A mononuclear Cu II complex acts as an efficient catalyst for four-electron reduction of O 2 to H 2 O by a ferrocene derivative via formation of the dinuclear Cu II peroxo complex that is further reduced in the presence of protons by a ferrocene derivative to regenerate the Cu II complex.Cytochrome c oxidases (CcOs), with a bimetallic active-site consisting of a heme a and Cu (Fe a3 /Cu B ), are the terminal enzymes of respiratory chains, catalyzing the reduction of molecular oxygen to water by the soluble electron carrier, cytochrome c. 1,2 Synthetic Fe a3 / Cu B analogs have attracted significant attention, because the four-electron reduction of O 2 is not only of great biological interest,3 , 4 but also of technological significance such as in fuel cells.5 ,6 Multicopper oxidases such as laccase also activate oxygen at a site containing a threeplus-one arrangement of 4 Cu atoms, exhibiting remarkable electroactivity for the four-electron reduction of oxygen at potentials approaching 1.2 V (vs RHE). 7 Such electrocatalytic reduction of O 2 has frequently been used to probe the catalytic reactivity of synthetic CcO model complexes3 -5 and some copper (only) complexes have also been investigated. 8-10 However, there has been no report on the copper complex catalyzed four-electron reduction of O 2 employing one-electron reductants in homogeneous solution; such situations are amenable to systematic studies which provide considerable mechanistic insights. 11 fukuzumi@chem.eng.osaka-u.ac.jp, karlin@jhu.edu. Supporting Information Available. Experimental section, kinetic analysis, and figures ( Figure S1-S7). This material is available free of charge via the Internet at http://pubs.acs.org. Figure S1). It has also been confirmed that no H 2 O 2 is detected via iodometric titration experiments ( Figure S2 Figure S3). 14 Thus, the stoichiometry of the catalytic reduction of O 2 by Fc * is given by eq 1. 15 NIH Public AccessThe time profile of the four-electron reduction of O 2 with Fc * catalyzed by 1 in the presence of HClO 4 in acetone at 298 K was examined by stopped-flow measurements. Figure 2a shows the observed absorption spectral change during the catalytic reaction. Under the conditions employed with relative concentrations of reagents as given in the Figure 2 caption, it is only after Fc *+ (λ max = 780 nm) is completely formed that the peroxo species, [(tmpa)Cu II (O 2 ) Cu II (tmpa)] 2+ (2: λ max = 520 nm) 16 starts to be produced. 17 This is more clearly seen in Figure 2b, the time profiles for the absorbance at 780 nm due to Fc *+ , by comparison to the absorbance at 520 nm due to 2. The rate of formation of Fc *+ in Figure 2b appears to be constant with respect to the concentration of Fc *+ , when the concentration of Fc * is in large excess compared to that of HClO 4 . The constant rate (M s −1 ) increases linearly with increasing concentration of 1 and Fc * ( Figure S5). The second-order rate constant (k obs ) is determined to be (1.1 ± 0.1) × 10 5 M −1 s −1 from the slope of Figure S5, which ...

A simple donor-acceptor linked dyad, 9-mesityl-10-methylacridinium ion (Acr þ -Mes) was incorporated into nanosized mesoporous silica-alumina to form a composite, which in acetonitrile is highly dispersed. In this medium, upon visible light irradiation, the formation of an extremely long-lived electron-transfer state (Acr • -Mes •þ ) was confirmed by EPR and laser flash photolysis spectroscopic methods. The composite of Acr þ -Mes-incorporated mesoporous silica-alumina with an added copper complex [ðtmpaÞCu II ]ðClO 4 − Þ 2 (tmpa ¼ trisð2-pyridylmethylÞamine) acts as an efficient and robust photocatalyst for the selective oxygenation of p-xylene by molecular oxygen to produce p-tolualdehyde and hydrogen peroxide. Thus, incorporation of Acr þ -Mes into nanosized mesoporous silica-alumina combined with an O 2 -reduction catalyst (½ðtmpaÞCu II 2þ ) provides a promising method in the development of efficient and robust organic photocatalysts for substrate oxygenation by dioxygen, the ultimate environmentally benign oxidant.copper complex catalyst | donor-acceptor dyad | nanosized silica-alumina | p-xylene | photoinduced electron transfer

Background: Intravenous myocardial contrast echocardiography (MCE) at rest and during vasodilator stress is a reliable bedside technique for assessment of myocardial perfusion in patients with coronary artery disease. The aim of this study is to evaluate diagnostic accuracy of myocardial perfusion abnormalities using MCE at rest in patients with acute coronary syndrome (ACS). This study is the first MCE multicenter trial for the evaluation of ACS in Japan. Methods: We performed triggered MCE at rest in 102 patients (mean age: 65 ± 11 years) with suspected ACS. We obtained 1:1 and 1:6 end-systolic triggered MCE images at four- and two-chamber views. We detected myocardial ischemia by the appearance of myocardial perfusion abnormalities (defect or reduction) in 1:1 end-systolic triggered MCE image. We assessed the appearance of regional wall motion abnormality (RWMA) at the same time. Quantitative coronary angiography was performed in all patients within 1 week (2.6 ± 2.2 days) after MCE. Results: Eighty-four of 102 (82%) patients were diagnosed ACS (unstable angina: 70 patients; non-ST-segment elevation myocardial infarction: 11 patients; ST-segment elevation myocardial infarction: 3 patients) and demonstrated significant coronary artery stenosis (stenosis = or >75%) that required coronary revascularization therapy. The sensitivity, specificity, and accuracy of myocardial perfusion abnormality by MCE at rest for diagnosing ACS were 79%, 86%, and 83%, respectively. On each coronary artery, the sensitivity, specificity, and accuracy of MCE for diagnosing ACS were 85%, 71%, and 79% in the left anterior descending artery; 70%, 92%, and 84% in the left circumflex artery; 77%, 89%, and 84% in the right coronary artery, respectively. The sensitivity, specificity, and accuracy of RWMA for diagnosing ACS were 49%, 90%, and 71%, respectively, and the sensitivity of MCE for diagnosing ACS was significantly higher than that of RWMA. Conclusion: Intravenous myocardial contrast echocardiography at rest without stress examination is a feasible noninvasive method for accurate diagnosis of ACS. In this multicenter study, MCE at rest improved the diagnostic accuracy of echocardiography for diagnosing ACS.

Several cobalt(III) complexes of the [Co(apS or apSe)(N4)]2+ type were prepared, where apS and apSe denote chiral 1-amino-2-propanethiolate-N,S and 1-amino-2-propaneselenolate-N,Se ligands, respectively, and N4 is (en=ethylenediamine)2, (R-chxn=(R,R)-1,2-cyclohexanediamine)2, or tren=tris(2-aminoethyl)amine. Their circular dichroism (CD) spectra were compared with one another and with those of complexes containing such ligands as achiral 2-aminoethanethiolate-N,S, 2-aminoethaneselenolate-N,Se or chiral 1-amino-2-propanolate-N,O (apO). The vicinal CD curves of S-apS obtained from CD spectra of the en and R-chxn complexes are similar and very large in magnitude in the d-d absorption band region. These curves are very similar to the CD spectrum of [Co(S-apO)(NH3)4]2+. The vicinal CD curve of S-apSe shows a similar pattern, but the magnitude is smaller than those of the S-apS and S-apO ligands. The vicinal effect of the protonated S-apSH ligand is much smaller compared with that of its conjugate base (S-apS) ligand. The tren complexes of S-apS and S-apSe exhibit CD spectra fairly different from the vicinal CD curves of the respective ligands in the d-d absorption band region.