Metal ion-coupled and decoupled electron transfer

Fukuzumi, Shunichi,Ohkubo, Kei Elsevier 2010 Coordination Chemistry Reviews Vol. No.

<P><B>Abstract</B></P><P>Effects of metal ions on thermal and photoinduced electron-transfer reactions from electron donors (D) to electron acceptors (A) are reviewed in terms of metal ion-coupled electron transfer (MCET) vs. metal ion-decoupled electron transfer (MDET). When electron transfer from D to A is coupled with binding of metal ions to A<SUP>−</SUP>, such an electron transfer is defined as MCET in which metal ions accelerate the rates of electron transfer. A number of examples of electron-transfer reactions from D to A, which are energetically impossible to occur, are made possible by strong binding of metal ions to A<SUP>−</SUP> in MCET. The structures of metal ion complexes with A<SUP>−</SUP> are also discussed in relation with the MCET reactivity. The MCET reactivity of metal ions is shown to be enhanced with an increase in the Lewis acidity of metal ions. In contrast to MCET, strong binding of metal ions to A<SUP>−</SUP> results in deceleration of back electron transfer from metal ion complexes of A<SUP>−</SUP> to D<SUP>+</SUP> in the radical ion pair, which is produced by photoinduced electron transfer from D to A in the presence of metal ions, as compared with back electron transfer without metal ions. The deceleration of back electron transfer in the presence of metal ions results from no binding of metal ions to A. This type of electron transfer is defined as metal ion-decoupled electron transfer (MDET). The lifetimes of CS state (D<SUP>+</SUP>–A<SUP>−</SUP>) produced by photoinduced electron transfer from D to A in the D–A linked systems are also elongated by adding metal ions to the D–A systems because of the stabilization of the CS states by strong binding of metal ions to A<SUP>−</SUP> and the resulting slow MDET processes.</P>

Contrasting Effects of Axial Ligands on Electron-Transfer Versus Proton-Coupled Electron-Transfer Reactions of Nonheme Oxoiron(IV) Complexes

Fukuzumi, Shunichi,Kotani, Hiroaki,Suenobu, Tomoyoshi,Hong, Seungwoo,Lee, Yong-Min,Nam, Wonwoo WILEY-VCH Verlag 2010 Chemistry Vol.16 No.1

<P>The effects of axial ligands on electron-transfer and proton-coupled electron-transfer reactions of mononuclear nonheme oxoiron(IV) complexes were investigated by using [Fe<SUP>IV</SUP>(O)(tmc)(X)]<SUP>n+</SUP> (1-X) with various axial ligands, in which tmc is 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane and X is CH<SUB>3</SUB>CN (1-NCCH<SUB>3</SUB>), CF<SUB>3</SUB>COO<SUP>−</SUP> (1-OOCCF<SUB>3</SUB>), or N<SUB>3</SUB><SUP>−</SUP> (1-N<SUB>3</SUB>), and ferrocene derivatives as electron donors. As the binding strength of the axial ligands increases, the one-electron reduction potentials of 1-X (E<SUB>red</SUB>, V vs. saturated calomel electrode (SCE)) are more negatively shifted by the binding of the more electron-donating axial ligands in the order of 1-NCCH<SUB>3</SUB> (0.39) > 1-OOCCF<SUB>3</SUB> (0.13) > 1-N<SUB>3</SUB> (−0.05 V). Rate constants of electron transfer from ferrocene derivatives to 1-X were analyzed in light of the Marcus theory of electron transfer to determine reorganization energies (λ) of electron transfer. The λ values decrease in the order of 1-NCCH<SUB>3</SUB> (2.37) > 1-OOCCF<SUB>3</SUB> (2.12) > 1-N<SUB>3</SUB> (1.97 eV). Thus, the electron-transfer reduction becomes less favorable thermodynamically but more favorable kinetically with increasing donor ability of the axial ligands. The net effect of the axial ligands is the deceleration of the electron-transfer rate in the order of 1-NCCH<SUB>3</SUB> > 1-OOCCF<SUB>3</SUB> > 1-N<SUB>3</SUB>. In sharp contrast to this, the rates of the proton-coupled electron-transfer reactions of 1-X are markedly accelerated in the presence of an acid in the opposite order: 1-NCCH<SUB>3</SUB> < 1-OOCCF<SUB>3</SUB> < 1-N<SUB>3</SUB>. Such contrasting effects of the axial ligands on the electron-transfer and proton-coupled electron-transfer reactions of nonheme oxoiron(IV) complexes are discussed in light of the counterintuitive reactivity patterns observed in the oxo transfer and hydrogen-atom abstraction reactions by nonheme oxoiron(IV) complexes (Sastri et al. Proc. Natl. Acad. Sci. U.S.A. 2007, 104, 19 181–19 186).</P> <B>Graphic Abstract</B> <P>Counterintuitive reactivities: The rates of electron transfer (ET) and proton-coupled electron-transfer (PCET) in the reactions of with ferrocene derivatives are markedly affected by the electron-donating ability of the axial ligands (X) in opposite directions (see figure); the electron-donating axial ligand decelerates the ET rate in the reactions, but enhances the PCET reactivity of 1-X in the presence of acid. <img src='wiley_img/09476539-2010-16-1-CHEM200901163-content.gif' alt='wiley_img/09476539-2010-16-1-CHEM200901163-content'> </P>

전자자금이체에 관한 연구

이창운 한국금융법학회 2015 金融法硏究 Vol.12 No.1

Electronic Financial Transactions Act of Korea was enacted to solve the many issues associated with electronic financial transaction in 2007. And the amendment was made over 10 times since then. However, the problems associated with it also appears continuously in accordance with the continuous development of electronic financial transactions. Accordingly, in this paper, we studied the regulations and its problems and improvement of an electronic funds transfer among electronic financial transactions. This paper is composed of all seven chapters, the topics covered in each chapter are as follows : Chapter Ⅰ Introduction : South Korea's payment system, enactment and amendment of Electronic Financial Transactions Act, and legal issues associated with electronic funds transfer are described. Chapter Ⅱ The significance of electronic funds transfer : Regulations on electronic funds transfer and the significance of electronic funds transfer in South Korea, the significance of electronic funds transfer in the foreign law were summarized. Chapter Ⅲ Legal relationship between the parties to the electronic funds transfer : Legal relationship between the parties to transfer payment, and legal relationship between the parties to collection transfer were studied. Chapter Ⅳ Legal issues associated with electronic funds transfer : Effective time of the electronic funds transfer, transfer error, loss or theft of the access material, assignment of the access material, transfer-related accidents, failure to transfer instructions, error transfer to the recipient were studied. Also my personal opinion about it was said. Chapter Ⅴ Legal issues of telecommunications financial fraud : The significance of telecommunication financial fraud and relief of telecommunications financial fraud victims were described. Chapter Ⅵ : Problems and Solutions : We discussed the issues that require amendment of Electronic Financial Transactions Act and General Terms and Conditions for electronic financial transactions, and then proposed improvement measures. Chapter Ⅶ Conclusion : The main information of this papers was summarized.

Electron-transfer properties of high-valent metal-oxo complexes

Elsevier Publishing Company 2013 Coordination chemistry reviews Vol.257 No.9

Electron-transfer properties of heme and non-heme high-valent metal-oxo complexes are overviewed in relation to their reactivity toward oxidation of substrates. The rate constants of electron transfer from a series of electron donors to various heme and non-heme high-valent metal-oxo complexes such as compound I and compound II of horseradish peroxidase (HRP), (TMP)Mn<SUP>IV</SUP>(O) ((TMP=tetramesityl-porphyrinate dianion), (TBP<SUB>8</SUB>Cz)Mn<SUP>V</SUP>(O) (TBP<SUB>8</SUB>Cz=octa-tert-butylphenylcorrolazinate trianion) and [(L)Fe<SUP>IV</SUP>(O)]<SUP>2+</SUP>, where L=TMC, 1,4,8,11-tetra-methyl-1,4,8,11-tetraazacyclotetradecane; Bn-TPEN, N-benzyl-N,N',N'-tris(2-pyridylmethyl)ethane-1,2-diamine; N4Py, N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine; bisp, 3,7-diazabicyclo[3.3.1]nonane) were evaluated in light of the Marcus theory of electron transfer in order to determine the reorganization energy (λ) for electron transfer. The λ value increases in the order: 1.3eV (compound I of HRP), 1.53eV [(TBP<SUB>8</SUB>Cz)Mn<SUP>V</SUP>(O)], 1.6eV (compound II of HRP), 1.7eV [(TMP)Mn<SUP>IV</SUP>(O)], 2.05eV [(bisp)Fe<SUP>IV</SUP>(O)]<SUP>2+</SUP>, 2.37eV [(TMC)Fe<SUP>IV</SUP>(O)]<SUP>2+</SUP>), 2.55eV ([(Bn-TPEN)Fe<SUP>IV</SUP>(O)]<SUP>2+</SUP>), 2.74eV ([(N4Py)Fe<SUP>IV</SUP>(O)]<SUP>2+</SUP>). The λ value of compound I of HRP is the smallest among those of high-valent metal-oxo complexes, because the site of the reduction is on the porphyrin ligand, whereas the site of the reduction is on the metal for the other high-valent metal-oxo complexes. The λ values of high-valent metal-oxo porphyrins are generally smaller than those of non-heme iron(IV)-oxo complexes. The effects of Lewis acidic metal ions and Bronsted acids on the one-electron reduction of high-valent metal-oxo complexes are also overviewed in relation to their enhancement of the oxidizing ability towards reductants.

주제별 논단 : 연구논문 ; 전자자금이체에 관한 연구

이창운 ( Chang Woon Lee ) 한국금융법학회 2015 金融法硏究 Vol.12 No.1

Electronic Financial Transactions Act of Korea was enacted to solve the many issues associated with electronic financial transaction in 2007. And the amendment was made over 10 times since then. However, the problems associated with it also appears continuously in accordance with the continuous development of electronic financial transactions. Accordingly, in this paper, we studied the regulations and its problems and improvement of an electronic funds transfer among electronic financial transactions. This paper is composed of all seven chapters, the topics covered in each chapter are as follows : Chapter Ⅰ Introduction : South Korea``s payment system, enactment and amendment of Electronic Financial Transactions Act, and legal issues associated with electronic funds transfer are described. Chapter Ⅱ The significance of electronic funds transfer : Regulations on electronic funds transfer and the significance of electronic funds transfer in South Korea, the significance of electronic funds transfer in the foreign law were summarized. Chapter Ⅲ Legal relationship between the parties to the electronic funds transfer : Legal relationship between the parties to transfer payment, and legal relationship between the parties to collection transfer were studied. Chapter Ⅳ Legal issues associated with electronic funds transfer : Effective time of the electronic funds transfer, transfer error, loss or theft of the access material, assignment of the access material, transfer-related accidents, failure to transfer instructions, error transfer to the recipient were studied. Also my personal opinion about it was said. Chapter Ⅴ Legal issues of telecommunications financial fraud : The significance of telecommunication financial fraud and relief of telecommunications financial fraud victims were described. Chapter Ⅵ Problems and Solutions : We discussed the issues that require amendment of Electronic Financial Transactions Act and General Terms and Conditions for electronic financial transactions, and then proposed improvement measures. Chapter Ⅶ Conclusion : The main information of this papers was summarized.

Construction of Uniform Monolayer- and Orientation-Tunable Enzyme Electrode by a Synthetic Glucose Dehydrogenase without Electron-Transfer Subunit via Optimized Site-Specific Gold-Binding Peptide Capable of Direct Electron Transfer

Lee, Yoo Seok,Baek, Seungwoo,Lee, Hyeryeong,Reginald, Stacy Simai,Kim, Yeongeun,Kang, Hyunsoo,Choi, In-Geol,Chang, In Seop American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.34

<P>Direct electron transfer (DET) between enzymes and electrodes is a key issue for practical use of bioelectrocatalytic devices as a bioenergy process, such as enzymatic electrosynthesis, biosensors, and enzyme biofuel cells. To date, based on the DET of bioelectrocatalysis, less than 1% of the calculated theoretical current was transferred to final electron acceptor due to energy loss at enzyme-electrode interface. This study describes the design and construction of a synthetic glucose dehydrogenase (GDH; α and γ subunits) combined with a gold-binding peptide at its amino or carboxy terminus for direct contact between enzyme and electrode. The fused gold-binding peptide facilitated stable immobilization of GDH and constructed uniform monolayer of GDH onto a Au electrode. Depending on the fused site of binding peptide to the enzyme complex, nine combinations of recombinant GDH proteins on the electrode show significantly different direct electron-transfer efficiency across the enzyme-electrode interface. The fusion of site-specific binding peptide to the catalytic subunit (α subunit, carboxy terminus) of the enzyme complex enabled apparent direct electron transfer (DET) across the enzyme-electrode interface even in the absence of the electron-transfer subunit (i.e., β subunit having cytochrome domain). The catalytic glucose oxidation current at an onset potential of ca. (−)0.46 V vs Ag/AgCl was associated with the appearance of an flavin adenine dinucleotide (FAD)/FADH<SUB>2</SUB> redox wave and a stabilized bioelectrocatalytic current of more than 100 μA, determined from chronoamperometric analysis. Electron recovery was 7.64%, and the catalytic current generation was 249 μA per GDH enzyme loading unit (U), several orders of magnitude higher than the values reported previously. These observations corroborated that the last electron donor facing to electrode was controlled to be in close proximity without electron-transfer intermediates and the native affinity for glucose was preserved. The design and construction of the site-specific “sticky-ended” proteins without loss of catalytic activity could be applied to other redox enzymes having a buried active site.</P> [FIG OMISSION]</BR>

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.

전자지급거래의 법적 규율에 관한 비교법적 검토

제철웅(Cheolung Je) 한국비교사법학회 2011 比較私法 Vol.18 No.2

For the last three decades the technological development has made electronic fund transfers so widely employed in the payment service industry as to replace paper based payments with paper‐less ones, which has been materialized by the introduction and wide use of payment cards, giro transfers including standing orders and direct debits, and electronic money and which trend has eventually been extended to international payment transactions. Whereas they have certainly brought about enormous benefits to the society as well as individuals, electronic fund transfers have occasionally been exposed to unexpected risks. Not to mention liquidity, credit and systemic risk of the payment systems, which in turn affects individuals involved respectively, the parties to the payment transactions used to be exposed to the risk of uncertainty surrounding legal relations between them, due to the fact that even though many persons concerned were involed even in a simple electronic fund transfer, for instance 3 or 4 parties in a card payment transaction, legal provisions governing such relations, in many countries, remained conventional civil law, mostly formulated or enacted hundreds years before electronic fund transfers appeared on the payment service market, meaning that such conventional law are hardly suitable enough to provide for appropriate solutions to disputes arising from new payment transactions. In this respect, the USA has treaded a new land for the first time as a pioneer in that in 1978, the Electronic Fund Transfer Act of 1978 as well as the Truth in Lending Act of 1968 , both contained in the Consumer Credit Protection Act, was enacted for the consumers protection purposes in the electronic fund ftransfers market, in addition to which UCC Article 4A of 1989 was drafted whereby it was meant to substitute conventional common law provisions with regard to credit transfers. The EU soon followed the USA model in this regard by the enactment of Consumer Credit Directive 87/102/EEC, Distance Contracts Directive 97/7/EC, Credit Transfer Directive 97/5/EC and Cross‐Border Euro Payment Regulation 2560/2001 so as to harmonise national laws of the Member States, even thogh partially. With the entry into force of the Payment Service Directive 2007/64/EC and Regulation 924/2009, the EU has eventually harmonized national laws of the Member States on the legal relations between payment service providers and payment service users in so many respects that the scope of the application of conventional civil law provisions to such relations comes to be as much narrowed as the EU can do it without harmonizing civil laws directly and indirectly related to contracts. Korea is to be classified as a special statute jurisdiction in terms of by which law legal relations between payment services providers and payment service users are governed, for the Electronic Financial Transaction Act was enacted in 2007 so as to regulate all kinds of electronic fund transfers, which is at the time of writing flanked by other special statutes for the consumer protection in the field of credit transaction and electronic commercial transaction and so on. Such special statutes, especially the Electronic Financial Transaction Act, are basically in line with the EFTA and UCC Article 4A in the USA and the Payment Service Directive and some Directives for consumer protection purposes. After it analyses main features of the said USA and EU laws for the purpose of comparing them with Korean special statutes, this paper suggests that there be additional legislative initiatives to strengthen consumer protection in electronic fund transfer transaction and to further narrow the application of conventional civil law provisions to such transactions, which is presumably essential for the payment service transactions to be made to appropriately function without damaging participants thereto inappropriately.

Heterogeneous Electron Transfer at Polyoxometalate-modified Electrode Surfaces

Choi, Su-Hee,Seo, Bo-Ra,Kim, Jong-Won Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.1

The heterogeneous electron transfer at $SiMo_{12}O_{40}^{4-}$ monolayers on GC, HOPG, and Au electrode surfaces are investigated using cyclic voltammetric and electrochemical impedance spectroscopic (EIS) methods. The electron transfer of negatively charged $Fe(CN)_6^{3-}$ species is retarded at $SiMo_{12}O_{40}^{4-}$-modified electrode surfaces, while that of positively charged $Ru(NH_3)_6^{3+}$species is accelerated at the modified surfaces. This is due to the electrostatic interactions between $SiMo_{12}O_{40}^{4-}$ layers on surfaces and charged redox species. The electron transfer kinetics of a neutral redox species, 1,1‘-ferrocenedimethanol (FDM), is not affected by the modification of electrode surfaces with $SiMo_{12}O_{40}^{4-}$, indicating the $SiMo_{12}O_{40}^{4-}$ monolayers do not impart barriers to electron transfer of neutral redox species. This is different from the case of thiolate SAMs which always add barriers to electron transfer. The effect of $SiMo_{12}O_{40}^{4-}$ layers on the electron transfer of charged redox species is dependent on the kind of electrodes, where HOPG surfaces exhibit marked effects. Possible mechanisms responsible for different electron transfer behaviors at $SiMo_{12}O_{40}^{4-}$ layers are proposed.

Oxidation Leading to Reduction: Redox-Induced Electron Transfer (RIET)

Miller, Joel S.,Min, Kil Sik WILEY-VCH Verlag 2009 Angewandte Chemie Vol.48 No.2

<P>Complex electron transfer reactions have been characterized whereby in addition to electron transfer, subsequent electrochemical, chemical and even in some cases biological consequences occur. These include a secondary electron transfer that leads to a major rearrangement of the electronic structure, such that an initial oxidation leads to a reduction (or an initial reduction leads to an oxidation) for these valence ambiguous compounds. Mixed valency and valence-tautomeric behaviors can additionally result from these complex electron-transfer-induced reactions.</P> <B>Graphic Abstract</B> <P>Redox paradox? The initial one-electron oxidation of a metal ion induces a multi-electron rearrangement, leading to oxidation of the second metal ion and reduction of the tetraoxolate dianionic ligand bridging the two metals (see scheme). These electron-transfer events were observed with numerous spectroscopic, electrochemical, and crystallographic methods (TpyA=tris(2-pyridylmethylamine). <img src='wiley_img/14337851-2009-48-2-ANIE200705138-content.gif' alt='wiley_img/14337851-2009-48-2-ANIE200705138-content'> </P>