palladium dendrimer nanocomposites for scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals was investigated. The gold-platinum and gold-palladium dendrimer nanocomposites were prepared via simultaneous reduction by sodium borohydride in the presence of poly(amidoamine) (PAMAM) dendrimers with amine or carboxyl terminal groups. The particles were not mixtures of monometallic particles but alloyed bimetallic particles. Bimetallic particles exhibited higher catalytic activity than monometallic ones. 相似文献
652.
Three novel diterpenes were isolated from cultures of an unidentified marine-derived fungus. The structures of the compounds, phomactin I (1), 13-epi-phomactin I (2), and phomactin J (3) were determined by spectroscopic and X-ray crystallographic methods. 相似文献
653.
Toshiki Nishiura Takehiro Ohta Takashi Ogura Jun Nakazawa Masaya Okamura Shiro Hikichi 《Molecules (Basel, Switzerland)》2022,27(19)
Conversion from superoxide (O2−) to hydroperoxide (OOH−) on the metal center of oxygenases and oxidases is recognized to be a key step to generating an active species for substrate oxidation. In this study, reactivity of cobalt(III)-superoxido complexes supported by facially-capping tridentate tris(3,5-dimethyl-4-X-pyrazolyl)hydroborate ([HB(pzMe2,X)3]−; TpMe2,X) and bidentate bis(1-methyl-imidazolyl)methylborate ([B(ImN-Me)2Me(Y)]−; LY) ligands toward H-atom donating reagent (2-hydroxy-2-azaadamantane; AZADOL) has been explored. The oxygenation of the cobalt(II) precursors give the corresponding cobalt(III)-superoxido complexes, and the following reaction with AZADOL yield the hydroperoxido species as has been characterized by spectroscopy (UV-vis, resonance Raman, EPR). The reaction of the cobalt(III)-superoxido species and a reducing reagent ([CoII(C5H5)2]; cobaltocene) with proton (trifluoroacetic acid; TFA) also yields the corresponding cobalt(III)-hydroperoxido species. Kinetic analyses of the formation rates of the cobalt(III)-hydroperoxido complexes reveal that second-order rate constants depend on the structural and electronic properties of the cobalt-supporting chelating ligands. An electron-withdrawing ligand opposite to the superoxide accelerates the hydrogen atom transfer (HAT) reaction from AZADOL due to an increase in the electrophilicity of the superoxide ligand. Shielding the cobalt center by the alkyl group on the boron center of bis(imidazolyl)borate ligands hinders the approaching of AZADOL to the superoxide, although the steric effect is insignificant. 相似文献
654.
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656.
Yasuyuki Yamada Hiroaki Nakajima Chisa Kobayashi Yoshiaki Shuku Kunio Awaga Shigehisa Akine Kentaro Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2023,29(1):e202203272
A C4h symmetrically substituted phthalocyanine, 1,8,15,22-tertrakis(2,4-dimethylpent-3-oxy)phthalocyanine (H2TdMPPc), was used to synthesize Tb3+-phthalocyanine double-decker complexes ([Tb(TdMPPc)2]s). Because H2TdMPPc has C4h symmetry, S,S, R,R, and meso isomers of [Tb(TdMPPc)2] were obtained depending on the difference in the direction of the coordination plane of two C4h-type phthalocyanines with respect to a central Tb3+ ion. We investigated the physical properties of these [Tb(TdMPPc)2] isomers, including their single-ion magnetic properties, and found that the spin-reversal energy barrier (Ueff) of the meso isomer was apparently higher than that of the enantiomers. Detailed crystal structural analyses indicated that the meso isomer has a more symmetrical structure than do the enantiomers, thereby suggesting that the higher Ueff of the meso isomer originated from the more highly symmetrical structure. 相似文献
657.