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Electrochemical Data (electrochemical + data)
Selected AbstractsInfluence of the Protonic State of an Imidazole-Containing Ligand on the Electrochemical and Photophysical Properties of a Ruthenium(II),Polypyridine-Type ComplexCHEMISTRY - A EUROPEAN JOURNAL, Issue 29 2007Annamaria Quaranta Dr. Abstract The synthesis and characterisation of [Ru(bpy)2(PhenImHPh)]2+ where PhenImHPh represents the 2-(3,5-di- tert -butylphenyl)imidazo[4,5- f][1,10]phenanthroline ligand are described. The compounds issued from the three different protonic states of the imidazole ring [Ru(bpy)2(PhenImPh)]+ (I), [Ru(bpy)2(PhenImHPh)]2+ (II) and [Ru(bpy)2(PhenImH2Ph)]3+ (III) were isolated and spectroscopically characterised. The X-ray structures of [Ru(bpy)2(PhenImPh)](PF6),H2O,6,MeOH, [Ru(bpy)2(PhenImHPh)](NO3)2,H2O,3,MeOH and [Ru(bpy)2(PhenImH2Ph)](PF6)3, 5,H2O are reported. Electrochemical data obtained on these complexes indicate almost no potential shift for the RuIII/II redox couple. Therefore a Coulombic effect between the imidazole ring and the metal centre can be ruled out. The monooxidised forms of I and II have been characterised by EPR spectroscopy and are reminiscent of the presence of a radical species. The emission properties of the parent compound [Ru(bpy)2(PhenImHPh)]2+ were studied as a function of pH and both the lifetimes and intensities decreased upon deprotonation. Photophysical properties, investigated in the absence and presence of an electron acceptor (methylviologen), were distinctly different for the three compounds. Transient absorption features indicate that unique excited states are involved. Theoretical data obtained from DFT calculations in water on the three protonic forms are presented and discussed in the light of the experimental results. [source] Electronic Control of the Rotational Barrier in ,2 -Alkyne-1-thio ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2007Wolfram W. Seidel Abstract A family of thio-alkyne complexes [Tp,Mo(CO)(L)(BnSC2S)] {Bn = benzyl, Tp, = hydrotris(3,5-dimethylpyrazolyl)borate, L = carbonyl (2), 2,6-dimethylphenyl isocyanide (7), tert -butyl isocyanide (8), 4-(dimethylamino)pyridine (9)} was prepared by reductive removal of a benzyl group in the corresponding bis(benzylthio)acetylene complexes [Tp,Mo(CO)(L)(BnSC2SBn)](PF6) (1 -PF6, 4 -PF6, 5 -PF6 and 6 -PF6). All complexes were characterized by IR, 1H, 13C spectroscopy and cyclic voltammetry. X-ray diffraction studies of 5 -PF6, 8 and 9 were carried out. The alkyne ligand is bound symmetrically to molybdenum in 5 -PF6 and unsymmetrically in 8 and 9. The trend in the ,-acidity of ligand L is reflected in the spectroscopic and electrochemical data as well as in the molecular structures. Variable temperature 1H NMR investigations with 7, 8 and 9 disclosed that the barrier of the alkyne rotation at molybdenum decreases in the order of rising electron density at the metal center while the steric demand increases. Therefore, electronic control of the barrier by the specific character of the ligand L is evident.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis and Characterization of Mixed Phthalocyaninato and meso -Tetrakis(4-chlorophenyl)porphyrinato Triple-Decker Complexes , Revealing the Origin of Their Electronic AbsorptionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2004Xuan Sun Abstract Two series of mixed phthalocyaninato and porphyrinato rare earth(III) triple-decker complexes [M2(Pc)(TClPP)2] (1a,10a) and [M2(Pc)2(TClPP)] (1b,11b) [M = Y, La,Er except Ce and Pm; Pc = phthalocyaninate; TClPP = tetrakis(4-chlorophenyl)porphyrinate] have been prepared by treating the half-sandwich complexes [M(TClPP)(acac)] (acac = acetylacetonate), generated in situ from [M(acac)3]·nH2O and H2(TClPP), with Li2(Pc). All the triple-decker complexes have been characterized by a wide range of spectroscopic and electrochemical methods. The molecular structures of [M2(Pc)(TClPP)2] (M = Y, Ho) have also been determined, and show a symmetrical disposition of ligands, with two outer domed TClPP and one inner Pc rings. A systematic investigation of the optical and electrochemical data of these complexes has revealed the nature of the HOMO and LUMO, as well as the origin of the electronic absorptions of these triple-decker complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] A family of thioxanthato ruthenium and osmium arylsISRAEL JOURNAL OF CHEMISTRY, Issue 3 2001Swarup Chattopadhyay The title complexes of type M(RL2)(PPh3)2(CO)(S2CSEt) (2a: M = Ru; 2b: M = Os) have been synthesized in excellent yields by reacting M(RL1)(PPh3)2(CO)X (1a: M = Ru, × = Cl; 1b: M = Os, × = Br) with potassium ethyl thioxanthate and have been characterized with the help of spectral and electrochemical data. The RL2 ligand in 2 is the imine-phenol tautomer of N-C6H4R(p)-4-methylsalicylaldimine (R = Me, MeO, Cl) coordinated at the carbanionic-C2 atom only while RL1 in 1 is the iminium-phenolato tautomer chelated via carbanionic-C2 and phenolato-O atoms. The synthetic reaction is thus attended with tautomerization of the Schiff base ligand. It is also associated with a rotation of the ligand by ,180° around the M,C bond in order to exclude steric repulsion. These features have been revealed by structure determination of 2a (R = Me). The metallated aldimine ring is found to be highly noncoplanar (dihedral angle ,40°) with the thioxanthate chelate ring due to steric repulsion originating from the relatively large size of the sulfur atom. This phenomenon, which is absent in both the precursor 1 (R = Me) and in the carboxylate analogue Ru(MeL2)(PPh3)2(CO)(O2CMe), 7, has distinctive effects on bond parameters of 2a (R = Me). Thus the two Ru,P bonds in 2a (R = Me) differ in length by as much as 0.06 Å. The thioxanthate 2 is thermodynamically more stable than the precursor 1 as well as the carboxylate 7. Accordingly, both of these are irreversibly transformed to 2a (R = Me) upon treatment with thioxanthate. [source] Optical and electrochemical properties of copoly(aryl ether)s consisting of alternate 2,5-distyrylbenzene and electron-transporting oxadiazole or triazole derivativesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2005Shinn-Horng Chen Abstract New copoly(aryl ether) P1 consisting of alternate electron-transporting 2-(3-(trifluoromethyl)phenyl)-5-(4-(5-(3-(trifluoromethyl)phenyl)-1,3,4-oxadiazol-2-yl)-2,5-bis(hexyloxy)phenyl)-1,3,4-oxadiazole and hole-transporting 2,5-distyrylbenzene (DSB) was synthesized via nucleophilic substitution polymerization. We investigated the optical and electrochemical properties of alternate copoly(aryl ether)s P1,P6, which contain the same hole-transporting DSB segments, but with different electron transporting segments. The effect of trifluoromethyl groups in electron transporting segments is also discussed. Referencing to the spectra of their model compounds M1,M4, the emissions of P1,P3 are dominated exclusively by the hole-transporting fluorophores with longer emissive wavelength about 452,453 nm via efficient excitation energy transfer. Furthermore, P1,P3 also exhibit unique variations in energy transfer in acidic media and solvatochromism in organic solvents. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of P1,P4, estimated from electrochemical data, are ,5.12, ,5.15, ,5.18, ,5.00 eV and ,2.93, ,3.39, ,3.49, ,2.76 eV, respectively. The electron and hole affinity of P1,P6 can be enhanced simultaneously by introducing isolated hole- and electron-transporting segments in backbone. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5083,5096, 2005 [source] Multilayer Thin Films by Layer-by-Layer Assembly of Hole- and Electron-Transport Polyelectrolytes: Optical and Electrochemical PropertiesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 20 2006Kyungsun Choi Abstract Summary: In this paper, we present the synthesis of a series of p-type and n-type semiconducting polyelectrolytes with triarylamine, oxadiazole, thiadiazole and triazine moieties. The synthesized polymeric hole and electron transport materials were examined optically and electrochemically using UV/Vis spectroscopy, PL spectroscopy and CV. Based on the optical and electrochemical data, each of the energy levels were calculated and all values suggested that they were promising hole- (p-type) or electron-transport (n-type) materials for devices. Moreover, the synthesized ionic polymers were suitable for LBL thin film deposition from dilute polymer solutions and the multilayers were fully characterized by UV/Vis, PL spectroscopy and CV. [source] Molecular Dynamics Simulations of the Orientation and Reorientational Dynamics of Water and Polypyrrole Rings as a Function of the Oxidation State of the PolymerMACROMOLECULAR THEORY AND SIMULATIONS, Issue 1 2005Jose J. López Cascales Abstract Summary: Polypyrrole is one of the most widely-studied conducting polymers due to its steady electrochemical response and good chemical stability in different solvents, including organic and inorganic ones. In this work, we provide for the first time valuable information in atomic detail concerning the steady and dynamic properties of pyrrole rings as a function of the oxidation state of the polymer. The study was carried out by Classical molecular dynamics simulation, where the system was modelled by 256 polypyrrole chains of 10 pyrrole rings each. Water was explicitly introduced in our simulations. Besides the uncharged or reduced state, two steady oxidation states of the polymer have been simulated by introducing a net charge (+1) on 85 and 256 of the polypyrrole chains. To balance the charges emerging in these oxidised states, 85 and 256 chloride ions (Cl,1) respectively, were introduced into the system. From an analysis of the simulated trajectories, the orientation and relaxation times of water and pyrrole rings were evaluated for the different oxidation states of the polymer across the polypyrrole/water interface. The calculated densities for different oxidation states describe the swelling or shrinking process during electrochemical oxidation or reduction respectively. The rotational relaxation times calculated for the polypyrrole rings decrease with increasing oxidation of the polymer, which is in a good agreement with experimental electrochemical data. Almost no variation in pyrrole ring orientation was measured for the different oxidation states of the polymer, even compared with polypyrrole bulk. As regards the water structure in the vicinity of the polypyrrole/water interface, both the orientation and orientation relaxation time were strongly affected by the presence of charges in the polymer. Thus, the water dipole was strongly orientated in the vicinity of the water/polypyrrole interface and its orientational relaxation time increased by one order of magnitude compared with bulk water, even when only one-third of the total polymer chains were oxidised. The results attained in this work were validated with experimental results, when they were available. Polypyrrole ring orientation and water orientation at the polypyrrole/water interface. (a) 256 rPPy and (b)171 rPPy,+,85 oPPy. [source] Synthesis, characterization, electrochemical, catalytic and antimicrobial activity studies of hydrazone Schiff base ruthenium(II) complexesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2010N. Thilagavathi Abstract Four tridentate O, N, O donor Schiff base ligands were prepared by the reaction of substituted benzhydrazide and appropriate salicylaldehyde. The complexes of these ligands were synthesized by refluxing the ligands with ruthenium(II) starting complexes of the formula [RuHCl(CO)(EPh3)2B] in benzene, where E = P or As; B = PPh3 or AsPh3 or pyridine. The newly synthesized complexes were characterized by elemental, spectral (FT-IR, UV and NMR) and electrochemical data. On the basis of the above studies, an octahedral structure has been proposed for all the complexes. The catalytic efficiency of the complexes in aryl,aryl couplings and oxidation of alcohols was examined and their inhibition activity against the growth of the micro-organisms was also examined. Copyright © 2009 John Wiley & Sons, Ltd. [source] CORRELATION BETWEEN SPECTRAL, SEM/EDX AND ELECTROCHEMICAL PROPERTIES OF MAYA BLUE: A CHEMOMETRIC STUDY*ARCHAEOMETRY, Issue 6 2009A. DOMÉNECH Visible spectra, composition from SEM/EDX and solid-state electrochemical data are correlated for a set of 12 Maya Blue samples from different archaeological sites of Campeche and Yucatán (Mexico). In addition to indigo and dehydroindigo, indirubin and other possibly indigo-type compounds can be detected in Maya Blue samples. Application of hierarchical cluster analysis techniques allows similarity relationships to be established between samples from different sites, confirming prior results which suggest that the preparation of Maya Blue pigment evolved with time during the Maya culture following a ramified scheme. [source] Single-Step Electron Transfer on the Nanometer Scale: Ultra-Fast Charge Shift in Strongly Coupled Zinc Porphyrin,Gold Porphyrin DyadsCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2008Jérôme Fortage Dr. Abstract The synthesis, electrochemical properties, and photoinduced electron transfer processes of a series of three novel zinc(II),gold(III) bisporphyrin dyads (ZnPSAuP+) are described. The systems studied consist of two trisaryl porphyrins connected directly in the meso position via an alkyne unit to tert -(phenylenethynylene) or penta(phenylenethynylene) spacers. In these dyads, the estimated center to center interporphyrin separation distance varies from 32 to 45,Å. The absorption, emission, and electrochemical data indicate that there are strong electronic interactions between the linked elements, thanks to the direct attachment of the spacer on the porphyrin ring through the alkyne unit. At room temperature in toluene, light excitation of the zinc porphyrin results in almost quantitative formation of the charge shifted state .+ZnPSAuP., whose lifetime is in the order of hundreds of picoseconds. In this solvent, the charge-separated state decays to the ground state through the intermediate population of the zinc porphyrin triplet excited state. Excitation of the gold porphyrin leads instead to rapid energy transfer to the triplet ZnP. In dichloromethane the charge shift reactions are even faster, with time constants down to 2,ps, and may be induced also by excitation of the gold porphyrin. In this latter solvent, the longest charge-shifted lifetime (,=2.3,ns) was obtained with the penta-(phenylenethynylene) spacer. The charge shift reactions are discussed in terms of bridge-mediated super-exchange mechanisms as electron or hole transfer. These new bis-porphyrin arrays, with strong electronic coupling, represent interesting molecular systems in which extremely fast and efficient long-range photoinduced charge shift occurs over a long distance. The rate constants are two to three orders of magnitude larger than for corresponding ZnPAuP+ dyads linked via meso -phenyl groups to oligo-phenyleneethynylene spacers. This study demonstrates the critical impact of the attachment position of the spacer on the porphyrin on the electron transfer rate, and this strategy can represent a useful approach to develop molecular photonic devices for long-range charge separations. [source] | |||||||||||||