Kinetics and thermodynamics of formation and electron-transfer reactions of Cu-O₂ and Cu₂-O₂ complexes

Fukuzumi, S.,Karlin, K.D. Elsevier Publishing Company 2013 Coordination chemistry reviews Vol.257 No.1

The kinetics and thermodynamics of formation of Cu(II)-superoxo (Cu-O<SUB>2</SUB>) complexes by the reaction of Cu(I) complexes with dioxygen (O<SUB>2</SUB>) and the reduction of Cu(II)-superoxo complexes to dinuclear Cu-peroxo complexes are discussed. In the former case, electron transfer from a Cu(I) complex to O<SUB>2</SUB> occurs concomitantly with binding of O<SUB>2</SUB><SUP>?-</SUP>to the corresponding Cu(II) species. This is defined as an inner-sphere Cu(II) ion-coupled electron transfer process. Electron transfer from another Cu(I) complex to preformed Cu(II)-superoxo complexes also occurs concomitantly with binding of the Cu(II)-peroxo species with the Cu(II) species to produce the dinuclear Cu-peroxo (Cu<SUB>2</SUB>-O<SUB>2</SUB>) complexes. The kinetics and thermodynamics of outer-sphere electron-transfer reduction of Cu<SUB>2</SUB>-O<SUB>2</SUB> complexes are also been discussed in light of the Marcus theory of outer-sphere electron transfer.

Enhanced Catalytic Four-Electron Dioxygen (O₂) and Two-Electron Hydrogen Peroxide (H₂O₂) Reduction with a Copper(II) Complex Possessing a Pendant Ligand Pivalamido Group

Kakuda, Saya,Peterson, Ryan L.,Ohkubo, Kei,Karlin, Kenneth D.,Fukuzumi, Shunichi American Chemical Society 2013 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.135 No.17

<P>A copper complex, [(PV-tmpa)Cu<SUP>II</SUP>](ClO<SUB>4</SUB>)<SUB>2</SUB> (<B>1</B>) [PV-tmpa = bis(pyrid-2-ylmethyl){[6-(pivalamido)pyrid-2-yl]methyl}amine], acts as a more efficient catalyst for the four-electron reduction of O<SUB>2</SUB> by decamethylferrocene (Fc*) in the presence of trifluoroacetic acid (CF<SUB>3</SUB>COOH) in acetone as compared with the corresponding copper complex without a pivalamido group, [(tmpa)Cu<SUP>II</SUP>](ClO<SUB>4</SUB>)<SUB>2</SUB> (<B>2</B>) (tmpa = tris(2-pyridylmethyl)amine). The rate constant (<I>k</I><SUB>obs</SUB>) of formation of decamethylferrocenium ion (Fc*<SUP>+</SUP>) in the catalytic four-electron reduction of O<SUB>2</SUB> by Fc* in the presence of a large excess CF<SUB>3</SUB>COOH and O<SUB>2</SUB> obeyed first-order kinetics. The <I>k</I><SUB>obs</SUB> value was proportional to the concentration of catalyst <B>1</B> or <B>2</B>, whereas the <I>k</I><SUB>obs</SUB> value remained constant irrespective of the concentration of CF<SUB>3</SUB>COOH or O<SUB>2</SUB>. This indicates that electron transfer from Fc* to <B>1</B> or <B>2</B> is the rate-determining step in the catalytic cycle of the four-electron reduction of O<SUB>2</SUB> by Fc* in the presence of CF<SUB>3</SUB>COOH. The second-order catalytic rate constant (<I>k</I><SUB>cat</SUB>) for <B>1</B> is 4 times larger than the corresponding value determined for <B>2</B>. With the pivalamido group in <B>1</B> compared to <B>2</B>, the Cu<SUP>II</SUP>/Cu<SUP>I</SUP> potentials are –0.23 and –0.05 V vs SCE, respectively. However, during catalytic turnover, the CF<SUB>3</SUB>COO<SUP>–</SUP> anion present readily binds to <B>2</B> shifting the resulting complex’s redox potential to –0.35 V. The pivalamido group in <B>1</B> is found to inhibit anion binding. The overall effect is to make <B>1</B> easier to reduce (relative to <B>2</B>) during catalysis, accounting for the relative <I>k</I><SUB>cat</SUB> values observed. <B>1</B> is also an excellent catalyst for the two-electron two-proton reduction of H<SUB>2</SUB>O<SUB>2</SUB> to water and is also more efficient than is <B>2</B>. For both complexes, reaction rates are greater than for the overall four-electron O<SUB>2</SUB>-reduction to water, an important asset in the design of catalysts for the latter.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2013/jacsat.2013.135.issue-17/ja3125977/production/images/medium/ja-2012-125977_0017.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja3125977'>ACS Electronic Supporting Info</A></P>

An isoelectronic NO dioxygenase reaction using a nonheme iron(<small>III</small>)-peroxo complex and nitrosonium ion

Yokoyama, Atsutoshi,Han, Jung Eun,Karlin, Kenneth D.,Nam, Wonwoo The Royal Society of Chemistry 2014 Chemical communications Vol.50 No.14

<P>Reaction of a nonheme iron(<SMALL>III</SMALL>)-peroxo complex, [Fe<SUP>III</SUP>(14-TMC)(O<SUB>2</SUB>)]<SUP>+</SUP>, with NO<SUP>+</SUP>, a transformation which is essentially isoelectronic with that for nitric oxide dioxygenases [Fe(<SMALL>III</SMALL>)(O<SUB>2</SUB>&z.rad;<SUP>−</SUP>) + NO], affords an iron(<SMALL>IV</SMALL>)-oxo complex, [Fe<SUP>IV</SUP>(14-TMC)(O)]<SUP>2+</SUP>, and nitrogen dioxide (NO<SUB>2</SUB>), followed by conversion to an iron(<SMALL>III</SMALL>)-nitrato complex, [Fe<SUP>III</SUP>(14-TMC)(NO<SUB>3</SUB>)(F)]<SUP>+</SUP>.</P> <P>Graphic Abstract</P><P>Reaction of a nonheme iron(<SMALL>III</SMALL>)-peroxo complex, [Fe<SUP>III</SUP>(14-TMC)(O<SUB>2</SUB>)]<SUP>+</SUP>, with NO<SUP>+</SUP> affords an iron(<SMALL>IV</SMALL>)-oxo complex, [Fe<SUP>IV</SUP>(14-TMC)(O)]<SUP>2+</SUP>, and nitrogen dioxide (NO<SUB>2</SUB>), followed by conversion to the nitrato complex, [Fe<SUP>III</SUP>(14-TMC)(NO<SUB>3</SUB>)(F)]<SUP>+</SUP>. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cc48782b'> </P>

Improvement of durability of an organic photocatalyst in <i>p</i>-xylene oxygenation by addition of a Cu(<small>II</small>) complex

Yamada, Yusuke,Maeda, Kazuki,Ohkubo, Kei,Karlin, Kenneth D.,Fukuzumi, Shunichi The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.27

<P>The catalytic durability of an organic photocatalyst, 9-mesityl-10-methyl acridinium ion (Acr<SUP>+</SUP>–Mes), has been dramatically improved by the addition of [{tris(2-pyridylmethyl)amine}Cu<SUP>II</SUP>](ClO<SUB>4</SUB>)<SUB>2</SUB> ([(tmpa)Cu<SUP>II</SUP>]<SUP>2+</SUP>) in the photocatalytic oxygenation of <I>p</I>-xylene by molecular oxygen in acetonitrile. Such an improvement is not observed by the addition of Cu(ClO<SUB>4</SUB>)<SUB>2</SUB> in the absence of organic ligands. The addition of [(tmpa)Cu]<SUP>2+</SUP> in the reaction solution resulted in more than an 11 times higher turnover number (TON) compared with the TON obtained without [(tmpa)Cu<SUP>II</SUP>]<SUP>2+</SUP>. In the photocatalytic oxygenation, a stoichiometric amount of H<SUB>2</SUB>O<SUB>2</SUB> formation was observed in the absence of [(tmpa)Cu<SUP>II</SUP>]<SUP>2+</SUP>, however, much less H<SUB>2</SUB>O<SUB>2</SUB> formation was observed in the presence of [(tmpa)Cu<SUP>II</SUP>]<SUP>2+</SUP>. The photocatalytic mechanism was investigated by laser flash photolysis measurements in order to detect intermediates. The reaction of O<SUB>2</SUB>&z.rad;<SUP>−</SUP> with [(tmpa)Cu<SUP>II</SUP>]<SUP>2+</SUP> monitored by UV-vis spectroscopy in propionitrile at 203 K suggested formation of [{(tmpa)Cu<SUP>II</SUP>}<SUB>2</SUB>O<SUB>2</SUB>]<SUP>2+</SUP>, a transformation which is crucial for the overall 4-electron reduction of molecular O<SUB>2</SUB> to water, and a key in the observed improvement in the catalytic durability of Acr<SUP>+</SUP>–Mes.</P> <P>Graphic Abstract</P><P>The activity of [(tmpa)Cu<SUP>II</SUP>]<SUP>2+</SUP> complex toward reactive oxygen species elongates the catalytic durability of an organic photocatalyst. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp41207a'> </P>

Copper–Dioxygen Reactivity Using Dinucleating Ligands with Activated Methylene or Ketone Function

Lee, Dong-Heon,Murthy, Narasimha N.,Karlin, Kenneth D. Chemical Society of Japan 2007 Bulletin of the Chemical Society of Japan Vol.80 No.4

<P>Copper(I)–dioxygen reactivity studies utilizing new binucleating ligands are described. When catalytic quantities of either Cu<SUP>I</SUP> or Cu<SUP>II</SUP> salts were introduced to <B>LH<SUB>2</SUB></B>, which is a dinucleating ligand with two tridentate donors connected via a methylene group at a bis(2-pyridyl)methane junction, dioxygen addition caused complete oxygenation to give bis(2-pyridyl)ketone product <B>L=O</B>. Isolated dicopper(I) complex [Cu<SUP>I</SUP><SUB>2</SUB>(<B>LH<SUB>2</SUB></B>)]<SUP>2+</SUP> (<B>1</B>) also reacted with excess O<SUB>2</SUB> to give <B>L=O</B>. Additional observations were consistent with a mechanism that does not involve “oxygen-activation” in this process. Ketone hydration and <I>gem</I>-diol(ate) copper(II)-coordination occurred by addition of copper(II)–perchlorate to <B>L=O</B>, giving [Cu<SUP>II</SUP><SUB>2</SUB>{<B>L(OH)(O<SUP>−</SUP>)</B>}Cu<SUB>2</SUB><SUP>II</SUP>(<SUP>−</SUP>OClO<SUB>3</SUB>)]<SUP>2+</SUP> (<B>4</B>), with a bridging alkoxide moiety (X-ray). Oxygenation of [Cu<SUP>I</SUP><SUB>2</SUB>(<B>L=O</B>)(CH<SUB>3</SUB>CN)<SUB>2</SUB>]<SUP>2+</SUP> (<B>2</B>) (<B>2</B>/O<SUB>2</SUB> = 0.5, i.e., Cu/O<SUB>2</SUB> = 4:1 manometry), gave [Cu<SUP>II</SUP><SUB>2</SUB>{<B>L(O<SUP>−</SUP>)<SUB>2</SUB></B>}(<SUP>−</SUP>OClO<SUB>3</SUB>)]<SUP>+</SUP> (<B>5</B>), where both oxygen atoms of the doubly deprotonated <I>gem</I>-diolate bind separate copper(II) ions; mass spectrometric data showed that one of the two oxygen atoms of the <I>gem</I>-diolate <B>L(O<SUP>−</SUP>)<SUB>2</SUB></B> came from O<SUB>2</SUB>. An oxo–dicopper(II) species is suggested as an important intermediate, which is supported by the observation that reaction of <B>2</B> with NO or iodosylbenzene also produced <B>5</B> in high yields. Complexes <B>4</B> and <B>5</B> are acid–base conjugate pairs and can be readily interconverted using Et<SUB>3</SUB>N or HClO<SUB>4(aq)</SUB> reagents.</P>

FGFR2 variants and breast cancer risk: fine-scale mapping using African American studies and analysis of chromatin conformation.

Udler, Miriam S,Meyer, Kerstin B,Pooley, Karen A,Karlins, Eric,Struewing, Jeffery P,Zhang, Jinghui,Doody, David R,MacArthur, Stewart,Tyrer, Jonathan,Pharoah, Paul D,Luben, Robert,Bernstein, Leslie,Kol IRL Press ; Oxford University Press 2009 Human Molecular Genetics Vol.18 No.9

<P>Genome-wide association studies have identified FGFR2 as a breast cancer (BC) susceptibility gene in populations of European and Asian descent, but a causative variant has not yet been conclusively identified. We hypothesized that the weaker linkage disequilibrium across this associated region in populations of African ancestry might help refine the set of candidate-causal single nucleotide polymorphisms (SNPs) previously identified by our group. Eight candidate-causal SNPs were evaluated in 1253 African American invasive BC cases and 1245 controls. A significant association with BC risk was found with SNP rs2981578 (unadjusted per-allele odds ratio = 1.20, 95% confidence interval 1.03-1.41, P(trend) = 0.02), with the odds ratio estimate similar to that reported in European and Asian subjects. To extend the fine-mapping, genotype data from the African American studies were analyzed jointly with data from European (n = 7196 cases, 7275 controls) and Asian (n = 3901 cases, 3205 controls) studies. In the combined analysis, SNP rs2981578 was the most strongly associated. Five other SNPs were too strongly correlated to be excluded at a likelihood ratio of < 1/100 relative to rs2981578. Analysis of DNase I hypersensitive sites indicated that only two of these map to highly accessible chromatin, one of which, SNP rs2981578, has previously been implicated in up-regulating FGFR2 expression. Our results demonstrate that the association of SNPs in FGFR2 with BC risk extends to women of African American ethnicity, and illustrate the utility of combining association analysis in datasets of diverse ethnic groups with functional experiments to identify disease susceptibility variants.</P>

Homogeneous catalytic O₂ reduction to water by a cytochrome c oxidase model with trapping of intermediates and mechanistic insights

Halime, Z.,Kotani, H.,Li, Y.,Fukuzumi, S.,Karlin, K.D. National Academy of Sciences 2011 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.108 No.34

Temperature-Independent Catalytic Two-Electron Reduction of Dioxygen by Ferrocenes with a Copper(II) Tris[2-(2-pyridyl)ethyl]amine Catalyst in the Presence of Perchloric Acid

Das, Dipanwita,Lee, Yong-Min,Ohkubo, Kei,Nam, Wonwoo,Karlin, Kenneth D.,Fukuzumi, Shunichi American Chemical Society 2013 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.135 No.7

<P>Selective two-electron plus two-proton (2e<SUP>–</SUP>/2H<SUP>+</SUP>) reduction of O<SUB>2</SUB> to hydrogen peroxide by ferrocene (Fc) or 1,1′-dimethylferrocene (Me<SUB>2</SUB>Fc) in the presence of perchloric acid is catalyzed efficiently by a mononuclear copper(II) complex, [Cu<SUP>II</SUP>(tepa)]<SUP>2+</SUP> (<B>1</B>; tepa = tris[2-(2-pyridyl)ethyl]amine) in acetone. The <I>E</I><SUB>1/2</SUB> value for [Cu<SUP>II</SUP>(tepa)]<SUP>2+</SUP> as measured by cyclic voltammetry is 0.07 V vs Fc/Fc<SUP>+</SUP> in acetone, being significantly positive, which makes it possible to use relatively weak one-electron reductants such as Fc and Me<SUB>2</SUB>Fc for the overall two-electron reduction of O<SUB>2</SUB>. Fast electron transfer from Fc or Me<SUB>2</SUB>Fc to <B>1</B> affords the corresponding Cu<SUP>I</SUP> complex [Cu<SUP>I</SUP>(tepa)]<SUP>+</SUP> (<B>2</B>), which reacts at low temperature (193 K) with O<SUB>2</SUB>, however only in the presence of HClO<SUB>4</SUB>, to afford the hydroperoxo complex [Cu<SUP>II</SUP>(tepa)(OOH)]<SUP>+</SUP> (<B>3</B>). A detailed kinetic study on the homogeneous catalytic system reveals the rate-determining step to be the O<SUB>2</SUB>-binding process in the presence of HClO<SUB>4</SUB> at lower temperature as well as at room temperature. The O<SUB>2</SUB>-binding kinetics in the presence of HClO<SUB>4</SUB> were studied, demonstrating that the rate of formation of the hydroperoxo complex <B>3</B> as well as the overall catalytic reaction remained virtually the same with changing temperature. The apparent lack of activation energy for the catalytic two-electron reduction of O<SUB>2</SUB> is shown to result from the existence of a pre-equilibrium between <B>2</B> and O<SUB>2</SUB> prior to the formation of the hydroperoxo complex <B>3</B>. No further reduction of [Cu<SUP>II</SUP>(tepa)(OOH)]<SUP>+</SUP> (<B>3</B>) by Fc or Me<SUB>2</SUB>Fc occurred, and instead <B>3</B> is protonated by HClO<SUB>4</SUB> to yield H<SUB>2</SUB>O<SUB>2</SUB> accompanied by regeneration of <B>1</B>, thus completing the catalytic cycle for the two-electron reduction of O<SUB>2</SUB> by Fc or Me<SUB>2</SUB>Fc.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2013/jacsat.2013.135.issue-7/ja312523u/production/images/medium/ja-2012-12523u_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja312523u'>ACS Electronic Supporting Info</A></P>

Mononuclear Copper Complex-Catalyzed Four-Electron Reduction of Oxygen

Fukuzumi, Shunichi,Kotani, Hiroaki,Lucas, Heather R.,Doi, Kaoru,Suenobu, Tomoyoshi,Peterson, Ryan L.,Karlin, Kenneth D. American Chemical Society 2010 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.132 No.20

<P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2010/jacsat.2010.132.issue-20/ja100538x/production/images/medium/ja-2010-00538x_0002.gif'> <P>A mononuclear Cu<SUP>II</SUP> complex acts as an efficient catalyst for four-electron reduction of O<SUB>2</SUB> to H<SUB>2</SUB>O. Its reduction by a ferrocene derivative (Fc*) and reaction with O<SUB>2</SUB> leads to the formation of a peroxodicopper(II) complex; this is subsequently reduced by Fc* in the presence of protons to regenerate the Cu<SUP>II</SUP> complex.</P></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja100538x'>ACS Electronic Supporting Info</A></P>

Chromium(IV)–Peroxo Complex Formation and Its Nitric Oxide Dioxygenase Reactivity

Yokoyama, Atsutoshi,Han, Jung Eun,Cho, Jaeheung,Kubo, Minoru,Ogura, Takashi,Siegler, Maxime A.,Karlin, Kenneth D.,Nam, Wonwoo American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.37

<P>The O<SUB>2</SUB> and NO reactivity of a Cr(II) complex bearing a 12-membered tetraazamacrocyclic <I>N</I>-tetramethylated cyclam (TMC) ligand, [Cr<SUP>II</SUP>(12-TMC)(Cl)]<SUP>+</SUP> (<B>1</B>), and the NO reactivity of its peroxo derivative, [Cr<SUP>IV</SUP>(12-TMC)(O<SUB>2</SUB>)(Cl)]<SUP>+</SUP> (<B>2</B>), are described. By contrast to the previously reported Cr(III)–superoxo complex, [Cr<SUP>III</SUP>(14-TMC)(O<SUB>2</SUB>)(Cl)]<SUP>+</SUP>, the Cr(IV)–peroxo complex <B>2</B> is formed in the reaction of <B>1</B> and O<SUB>2</SUB>. Full spectroscopic and X-ray analysis revealed that <B>2</B> possesses side-on η<SUP>2</SUP>-peroxo ligation. The quantitative reaction of <B>2</B> with NO affords a reduction in Cr oxidation state, producing a Cr(III)–nitrato complex, [Cr<SUP>III</SUP>(12-TMC)(NO<SUB>3</SUB>)(Cl)]<SUP>+</SUP> (<B>3</B>). The latter is suggested to form via a Cr(III)–peroxynitrite intermediate. [Cr<SUP>II</SUP>(12-TMC)(NO)(Cl)]<SUP>+</SUP> (<B>4</B>), a Cr(II)–nitrosyl complex derived from <B>1</B> and NO, could also be synthesized; however, it does not react with O<SUB>2</SUB>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-37/ja307384e/production/images/medium/ja-2012-07384e_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja307384e'>ACS Electronic Supporting Info</A></P>