IBA Treatment of Poplar Cuttings and Soil Composition Amendment for Improved Adaptability and Survival

Cho, Wonwoo,Chandra, Romika,Lee, Wi-young,Kang, Hoduck Institute of Forest Science 2020 Journal of Forest Science Vol.36 No.4

Poplar trees from the Salicaceae family over the years have been utilized for various reasons which include prevention of deforestation as well as phytoremediation. This study aims to determine the optimal pre-treatment and soil conditions required for propagation of poplar cuttings for increased initial adaptability and survival rate. Five poplar clones (Hanan, 110, 107, DN-34, 52-225) were selected for IBA, soil composition treatments on propagation. IBA pre-treatment of cuttings were utilized 0, 10, and 100 mg l-1 concentrations. Soil compositions were amended with TKS-2+perlite 2:1 (v:v) and sandy clay loam mixed with artificial soil. According to the greenhouse results 10 mg l-1 of IBA showed a significant increase in plant height whereas 100 mg l-1 inhibited plant growth except in clone 110. Soil composition severely affected root growth and hence overall growth of the clones. Sandy clay loam soil had poor to stunted growth compared to TKS-2+perlite.

Secure Communications With Asymptotically Gaussian Compressed Encryption

Cho, Wonwoo,Yu, Nam Yul IEEE Signal Processing Society 2018 IEEE signal processing letters Vol.25 No.1

<P>In this letter, we study the security of a cryptosystem over wireless channels that employs the asymptotically Gaussian compressed encryption. We investigate the indistinguishability and the energy sensitivity of the cryptosystem, where the total variation (TV) distance is examined as a statistical measure for the indistinguishability. To characterize the TV distance, we compute the Hellinger distance between probability distributions of ciphertexts, each of which can be modeled as a circularly symmetric complex Gaussian random vector with a constraint on plaintexts. Using the distance metrics, we show that the cryptosystem can be a promising option for secure wireless communications by guaranteeing the indistinguishability against an eavesdropper, as long as each plain text has constant energy.</P>

Mechanistic Insights into the C–H Bond Activation of Hydrocarbons by Chromium(IV) Oxo and Chromium(III) Superoxo Complexes

Cho, Kyung-Bin,Kang, Hyeona,Woo, Jaeyoung,Park, Young Jun,Seo, Mi Sook,Cho, Jaeheung,Nam, Wonwoo American Chemical Society 2014 Inorganic Chemistry Vol.53 No.1

<P>The mechanism of the C–H bond activation of hydrocarbons by a nonheme chromium(IV) oxo complex bearing an N-methylated tetraazamacrocyclic cyclam (TMC) ligand, [Cr<SUP>IV</SUP>(O)(TMC)(Cl)]<SUP>+</SUP> (<B>2</B>), has been investigated experimentally and theoretically. In experimental studies, reaction rates of <B>2</B> with substrates having weak C–H bonds were found to depend on the concentration and bond dissociation energies of the substrates. A large kinetic isotope effect value of 60 was determined in the oxidation of dihydroanthracene (DHA) and deuterated DHA by <B>2</B>. These results led us to propose that the C–H bond activation reaction occurs via a H-atom abstraction mechanism, in which H-atom abstraction of substrates by <B>2</B> is the rate-determining step. In addition, formation of a chromium(III) hydroxo complex, [Cr<SUP>III</SUP>(OH)(TMC)(Cl)]<SUP>+</SUP> (<B>3</B>), was observed as a decomposed product of <B>2</B> in the C–H bond activation reaction. The Cr<SUP>III</SUP>OH product was characterized unambiguously with various spectroscopic methods and X-ray crystallography. Density functional theory (DFT) calculations support the experimental observations that the C–H bond activation by <B>2</B> does not occur via the conventional H-atom-abstraction/oxygen-rebound mechanism and that <B>3</B> is the product formed in this C–H bond activation reaction. DFT calculations also propose that <B>2</B> may have some Cr<SUP>III</SUP>O<SUP>•–</SUP> character. The oxidizing power of <B>2</B> was then compared with that of a chromium(III) superoxo complex bearing the identical TMC ligand, [Cr<SUP>III</SUP>(O<SUB>2</SUB>)(TMC)(Cl)]<SUP>+</SUP> (<B>1</B>), in the C–H bond activation reaction. By performing reactions of <B>1</B> and <B>2</B> with substrates under identical conditions, we were able to demonstrate that the reactivity of <B>2</B> is slightly greater than that of <B>1</B>. DFT calculations again support this experimental observation, showing that the rate-limiting barrier for the reaction with <B>2</B> is slightly lower than that of <B>1</B>.</P><P>The C−H bond activation of hydrocarbons by nonheme chromium(IV) oxo and chromium(III) superhydroxo complexes, [Cr<SUP>IV</SUP>(O)(TMC)(Cl)]<SUP>+</SUP> and [Cr<SUP>III</SUP>(O<SUB>2</SUB>)(TMC)(Cl)]<SUP>+</SUP>, has been investigated experimentally and theoretically. The C−H bond activation by the chromium(IV) oxo complex does not occur via the conventional H-atom-abstraction/oxygen-rebound mechanism. The reactivity of the chromium(IV) oxo complex is slightly greater than that of the chromium(III) superoxo complex in the C−H bond activation reactions.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/inocaj/2014/inocaj.2014.53.issue-1/ic402831f/production/images/medium/ic-2013-02831f_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ic402831f'>ACS Electronic Supporting Info</A></P>

Theoretical predictions of a highly reactive non-heme Fe(<small>IV</small>)&z.dbd;O complex with a high-spin ground state

Cho, Kyung-Bin,Shaik, Sason,Nam, Wonwoo Royal Society of Chemistry 2010 Chemical communications Vol.46 No.25

<P>Computations show that a non-heme iron(<SMALL>IV</SMALL>)–oxo complex with a trigonal bipyramidal structure, [(Me<SUB>6</SUB>TREN)Fe<SUP>IV</SUP>&z.dbd;O]<SUP>2+</SUP>, has a quintet ground state and a low activation barrier for H-abstraction from cyclohexane, whereas its ruthenium analogue, [(Me<SUB>6</SUB>TREN)Ru<SUP>IV</SUP>&z.dbd;O]<SUP>2+</SUP>, has a triplet ground state and a high H-abstraction barrier.</P> <P>Graphic Abstract</P><P>A non-heme iron(<SMALL>IV</SMALL>)–oxo complex with a trigonal bipyramidal structure has a quintet ground state and a low activation barrier in the C–H bond activation of cyclohexane. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0cc00292e'> </P>

Structure and reactivity of a mononuclear non-haem iron(III)??peroxo complex

Cho, Jaeheung,Jeon, Sujin,Wilson, Samuel A.,Liu, Lei V.,Kang, Eun A.,Braymer, Joseph J.,Lim, Mi Hee,Hedman, Britt,Hodgson, Keith O.,Valentine, Joan Selverstone,Solomon, Edward I.,Nam, Wonwoo Nature Publishing Group, a division of Macmillan P 2011 Nature Vol.478 No.7370

Oxygen-containing mononuclear iron species??iron(iii)??peroxo, iron(iii)??hydroperoxo and iron(iv)??oxo??are key intermediates in the catalytic activation of dioxygen by iron-containing metalloenzymes. It has been difficult to generate synthetic analogues of these three active iron??oxygen species in identical host complexes, which is necessary to elucidate changes to the structure of the iron centre during catalysis and the factors that control their chemical reactivities with substrates. Here we report the high-resolution crystal structure of a mononuclear non-haem side-on iron(iii)??peroxo complex, [Fe(iii)(TMC)(OO)]<SUP>+</SUP>. We also report a series of chemical reactions in which this iron(iii)??peroxo complex is cleanly converted to the iron(iii)??hydroperoxo complex, [Fe(iii)(TMC)(OOH)]<SUP>2+</SUP>, via a short-lived intermediate on protonation. This iron(iii)??hydroperoxo complex then cleanly converts to the ferryl complex, [Fe(iv)(TMC)(O)]<SUP>2+</SUP>, via homolytic O??O bond cleavage of the iron(iii)??hydroperoxo species. All three of these iron species??the three most biologically relevant iron??oxygen intermediates??have been spectroscopically characterized; we note that they have been obtained using a simple macrocyclic ligand. We have performed relative reactivity studies on these three iron species which reveal that the iron(iii)??hydroperoxo complex is the most reactive of the three in the deformylation of aldehydes and that it has a similar reactivity to the iron(iv)??oxo complex in C??H bond activation of alkylaromatics. These reactivity results demonstrate that iron(iii)??hydroperoxo species are viable oxidants in both nucleophilic and electrophilic reactions by iron-containing enzymes.

A Chromium(III)–Superoxo Complex in Oxygen Atom Transfer Reactions as a Chemical Model of Cysteine Dioxygenase

Cho, Jaeheung,Woo, Jaeyoung,Nam, Wonwoo American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.27

<P>Metal–superoxo species are believed to play key roles in oxygenation reactions by metalloenzymes. One example is cysteine dioxygenase (CDO) that catalyzes the oxidation of cysteine with O<SUB>2</SUB>, and an iron(III)–superoxo species is proposed as an intermediate that effects the sulfoxidation reaction. We now report the first biomimetic example showing that a chromium(III)–superoxo complex bearing a macrocyclic TMC ligand, [Cr<SUP>III</SUP>(O<SUB>2</SUB>)(TMC)(Cl)]<SUP>+</SUP>, is an active oxidant in oxygen atom transfer (OAT) reactions, such as the oxidation of phosphine and sulfides. The electrophilic character of the Cr(III)–superoxo complex is demonstrated unambiguously in the sulfoxidation of <I>para</I>-substituted thioanisoles. A Cr(IV)–oxo complex, [Cr<SUP>IV</SUP>(O)(TMC)(Cl)]<SUP>+</SUP>, formed in the OAT reactions by the chromium(III)–superoxo complex, is characterized by X-ray crystallography and various spectroscopic methods. The present results support the proposed oxidant and mechanism in CDO, such as an iron(III)–superoxo species is an active oxidant that attacks the sulfur atom of the cysteine ligand by the terminal oxygen atom of the superoxo group, followed by the formation of a sulfoxide and an iron(IV)–oxo species via an O–O bond cleavage.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-27/ja304357z/production/images/medium/ja-2012-04357z_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja304357z'>ACS Electronic Supporting Info</A></P>

Geometric and electronic structure and reactivity of a mononuclear ‘side-on’ nickel(iii)–peroxo complex

Cho, Jaeheung,Sarangi, Ritimukta,Annaraj, Jamespandi,Kim, Sung Yeon,Kubo, Minoru,Ogura, Takashi,Solomon, Edward I.,Nam, Wonwoo Nature Publishing Group 2009 Nature chemistry Vol.1 No.7

Metal-dioxygen adducts, such as metal-superoxo and -peroxo species, are key intermediates often detected in the catalytic cycles of dioxygen activation by metalloenzymes and biomimetic compounds. The synthesis and spectroscopic characterization of an end-on nickel(II)-superoxo complex with a 14-membered macrocyclic ligand was reported previously. Here we report the isolation, spectroscopic characterization, and high-resolution crystal structure of a mononuclear side-on nickel(III)-peroxo complex with a 12-membered macrocyclic ligand, [Ni(12-TMC)(O<SUB>2</SUB>)]<SUP>+</SUP> (1) (12-TMC = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane). In contrast to the end-on nickel(II)-superoxo complex, the nickel(III)-peroxo complex is not reactive in electrophilic reactions, but is capable of conducting nucleophilic reactions. The nickel(III)-peroxo complex transfers the bound dioxygen to manganese(II) complexes, thus affording the corresponding nickel(II) and manganese(III)-peroxo complexes. Our results demonstrate the significance of supporting ligands in tuning the geometric and electronic structures and reactivities of metal–O<SUB>2</SUB> intermediates that have been shown to have biological as well as synthetic usefulness in biomimetic reactions.

Anesthetic efficacy of an inferior alveolar nerve block in soft tissue and correlation between soft tissue and pulpal anesthesia

Cho, Sin-Yeon,Choi, Wonwoo,Kim, Junyoung,Kim, Sung-Taek,Kim, Hee-Jin,Jung, Il-Young Springer-Verlag 2019 Clinical oral investigations Vol.23 No.3

A theoretical study into a <i>trans</i>-dioxo Mn^V porphyrin complex that does not follow the oxygen rebound mechanism in C–H bond activation reactions

Cho, Kyung-Bin,Nam, Wonwoo The Royal Society of Chemistry 2016 Chemical communications Vol.52 No.5

<P>Previous experimental results revealed that the C-H bond activation reaction by a synthetic trans-dioxo Mn-V porphyrin complex, [(TF(4)TMAP)(OMnO)-O-V](3+), does not occur via the well-known oxygen rebound mechanism, which has been well demonstrated in (FeO)-O-IV porphyrin pi-cation radical reactions. In the present study, theoretical calculations offer an explanation through the energetics involved in the C-H bond activation reaction, where a multi-spin state scenario cannot be excluded.</P>

Nonheme iron-oxo and -superoxo reactivities: O₂ binding and spin inversion probability matter

Cho, Kyung-Bin,Chen, Hui,Janardanan, Deepa,de Visser, Sam P.,Shaik, Sason,Nam, Wonwoo The Royal Society of Chemistry 2012 Chemical communications Vol.48 No.16

<P>DFT calculated barriers for C–H activation of 1,4-cyclohexadiene by nonheme iron(<SMALL>IV</SMALL>)-oxo and iron(<SMALL>III</SMALL>)-superoxo species show that the experimental trends can be explained if the spin inversion probability of the TMC iron(<SMALL>IV</SMALL>)-oxo is assumed to be poor. Also, the TMC iron(<SMALL>III</SMALL>)-superoxo reaction proceeds with an endothermic O<SUB>2</SUB>-binding energy followed by an intrinsically reactive quintet state.</P> <P>Graphic Abstract</P><P>DFT calculations on C–H activation by nonheme iron(<SMALL>IV</SMALL>)-oxo and iron(<SMALL>III</SMALL>)-superoxo species are done to compare their reactivities and spin states. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cc17610f'> </P>