排序方式: 共有15条查询结果,搜索用时 15 毫秒
1.
Holanda Alda K.M. Pontes Daniel L. Diógenes Izaura C.N. Moreira Ícaro S. Lopes Luiz G.F. 《Transition Metal Chemistry》2004,29(4):430-436
The synthesis, characterization and reactivity of trans-[Ru(NH3)4(L)NO](PF6)3(L = benzoimidazole or 1-methylimidazole in trans position to NO) are presented. 1H-n.m.r. spectroscopy data indicate that the benzoimidazole and 1-methylimidazole ligands are coordinated to RuII through carbon and nitrogen, respectively. The nitrosyl stretching frequencies [(NO) > 1900 cm–1] suggest that the coordinated nitrosyl has substantial NO+ character. The complexes undergo a single-electron reduction (E
0–0.245 versus NHE), which involves the coordinated nitrosyl. Dissociation of NO in the reduced species is facilitated by the 1-methylimidazole ligand, which is not observed for the benzoimidazole species. The complex with 1-methylimidazole does not suffer hydroxide attack on the NO+, at least at pH values lower than 11. 相似文献
2.
Hydroxyl Radical Generation and DNA Nuclease Activity: A Mechanistic Study Based on a Surface‐Immobilized Copper Thioether Clip‐Phen Derivative 下载免费PDF全文
Adolfo I. B. Romo Dieric S. Abreu Dr. Tércio de F. Paulo Dr. Marta S. P. Carepo Prof. Eduardo H. S. Sousa Prof. Luis Lemus Prof. Carolina Aliaga Prof. Alzir A. Batista Prof. Otaciro R. Nascimento Prof. Héctor D. Abruña Prof. Izaura C. N. Diógenes 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(29):10081-10089
Coordination compounds of copper have been invoked as major actors in processes involving the reduction of molecular oxygen, mostly with the generation of radical species the assignment for which has, so far, not been fully addressed. In the present work, we have carried out studies in solution and on surfaces to gain insights into the nature of the radical oxygen species (ROS) generated by a copper(II) coordination compound containing a thioether clip‐phen derivative, 1,3‐bis(1,10‐phenanthrolin‐2‐yloxy)‐N‐(4‐(methylthio)benzylidene)propan‐2‐amine (2CP‐Bz‐SMe), enabling its adsorption/immobilization to gold surfaces. Whereas surface plasmon resonance (SPR) and electrochemistry of the adsorbed complex indicated the formation of a dimeric CuI intermediate containing molecular oxygen as a bridging ligand, scanning electrochemical microscopy (SECM) and nuclease assays pointed to the generation of a ROS species. Electron paramagnetic resonance (EPR) data reinforced such conclusions, indicating that radical production was dependent on the amount of oxygen and H2O2, thus pointing to a mechanism involving a Fenton‐like reaction that results in the production of OH.. 相似文献
3.
Tércio de Freitas Paulo Solange de Oliveira Pinheiro Maria Aparecida S. Da Silva Luiz Gonzaga de França Lopes Lucidalva S. Pinheiro Gil F. A. Aquino Márcia Laudelina Arruda Temperini Pedro de Lima Neto Izaura Cirino Nogueira Diógenes 《Electroanalysis》2009,21(9):1081-1089
STM and impedance results of the self‐assembled monolayer (SAM) formed with thionicotinamide (TNA) on gold indicate the presence of defects that increase with the immersion time of the electrode in the TNA solution affecting the SAM electroactivity toward the electron transfer reaction of the cytochrome c metalloprotein and [Fe(CN)6]4? and [Ru(NH3)6]3+ complexes. It was observed that this electroactivity was also affected by the pH of the electrolyte solution. SERS and STM data indicate sulfur coordination to the surface with contribution of the NH2 group. From the dependence of the TNA surface coverage on the temperature and concentration in solution, thermodynamic parameters of adsorption were determined. 相似文献
4.
Eliana M.A. Valle Benedicto A.V. Lima Antonio G. Ferreira Fbio B. do Nascimento Victor M. Deflon Izaura C.N. Digenes Ulrich Abram Javier Ellena Eduardo E. Castellano Alzir A. Batista 《Polyhedron》2009,28(16):3473-3478
The reaction of cis-[RuCl2(P–P)(N–N)] type complexes (P–P = 1,4-bis(diphenylphosphino)butane or (1,1′-diphenylphosphino)ferrocene; N–N = 2,2′-bipyridine or 1,10-phenantroline) with monodentate ligands (L), such as 4-methylpyridine, 4-phenylpyridine and benzonitrile forms [RuCl(L)(P–P)(N–N)]+ species. Upon characterization of the isolated compounds by elemental analysis, 31P{1H} NMR and X-ray crystallography it was found out that the type of the L ligand determines its position in relation to the phosphorus atom. While pyridine derivatives like 4-methylpyridine and 4-phenylpyridine coordinate trans to the phosphorus atom, the benzonitrile ligand (bzCN), a good π acceptor, coordinates trans to the nitrogen atom. A 31P{1H} NMR experiment following the reaction of the precursor cis-[RuCl2(dppb)(phen)] with the benzonitrile ligand shows that the final position of the entering ligand in the complex is better defined as a consequence of the competitive effect between the phosphorus atom and the cyano-group from the benzonitrile moiety and not by the trans effect. In this case, the benzonitrile group is stabilized trans to one of the nitrogen atoms of the N–N ligand. A differential pulse voltammetry experiment confirms this statement. In both experiments the [RuCl(bzCN)(dppb)(phen)]PF6 species with the bzCN ligand positioned trans to a phosphorus atom of the dppb ligand was detected as an intermediate complex. 相似文献
5.
Izaura Cirino Nogueira Diógenes Francisco Carlos Nart Mônica B. P. Mello Barreto Marcia Laudelina Arruda Temperini Ícaro de Sousa Moreira 《Journal of Solid State Electrochemistry》2007,11(11):1585-1590
Surface-Enhanced Raman Scattering (SERS) spectra of [Ru(CN)5(pyS)]4− (RupyS) complex self-assembled monolayer (SAM) were obtained on gold and silver surfaces at 632.8 and 413.1 nm excitation
radiations, respectively. The bands assigned to the heme iron of the cytochrome c (cyt c) metalloprotein group were observed
by using the RupyS SAM on silver at 413.1 nm. The Surface-Enhanced Resonance Raman Scattering (SERRS) spectra of the RupyS
SAM on silver in the cyt c solution obtained at −0.2 and +0.2 V present bands at 1,365 and 1,374 cm−1 characteristic of the heme group, indicating the reduced and oxidized states of this protein, respectively. The bands observed
at 1,464, 1,504, and 1,638 cm−1 are used to confirm the redox state of cyt c. The presence of the oxidized and reduced bands in function of different applied
potential is an evidence that the protein is interacting with the modifier.
This paper is dedicated to Prof. Francisco Nart, in memoriam. 相似文献
6.
Background
It is generally believed that activation in functional magnetic resonance imaging (fMRI) is restricted to gray matter. Despite this, a number of studies have reported white matter activation, particularly when the corpus callosum is targeted using interhemispheric transfer tasks. These findings suggest that fMRI signals may not be neatly confined to gray matter tissue. In the current experiment, 4 T fMRI was employed to evaluate whether it is possible to detect white matter activation. We used an interhemispheric transfer task modelled after neurological studies of callosal disconnection. It was hypothesized that white matter activation could be detected using fMRI. 相似文献7.
Cation‐Dependent Stabilization of Electrogenerated Naphthalene Diimide Dianions in Porous Polymer Thin Films and Their Application to Electrical Energy Storage 下载免费PDF全文
Catherine R. DeBlase Kenneth Hernández‐Burgos Julian M. Rotter David J. Fortman Dieric dos S. Abreu Ronaldo A. Timm Prof. Izaura C. N. Diógenes Lauro T. Kubota Prof. Héctor D. Abruña Prof. William R. Dichtel 《Angewandte Chemie (International ed. in English)》2015,54(45):13225-13229
Porous polymer networks (PPNs) are attractive materials for capacitive energy storage because they offer high surface areas for increased double‐layer capacitance, open structures for rapid ion transport, and redox‐active moieties that enable faradaic (pseudocapacitive) energy storage. Here we demonstrate a new attractive feature of PPNs—the ability of their reduced forms (radical anions and dianions) to interact with small radii cations through synergistic interactions arising from densely packed redox‐active groups, only when prepared as thin films. When naphthalene diimides (NDIs) are incorporated into PPN films, the carbonyl groups of adjacent, electrochemically generated, NDI radical anions and dianions bind strongly to K+, Li+, and Mg2+, shifting the formal potentials of NDI’s second reduction by 120 and 460 mV for K+ and Li+‐based electrolytes, respectively. In the case of Mg2+, NDI’s two redox waves coalesce into a single two‐electron process with shifts of 240 and 710 mV, for the first and second reductions, respectively, increasing the energy density by over 20 % without changing the polymer backbone. In contrast, the formal reduction potentials of NDI derivatives in solution are identical for each electrolyte, and this effect has not been reported for NDI previously. This study illustrates the profound influence of the solid‐state structure of a polymer on its electrochemical response, which does not simply reflect the solution‐phase redox behavior of its monomers. 相似文献
8.
Paulo Tde F Diógenes IC Abruña HD 《Langmuir : the ACS journal of surfaces and colloids》2011,27(5):2052-2057
Myoglobin (Mb) has been successfully immobilized on a self-assembled monolayer (SAM) of L-cysteine (Cys) on a gold electrode, Au/Cys. The presence of a pair of well-defined and nearly reversible waves centered at ca. 0.086 V vs Ag/AgCl (pH 6.5) suggests that the native character of Mb heme Fe(III/II) redox couple has been obtained. The formal potential of Mb on Cys SAM exhibited pH-dependent variation in the pH range of 5-9 with a slope of 55 mV/pH, indicating that the electron transfer is accompanied by a single proton exchange. Thermodynamic and kinetic aspects of Mb adsorption processes on Au/Cys were studied by using voltammetric and quartz-crystal microbalance methods. The Au/Cys electrode with immobilized Mb exhibited electrocatalytic activity toward ascorbic acid (AA) oxidation with an overpotential decrease of over 400 mV and a linear dependence of current on the AA concentration from 0.5 to 5.0 mmol L(-1). 相似文献
9.
10.
Marcelo Takara Jéssica Karoline Eisenhut Izaura Yoshico Hirata Luiz Juliano Amando Siuiti Ito 《Journal of fluorescence》2009,19(6):1053-1060
We investigated three amino derivatives of ortho-aminobenzoic or anthranilic acid (o-Abz): a) 2-Amino-benzamide (AbzNH2); b) 2-Amino-N-methyl-benzamide (AbzNHCH3) and c) 2-Amino-N-N′-dimethyl-bezamide (AbzNH(CH3)2), see Scheme 1. We describe the results of ab-initio calculations on the structural characteristics of the compounds and experimental studies
about solvent effects in their absorption and steady-state and time-resolved emission properties. Ab-initio calculations showed
higher stability for the rotameric conformation in which the oxygen of carbonyl is near to the nitrogen of ortho-amino group. The derivatives present decrease in the delocalization of π electron, and absorption bands are blue shifted
compared to the parent compound absorption, the extent of the effect increasing from to Abz-NH2 to Abz-NHCH3 Abz-NH(CH3)2. Measurements performed in several solvents have shown that the the dependence of Stokes shift of the derivatives with the
orientational polarizability follows the Onsager-Lippert model for general effects of solvent. However deviation occurred
in solvents with properties of Bronsted acids, or electron acceptor characteristics, so that hydrogen bonds formed with protic
solvents predominates over intramolecular hydrogen bond. In most solvents the fluorescence decay of AbzNH2 and AbzNHCH3 was fitted to a single exponential with lifetimes around 7.0 ns and no correlation with polarity of the solvent was observed.
The fluorescence decay of AbzN(CH3)2 showed lifetimes around 2.0 ns, consistent with low quantum yield of the compound. The spectroscopic properties of the monoamino
derivative AbzNHCH3 are representative of the properties presented by Abz labelled peptides and fatty acids previously studied. 相似文献