Involvement of a Binuclear Species with the Re−C(O)O−Re Moiety in CO_2 Reduction Catalyzed by Tricarbonyl Rhenium(I) Complexes with Diimine Ligands: Strikingly Slow Formation of the Re−Re and Re−C(O)O−Re Species from Re(dmb)(CO)_3S (dmb = 4,4‘-Dimethyl-2,2‘-bipyridine, S = Solvent)

Excited-state properties of fac-[Re(dmb)(CO)_3(CH_3CN)]PF_6, [Re(dmb)(CO)_3]_2 (where dmb = 4,4‘-dimethyl-2,2‘-bipyridine), and other tricarbonyl rhenium(I) complexes were investigated by transient FTIR and UV−vis spectroscopy in CH_3CN or THF. The one-electron reduced monomer, Re(dmb)(CO)_3S (S = CH_3CN or THF), can be prepared either by reductive quenching of the excited states of fac-[Re(dmb)(CO)_3(CH_3CN)]PF_6 or by homolysis of [Re(dmb)(CO)_3]_2. In the reduced monomer's ground state, the odd electron resides on the dmb ligand rather than on the metal center. Re(dmb)(CO)_3S dimerizes slowly in THF, k_d = 40 ± 5 M^(-1) s^(-1). This rate constant is much smaller than those of other organometallic radicals which are typically 10^9 M^(-1) s^(-1). The slower rate suggests that the equilibrium between the ligand-centered and metal-centered radicals is very unfavorable (K ≈ 10^(-4)). The reaction of Re(dmb)(CO)_3S with CO_2 is slow and competes with the dimerization. Photolysis of [Re(dmb)(CO)_3]_2 in the presence of CO_2 produces CO with a 25−50% yield based on [Re]. A CO_2 bridged dimer, (CO)_3(dmb)Re−CO(O)−Re(dmb)(CO)_3 is identified as an intermediate. Both [Re(dmb)(CO)_3]_2(OCO_2) and Re(dmb)(CO)_3(OC(O)OH) are detected as oxidation products; however, the previously reported formato-rhenium species is not detected

Characteristics of acute congestive heart failure with normal ejection fraction and less elevated B-type natriuretic peptide

Abstract Background Heterogeneity in B-type natriuretic peptide (BNP) levels, especially among individuals with acute heart failure with normal left ventricular ejection fraction (HFNEF), can cause confusion in interpreting results. We investigated the characteristics of cases of acute HFNEF with only modestly elevated BNP. Methods One hundred forty-two patients with acute or acute exacerbation of chronic HFNEF were divided into two groups by BNP level: BNP Results In the NB group, a history of open-heart surgery (OHS) was more frequent (71% vs. 22%, p Conclusion We found associations between acute HFNEF with less elevated BNP and a history of OHS. In a patient suspected of HFNEF, a history of OHS is considered diagnostic evidence of presence of diastolic heart failure when plasma levels of BNP are less elevated.</p

Prevalence and characteristics of myocardial crypts in Japanese patients referred for cardiovascular magnetic resonance

18th Annual SCMR Scientific SessionsNice, France. 4-7 February 201

Prevalence and characteristics of myocardial crypts in Japanese patients referred for cardiovascular magnetic resonance

18th Annual SCMR Scientific Sessions Nice, France. 4-7 February 201

Visible light-driven H2 production over highly dispersed Ruthenia on Rutile TiO2 nanorods

The immobilization of miniscule quantities of RuO2 (~0.1%) onto one-dimensional (1D) TiO2 nanorods (NRs) allows H2 evolution from water under visible light irradiation. Rod-like rutile TiO2 structures, exposing preferentially (110) surfaces, are shown to be critical for the deposition of RuO2 to enable photocatalytic activity in the visible region. The superior performance is rationalized on the basis of fundamental experimental studies and theoretical calculations, demonstrating that RuO2(110) grown as 1D nanowires on rutile TiO2(110), which occurs only at extremely low loads of RuO2, leads to the formation of a heterointerface that efficiently adsorbs visible light. The surface defects, band gap narrowing, visible photoresponse, and favorable upward band bending at the heterointerface drastically facilitate the transfer and separation of photogenerated charge carriers.Peer ReviewedPostprint (published version

Theoretical Modeling of Low-Energy Electronic Absorption Bands in Reduced Cobaloximes

The reduced Co^I states of cobaloximes are powerful nucleophiles that play an important role in the hydrogen-evolving catalytic activity of these species. In this work we analyze the low-energy electronic absorption bands of two cobaloxime systems experimentally and use a variety of density functional theory and molecular orbital ab initio quantum chemical approaches. Overall we find a reasonable qualitative understanding of the electronic excitation spectra of these compounds but show that obtaining quantitative results remains a challenging task

Transition State Characterization for the Reversible Binding of Dihydrogen to Bis(2,2'-bipyridine)rhodium(I) from Temperature- and Pressure-Dependent Experimental and Theoretical Studies

Thermodynamic and kinetic parameters for the oxidative addition of H_2 to [Rh^I(bpy)_2]^+ (bpy = 2,2‘-bipyridine) to form [Rh^(III)(H)_2(bpy)_2]^+ were determined from either the UV−vis spectrum of equilibrium mixtures of [Rh^I(bpy)_2]^+ and [Rh^(III)(H)_2(bpy)_2]^+ or from the observed rates of dihydride formation following visible-light irradiation of solutions containing [Rh^(III)(H)_2(bpy)_2]^+ as a function of H_2 concentration, temperature, and pressure in acetone and methanol. The activation enthalpy and entropy in methanol are 10.0 kcal mol^(-1) and −18 cal mol^(-1) K^(-1), respectively. The reaction enthalpy and entropy are −10.3 kcal mol^(-1) and −19 cal mol^(-1) K^(-1), respectively. Similar values were obtained in acetone. Surprisingly, the volumes of activation for dihydride formation (−15 and −16 cm^3 mol^(-1) in methanol and acetone, respectively) are very close to the overall reaction volumes (−15 cm^3 mol^(-1) in both solvents). Thus, the volumes of activation for the reverse reaction, elimination of dihydrogen from the dihydrido complex, are approximately zero. B3LYP hybrid DFT calculations of the transition-state complex in methanol and similar MP2 calculations in the gas phase suggest that the dihydrogen has a short H−H bond (0.823 and 0.810 Å, respectively) and forms only a weak Rh−H bond (1.866 and 1.915 Å, respectively). Equal partial molar volumes of the dihydrogenrhodium(I) transition state and dihydridorhodium(III) can account for the experimental volume profile found for the overall process

Coping behaviors with the experience of outpatients with gynecological cancer during adjuvant chemotherapy

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Nursing practice of advanced care planning for terminal cancer patients by general ward nurses

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