1,721,356 research outputs found
Is the Herfindahl Index a reliable indicator for measuring hospital competition? An empirical study
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Measuring two effects of Phisician-Population ratio: A perspective from macro-level model
No full textQuality Competition Among Hospitals: The Effects of Perceived Quality and Perceived Expensiveness on Healthcare Consumers
No full textPatient satisfaction with and recommendation of a hospital: effects of interpersonal and technical aspects of hospital care
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Electrocatalytic oxidation of styrene by a high valent ruthenium porphyrin cation radical
No full text[[abstract]]A sterically-hindered carbonylruthenium(II) porphyrin Ru-II(CO)(TMP) (where TMP = meso-tetramesitylporphyrinato dianion) has been synthesized. Chemical oxidation of Ru-II(CO)(TMP) by m-chloroperbenzoic acid (m-CPBA) gives the dioxoruthenium(VI) porphyrin (Ru-VI(O)(2)TMP). Cyclic voltammograms show that Ru-VI(O)(2)TMP is reversibly oxidized at E-1/2 = +1.24 V in CH2Cl2. Thin-layer absorption spectra for oxidation of Ru-VI(O)(2)TMP at + 1.32 V indicates that the product is a porphyrin cation radical (Ru-VI(O)(2)TMP+.). Electrogenerated Ru-VI(O)(2)TMP+. reacts selectively with styrene to give phenylacetaldehyde (96%) and benzaldehyde (4%). We report the first case of styrene oxidation by high valent ruthenium porphyrin under electrochemical conditions. An electrocatalytic oxidation reaction scheme is proposed. (C) 2000 Elsevier Science S.A. All rights reserved.[[note]]SC
Substituent and axial ligand effects on the electrochemistry of zinc porphyrins
No full text[[abstract]]An absorption spectral and electrochemical study for the zinc(II) complexes of meso-tetraphenylporphyrin dianion (TPP), mesotetramesitylporphyrin dianion (TMP) and meso-tetra(2,6-dichlorophenyl)porphyrin dianion (TDCPP) in the presence of nitrogeneous bases in CH2Cl2 solution is reported. The Soret and Q bands of the zinc porphyrins were red-shifted in the presence of imidazole bases, however, the formation constants (K-f) with imidazole or 2-methylimidazole titration were found to be of a similar magnitude. The K-f and the formal electrode potentials of zinc porphyrins are in agreement with the electron-donating-withdrawing properties of the substituents in the phenyl groups. K-f for complexation of the imidazole to the oxidized and reduced zinc porphyrins was obtained from the electrochemical study. The one-electron oxidation of zinc porphyrins showed greater affinity toward imidazole ligation than the other oxidation states of zinc porphyrins. ZnTDCPP+. was found to have the greatest affinity with K-f up to 1.35 x 10(8). Spectroelectrochemical methods were used to obtain absorption spectra of the complexation of zinc porphyrin cation radical with imidazole. The results showed a slight spectral difference between the complexed and uncomplexed zinc porphyrin cation radical. (C) 2002 Published by Elsevier Science B.V.[[note]]SC
Spectral and electrochemical studies of axial ligand binding reactions of carbonylruthenium(II) meso-tetramesitylporphyrin
No full text[[abstract]]The spectral and electrochemical properties of carbonylruthenium(II) meso-tetramesitylporphyrin, Ru(CO)(TMP) in the presence of imidazole, N-methylimidazole and hydroxide anion as axial ligands were investigated. Spectrophotometric titration of Ru(CO)(TMP) of the nitrogeneous bases caused the absorption spectrum to shift to longer wavelengths. Larger shifts in wavelength were observed in the titration using tetrabutylammonium hydroxide. The formation constants for these ligands coordinated to the ruthenium center were calculated. The effect of axial ligand ligation caused the decrease of vibrational frequency of CO as detected from FT-IR spectroscopy. The CO stretching frequency (nu(CO)) of Ru(CO)TMP in CH2Cl2 is 1940 cm(-1) which is lowered to 1936 and 1913 cm(-1) upon coordination of nitrogenous bases and hydroxide anion, respectively. Cyclic voltammetry of Ru(CO)(TMP) in CH2Cl2 showed an irreversible reduction wave at -1.63 V and two reversible oxidations at E-1/2 = 0.78 and 1.27 V vs. Ag vertical bar AgCl, respectively. Addition of imidazole and hydroxide into Ru(CO)(TMP) solution caused shifts in the redox potential and accordingly, the binding constants of the ligands to the one- and two-electron oxidized ruthenium porphyrins were estimated and compared. Spectroelectrochemical methods were used to characterize the above electron-transfer reactions. (c) 2004 Elsevier B.V. All rights reserved.[[note]]SC
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