Chemical Hazard of Acid Water Drainage from Mudstone Rock Muck Disposal Site

( Takehiro Ohta ) 대한지질공학회 2007 국제학술발표회 논문집 Vol.2007 No.-

Structure and Reactivity of a Mononuclear Nonheme Manganese(III)-Iodosylarene Complex

Jeong, Donghyun,Ohta, Takehiro,Cho, Jaeheung American Chemical Society 2018 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.140 No.47

<P>Transition metal-iodosylarene complexes have been proposed to be key intermediates in the catalytic cycles of metal catalysts with iodosylarene. We report the first X-ray crystal structure and spectroscopic characterization of a mononuclear nonheme manganese(III)-iodosylarene complex with a tetradentate macrocyclic ligand, [Mn<SUP>III</SUP>(TBDAP)(OIPh)(OH)]<SUP>2+</SUP> (<B>2</B>). The manganese(III)-iodosylarene complex is capable of conducting various oxidation reactions with organic substrates, such as C-H bond activation, sulfoxidation and epoxidation. Kinetic studies including isotope labeling experiments and Hammett correlation demonstrate the electrophilic character on the Mn-iodosylarene adduct. This novel intermediate would be prominently valuable for expanding the chemistry of transition metal catalysts.</P> [FIG OMISSION]</BR>

Distinct Reactivity of a Mononuclear Peroxocobalt(III) Species toward Activation of Nitriles

Noh, Hyeonju,Jeong, Donghyun,Ohta, Takehiro,Ogura, Takashi,Valentine, Joan Selverstone,Cho, Jaeheung American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.32

<P>A mononuclear side-on peroxocobalt(III) complex with a tetradentate macrocyclic ligand, [Co-III(TBDAP)(O-2)](+) (1), shows a novel and facile mode of dioxygenase-like reactivity with nitriles (R-C N; R = Me, Et, and Ph) to produce the corresponding mononuclear hydroximatocobalt(III) complexes, [CoIII(TBDAP)(R-C(=NO)O)](+), in which the nitrile moiety is oxidized by two oxygen atoms of the peroxo group. The overall reaction proceeds in one-pot under ambient conditions (ca. 1 h, 40 degrees C). O-18-Labeling experiments confirm that both oxygen atoms are derived from the peroxo ligand. The structures of all products, hydroximatocobalt(III) complexes, were confirmed by X-ray crystallography and various spectroscopic techniques. Kinetic studies including the Hammett analysis and isotope labeling experiments suggest that the mechanistic mode of 1 for activation of nitriles occurs-via a concerted mechanism. This novel reaction would be significantly valuable for expanding the chemistry for nitrile activation and utilization.</P>

A simplified PCR assay for fast and easy mycoplasma mastitis screening in dairy cattle

Hidetoshi Higuchi,Hidetomo Iwano,Kazuhiro Kawai,Takehiro Ohta,Tetsu Obayashi,Kazuhiko Hirose,Nobuhiko Ito,Hiroshi Yokota,Yutaka Tamura,Hajime Nagahata 대한수의학회 2011 Journal of Veterinary Science Vol.12 No.2

A simplified polymerase chain reaction (PCR) assay was developed for fast and easy screening of mycoplasma mastitis in dairy cattle. Species of major mycoplasma strains [Mycoplasma (M.) bovis, M. arginini, M. bovigenitalium, M. californicum, M. bovirhinis, M. alkalescens and M. canadense] in cultured milk samples were detected by this simplified PCR-based method as well as a standard PCR technique. The minimum concentration limit for detecting mycoplasma by the simplified PCR was estimated to be about 2.5 × 10^3 cfu/mL and was similar to that of the standard PCR. We compared the specificity and sensitivity of the simplified PCR to those of a culture method. Out of 1,685 milk samples cultured in mycoplasma broth, the simplified PCR detected Mycoplasma DNA in 152 that were also positive according to the culture assay. The sensitivity and specificity of the simplified PCR were 98.7% and 99.7%, respectively, for detecting mycoplasma in those cultures. The results obtained by the simplified PCR were consistent with ones from standard PCR. This newly developed simplified PCR, which does not require DNA purification, can analyze about 300 cultured samples within 3 h. The results from our study suggest that the simplified PCR can be used for mycoplasma mastitis screening in large-scale dairy farms.

Achieving One-Electron Oxidation of a Mononuclear Nonheme Iron(V)-Imido Complex

Hong, Seungwoo,Lu, Xiaoyan,Lee, Yong-Min,Seo, Mi Sook,Ohta, Takehiro,Ogura, Takashi,Clé,mancey, Martin,Maldivi, Pascale,Latour, Jean-Marc,Sarangi, Ritimukta,Nam, Wonwoo American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.41

<P>A mononuclear nonheme iron(V)-imido complex bearing a tetraamido macrocyclic ligand (TAML), [Fe<SUP>V</SUP>(NTs)(TAML)]<SUP>−</SUP> (<B>1</B>), was oxidized by one-electron oxidants, affording formation of an iron(V)-imido TAML cation radical species, [Fe<SUP>V</SUP>(NTs)(TAML<SUP>+•</SUP>)] (<B>2</B>); <B>2</B> is a diamagnetic (<I>S</I> = 0) complex, resulting from the antiferromagnetic coupling of the low-spin iron(V) ion (<I>S</I> = 1/2) with the one-electron oxidized ligand (TAML<SUP>+•</SUP>). <B>2</B> is a competent oxidant in C–H bond functionalization and nitrene transfer reaction, showing that the reactivity of <B>2</B> is greater than that of <B>1</B>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2017/jacsat.2017.139.issue-41/jacs.7b08161/production/images/medium/ja-2017-081612_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja7b08161'>ACS Electronic Supporting Info</A></P>

Dioxygen Activation and O-O Bond Formation Reactions by Manganese Corroles

Guo, Mian,Lee, Yong-Min,Gupta, Ranjana,Seo, Mi Sook,Ohta, Takehiro,Wang, Hua-Hua,Liu, Hai-Yang,Dhuri, Sunder N.,Sarangi, Ritimukta,Fukuzumi, Shunichi,Nam, Wonwoo American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.44

<P>Activation of dioxygen (O-2) in enzymatic and biomimetic reactions has been intensively investigated over the past several decades. More recently, O-O bond formation, which is the reverse of the O-2-activation reaction, has been the focus of current research. Herein, we report the O-2-activation and O-O bond formation reactions by manganese corrole complexes. In the O-2-activation reaction, Mn(V)-oxo and Mn(IV)-peroxo intermediates were formed when Mn(III) corroles were exposed to O-2 in the presence of base (e.g., OH-) and hydrogen atom (H atom) donor (e.g., THE or cyclic olefins); the O-2-activation reaction did not occur in the absence of base and H atom donor. Moreover, formation of the Mn(V)-oxo and Mn(IV)-peroxo species was dependent on the amounts of base present in the reaction solution. The role of the base was proposed to lower the oxidation potential of the Mn(III) corroles, thereby facilitating the binding of O-2 and forming a Mn(IV)-superoxo species. The putative Mn(IV)-superoxo species was then converted to the corresponding Mn(IV)-hydroperoxo species by abstracting a H atom from H atom donor, followed by the O-O bond cleavage of the putative Mn(IV)-hydroperoxo species to form a Mn(V)-oxo species. We have also shown that addition of hydroxide ion to the Mn(V)-oxo species afforded the Mn(IV)-peroxo species via O-O bond formation and the resulting Mn(IV)-peroxo species reverted to the Mn(V)-oxo species upon addition of proton, indicating that the O-O bond formation and cleavage reactions between the Mn(V)-oxo and Mn(IV)-peroxo complexes are reversible. The present study reports the first example of using the same manganese complex in both O-2-activation and O-O bond formation reactions.</P>

Mn(III)-Iodosylarene Porphyrins as an Active Oxidant in Oxidation Reactions: Synthesis, Characterization, and Reactivity Studies

Guo, Mian,Lee, Yong-Min,Seo, Mi Sook,Kwon, Yong-Ju,Li, Xiao-Xi,Ohta, Takehiro,Kim, Won-Suk,Sarangi, Ritimukta,Fukuzumi, Shunichi,Nam, Wonwoo American Chemical Society 2018 Inorganic Chemistry Vol.57 No.16

<P>Mn(III)-iodosylarene porphyrin adducts, [Mn(III)(ArIO)(Porp)]<SUP>+</SUP>, were synthesized by reacting electron-deficient Mn(III) porphyrin complexes with iodosylarene (ArIO) at −60 °C and characterized using various spectroscopic methods. The [Mn(III)(ArIO)(Porp)]<SUP>+</SUP> species were then investigated in the epoxidation of olefins under stoichiometric conditions. In the epoxidation of olefins by the Mn(III)-iodosylarene porphyrin species, epoxide was formed as the sole product with high chemoselectivities and stereoselectivities. For example, cyclohexene oxide was formed exclusively with trace amounts of allylic oxidation products; <I>cis</I>- and <I>trans</I>-stilbenes were oxidized to the corresponding <I>cis</I>- and <I>trans</I>-stilbene oxides, respectively. In the catalytic epoxidation of cyclohexene by an electron-deficient Mn(III) porphyrin complex and <SUP>s</SUP>PhIO at low temperature (e.g., −60 °C), the Mn(III)-iodosylarene porphyrin species was evidenced as the active oxidant that effects the olefin epoxidation to give epoxide as the product. However, at high temperature (e.g., 0 °C) or in the case of using an electron-rich manganese(III) porphyrin catalyst, allylic oxidation products, along with cyclohexene oxide, were yielded, indicating that the active oxidant(s) was not the Mn(III)-iodosylarene adduct but probably high-valent Mn-oxo species in the catalytic reactions. We also report the conversion of the Mn(III)-iodosylarene porphyrins to high-valent Mn-oxo porphyrins under various conditions, such as at high temperature, with electron-rich porphyrin ligand, and in the presence of base (OH<SUP>-</SUP>). The present study reports the first example of spectroscopically well-characterized Mn(III)-iodosylarene porphyrin species being an active oxidant in the stoichiometric and catalytic oxidation reactions. Other aspects, such as one oxidant versus multiple oxidants debate, also were discussed.</P><P>Mn(III)-iodosylarene porphyrin adducts, [Mn(III)(ArIO)(Porp)]<SUP>+</SUP>, were synthesized by reacting electron-deficient Mn(III) porphyrin complexes with iodosylarene (ArIO) and characterized using various spectroscopic methods. In the epoxidation of olefins by the Mn(III)-iodosylarene porphyrin species, epoxide was formed as the sole product with high chemoselectivities and stereoselectivities. The present study reports the first example of spectroscopically well-characterized Mn(III)-iodosylarene porphyrin species being an active oxidant in the stoichiometric and catalytic oxidation reactions.</P> [FIG OMISSION]</BR>