An “experimental” valence state of metal complexes is sometime different from the “formal” oxidation state, especially in the species having redox active ligands. This difference can be seen in biological system, ...An “experimental” valence state of metal complexes is sometime different from the “formal” oxidation state, especially in the species having redox active ligands. This difference can be seen in biological system, such as iron(IV)-porphyrin π-cation radical in some heme proteins and copper(II)-phenoxyl radical in galactose oxidase (GO). Although structural characterizations of these species by X-ray diffraction methods have been rare due to their stability, some artificial metal-phenoxyl radical complexes have been synthesized and successfully characterized by X-ray crystal structure. In this review, syntheses and X-ray crystal structures of the one-electron oxidized metal-phenolate complexes, metal- phenoxyl radical, and high-valent metal phenolate species are discussed.展开更多
Water oxidation is one of the most important reactions in natural and artificial energy conversion schemes.In nature,solar energy is converted to chemical energy via water oxidation at the oxygen-evolving center of ph...Water oxidation is one of the most important reactions in natural and artificial energy conversion schemes.In nature,solar energy is converted to chemical energy via water oxidation at the oxygen-evolving center of photosystem II to generate dioxygen,protons,and electrons.In artificial energy schemes,water oxidation is one of the half reactions of water splitting,which is an appealing strategy for energy conversion via photocatalytic,electrocatalytic,or photoelectrocatalytic processes.Because it is thermodynamically unfavorable and kinetically slow,water oxidation is the bottleneck for achieving large-scale water splitting.Thus,developing highly efficient water oxidation catalysts has attracted the interests of researchers in the past decades.The formation of O-O bonds is typically the rate-determining step of the water oxidation catalytic cycle.Therefore,better understanding this key step is critical for the rational design of more efficient catalysts.This review focuses on elucidating the evolution of metal-oxygen species during transition metal-catalyzed water oxidation,and more importantly,on discussing the feasible O-O bond formation mechanisms during the oxygen evolution reaction over synthetic molecular catalysts.展开更多
ZrO3 and HfO3 molecules were prepared via reactions of metal monoxides with dioxygen in solid argon and were characterized using matrix isolation infrared absorption spectroscopy as well as theoretical calculations. U...ZrO3 and HfO3 molecules were prepared via reactions of metal monoxides with dioxygen in solid argon and were characterized using matrix isolation infrared absorption spectroscopy as well as theoretical calculations. Unlike the titanium monoxide molecule, which reacted spontaneously with dioxygen to form TiO3, the ZrO and HfO molecules reacted with dioxygen to give the ZrO3 and HfO3 molecules only under visible light irradiation. Density functional calculations predicted that both the ZrO3 and HfO3 molecules possess a closed-shell singlet ground state with a non-planar C8 geometry, in which the side-on coordinated O2 falls into the peroxide category.展开更多
In this review, we summarize our recent results on matrix isolation infrared spectroscopic studies and theoretical investigations of noble gas-transition metal oxide complexes. The results show that some transition me...In this review, we summarize our recent results on matrix isolation infrared spectroscopic studies and theoretical investigations of noble gas-transition metal oxide complexes. The results show that some transition metal oxide species trapped in solid noble gas matrices are chemically coordinated by one or multiple noble gas atoms forming noble gas complexes and, hence, cannot be regarded as isolated species. Noble gas coordination alters the vibrational frequencies as well as the geometric and electronic structures of transition metal oxide species trapped in solid noble gas matrixes. The interactions between noble gas atoms and transition metal oxides involve ion-induced dipole interactions as well as chemical bonding interactions. Periodic trends in the bonding in these noble gas-transition metal complexes are discussed.展开更多
Salicylhydroxamic acid（SHA） was covalently grafted onto chloromethylated crosslinked polystyrene spheres（CMCPS） by the Friedel-Crafts alkylation reaction. The amount of SHA on CPS was found to be mainly dependent ...Salicylhydroxamic acid（SHA） was covalently grafted onto chloromethylated crosslinked polystyrene spheres（CMCPS） by the Friedel-Crafts alkylation reaction. The amount of SHA on CPS was found to be mainly dependent on the amount of Lewis acid（SnCl4） used and the reaction temperature. Under optimized conditions, the amount of SHA attached to CPS could reach up to 0.43 g/g CPS. Transition metal ions[Co（II）, Cu（II）, Fe（III） or Mn（II）] were then introduced into the resulting SHA-functionalized microspheres（SHA/CPS） through SHA-metal ion chelation. The obtained microspheres MSHA/CPS were explored as biomimetic catalysts for the aerobic oxidation of ethylbenzene（EB） to ethylbenzene hydroperoxide（EBHP）. Among the four supported metal catalysts, FeSHA/CPS showed the highest catalytic activity and good reusability, indicating its great potential as an effective heterogeneous catalyst for the aerobic oxidation of hydrocarbons under mild conditions.展开更多
文摘An “experimental” valence state of metal complexes is sometime different from the “formal” oxidation state, especially in the species having redox active ligands. This difference can be seen in biological system, such as iron(IV)-porphyrin π-cation radical in some heme proteins and copper(II)-phenoxyl radical in galactose oxidase (GO). Although structural characterizations of these species by X-ray diffraction methods have been rare due to their stability, some artificial metal-phenoxyl radical complexes have been synthesized and successfully characterized by X-ray crystal structure. In this review, syntheses and X-ray crystal structures of the one-electron oxidized metal-phenolate complexes, metal- phenoxyl radical, and high-valent metal phenolate species are discussed.
文摘Water oxidation is one of the most important reactions in natural and artificial energy conversion schemes.In nature,solar energy is converted to chemical energy via water oxidation at the oxygen-evolving center of photosystem II to generate dioxygen,protons,and electrons.In artificial energy schemes,water oxidation is one of the half reactions of water splitting,which is an appealing strategy for energy conversion via photocatalytic,electrocatalytic,or photoelectrocatalytic processes.Because it is thermodynamically unfavorable and kinetically slow,water oxidation is the bottleneck for achieving large-scale water splitting.Thus,developing highly efficient water oxidation catalysts has attracted the interests of researchers in the past decades.The formation of O-O bonds is typically the rate-determining step of the water oxidation catalytic cycle.Therefore,better understanding this key step is critical for the rational design of more efficient catalysts.This review focuses on elucidating the evolution of metal-oxygen species during transition metal-catalyzed water oxidation,and more importantly,on discussing the feasible O-O bond formation mechanisms during the oxygen evolution reaction over synthetic molecular catalysts.
基金Ⅴ. ACKNOWLEDGMENTS This work was supported by the National Basic Research Program of China （No.2007CB815203） and the National Natural Science Foundation of China （No.20773030）.
文摘ZrO3 and HfO3 molecules were prepared via reactions of metal monoxides with dioxygen in solid argon and were characterized using matrix isolation infrared absorption spectroscopy as well as theoretical calculations. Unlike the titanium monoxide molecule, which reacted spontaneously with dioxygen to form TiO3, the ZrO and HfO molecules reacted with dioxygen to give the ZrO3 and HfO3 molecules only under visible light irradiation. Density functional calculations predicted that both the ZrO3 and HfO3 molecules possess a closed-shell singlet ground state with a non-planar C8 geometry, in which the side-on coordinated O2 falls into the peroxide category.
基金supported by the National Basic Research Program of China (Grant No. 2007CB815203)the National Natural Science Foundation of China (Grant Nos. 20773030 and 20803066)
文摘In this review, we summarize our recent results on matrix isolation infrared spectroscopic studies and theoretical investigations of noble gas-transition metal oxide complexes. The results show that some transition metal oxide species trapped in solid noble gas matrices are chemically coordinated by one or multiple noble gas atoms forming noble gas complexes and, hence, cannot be regarded as isolated species. Noble gas coordination alters the vibrational frequencies as well as the geometric and electronic structures of transition metal oxide species trapped in solid noble gas matrixes. The interactions between noble gas atoms and transition metal oxides involve ion-induced dipole interactions as well as chemical bonding interactions. Periodic trends in the bonding in these noble gas-transition metal complexes are discussed.
基金Supported by the National Young Scientists Fund of China（No.21307116）, the Natural Science Foundation of Shanxi Province, China（No.2014011017-5）, the Project for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi Province, China（No.201504） and the Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province, China（No.20140828）.
文摘Salicylhydroxamic acid（SHA） was covalently grafted onto chloromethylated crosslinked polystyrene spheres（CMCPS） by the Friedel-Crafts alkylation reaction. The amount of SHA on CPS was found to be mainly dependent on the amount of Lewis acid（SnCl4） used and the reaction temperature. Under optimized conditions, the amount of SHA attached to CPS could reach up to 0.43 g/g CPS. Transition metal ions[Co（II）, Cu（II）, Fe（III） or Mn（II）] were then introduced into the resulting SHA-functionalized microspheres（SHA/CPS） through SHA-metal ion chelation. The obtained microspheres MSHA/CPS were explored as biomimetic catalysts for the aerobic oxidation of ethylbenzene（EB） to ethylbenzene hydroperoxide（EBHP）. Among the four supported metal catalysts, FeSHA/CPS showed the highest catalytic activity and good reusability, indicating its great potential as an effective heterogeneous catalyst for the aerobic oxidation of hydrocarbons under mild conditions.
