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Charge Transfer (charge + transfer)
Kinds of Charge Transfer Terms modified by Charge Transfer Selected AbstractsImpact of Ground-State Charge Transfer and Polarization Energy Change on Energy Band Offsets at Donor/Acceptor Interface in Organic PhotovoltaicsADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Kouki Akaike Abstract The fullerene (C60)/copper phthalocyanine (CuPc) interface is one of the widely used donor/acceptor (DA) interfaces for organic photovoltaics (OPVs), and information on the electronic structure at the interface is essential for fully understanding the energetics of excitons and carriers in OPVs. Here, an investigation into the energy levels at the C60/CuPc interface is made using UV photoelectron, X-ray photoelectron, and inverse photoemission spectroscopies. The vacuum level and core levels rise with C60 deposition on the CuPc film, which indicates that the interfacial dipole is formed with the negative charge on the C60 side. The interfacial dipole can be formed by the electron transfer from CuPc to C60 in the ground state at the interface, which is indicated by the analysis of the UV,vis,NIR absorption spectrum of the CuPc/C60 blended film. On the other hand, the highest occupied and lowest unoccupied molecular orbitals of CuPc and C60 shift in opposite directions at the interface. This is attributed to the changes of the polarization energies of CuPc and C60 at the interface. The formation of the interfacial dipole and the change of the polarization energy result in the anomalous energy band offsets at the C60/CuPc interface, which are entirely different from those in inorganic p,n junctions. [source] Photo-induced Charge Transfer and Relaxation of Persistent Charge Carriers in Polymer/Nanocrystal Composites for Applications in Hybrid Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 23 2009Marc Daniel Heinemann Abstract The photo-induced charge transfer and the dynamics of persistent charge carriers in blends of semiconducting polymers and nanocrystals are investigated. Regioregular poly(3-hexylthiophene) (P3HT) is used as the electron donor material, while the acceptor moiety is established by CdSe nanocrystals (nc-CdSe) prepared via colloidal synthesis. As a reference system, organic blends of P3HT and [6,6]-phenyl C61 -butyric acid methyl ester (PCBM) are studied as well. The light-induced charge transfer between P3HT and the acceptor materials is studied by photoluminescence (PL), photo-induced absorption (PIA) and light-induced electron spin resonance spectroscopy (LESR). Compared to neat P3HT samples, both systems show an intensified formation of polarons in the polymer upon photo-excitation, pointing out successful separation of photogenerated charge carriers. Additionally, relaxation of the persistent charge carriers is investigated, and significant differences are found between the hybrid composite and the purely organic system. While relaxation, reflected in the transient signal decay of the polaron signal, is fast in the organic system, the hybrid blends exhibit long-term persistence. The appearance of a second, slow recombination channel indicates the existence of deep trap states in the hybrid system, which leads to the capture of a large fraction of charge carriers. A change of polymer conformation due to the presence of nc-CdSe is revealed by low temperature LESR measurements and microwave saturation techniques. The impact of the different recombination behavior on the photovoltaic efficiency of both systems is discussed. [source] Monitoring the Channel Formation in Organic Field-Effect Transistors via Photoinduced Charge TransferADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Thokchom Birendra Singh Abstract Conducting channel formation in organic field-effect transistors (OFETs) is considered to happen in the organic semiconductor layer very close to the interface with the gate dielectric. In the gradual channel approximation, the local density of accumulated charge carriers varies as a result of applied gate bias, with the majority of the charge carriers being localized in the first few semiconductor monolayers close to the dielectric interface. In this report, a new concept is employed which enables the accumulation of charge carriers in the channel by photoinduced charge transfer. An OFET employing C60 as a semiconductor and divinyltetramethyldisiloxane-bis(benzocyclobutene) as the gate dielectric is modified by a very thin noncontinuous layer of zinc-phthalocyanine (ZnPc) at the semiconductor/dielectric interface. With this device geometry, it is possible to excite the phthalocyanine selectively and photogenerate charges directly at the semiconductor/dielectric interface via photoinduced electron transfer from ZnPc onto C60. Thus the formation of a gate induced and a photoinduced channel in the same device can be correlated. [source] A Triphenylamine Dye Model for the Study of Intramolecular Energy Transfer and Charge Transfer in Dye-Sensitized Solar Cells,ADVANCED FUNCTIONAL MATERIALS, Issue 21 2008Haining Tian Abstract A novel dye (2TPA-R), containing two triphenylamine (TPA) units connected by a vinyl group and rhodanine-3-acetic acid as the electron acceptor, is designed and synthesized successfully to reveal the working principles of organic dye in dye-sensitized solar cells (DSSCs). 2TPA and TPA-R, which consist of two TPA units connected by vinyl and a TPA unit linked with rhodanine-3-acetic acid, respectively, are also synthesized as references to study the intramolecular energy transfer (EnT) and charge transfer (ICT) processes of 2TPA-R in CH2Cl2 solution and on a TiO2 surface. The results suggest that the intramolecular EnT and ICT processes show a positive effect on the performance of DSSCs. However, the flexible structure and less-adsorbed amount of dye on TiO2 may make it difficult to improve the efficiency of DSSCs. This study on intramolecular EnT and ICT processes acts as a guide for the design and synthesis of efficient organic dyes in the future. [source] Light-Induced Charge Transfer in Pyrene/CdSe-SWNT Hybrids,ADVANCED MATERIALS, Issue 5 2008L. Hu Hybrids of pyrene/CdSe-single-walled carbon nanotubes (SWNTs) are fabricated by self-assembling surface-functionalized pyrene/CdSe nanoparticles onto CVD-grown SWNTs. Light- induced charge transfer from the nanoparticles to the nanotubes is determined from the threshold voltage shift of a SWNT field-effect transistor, yielding a maximum value of 2.2 electrons per pyrene/CdSe nanoparticle. [source] The Use of Charge Transfer to Enhance the Methane-Storage Capacity of Single-Walled, Nanostructured Carbon,ADVANCED MATERIALS, Issue 17 2004K. Murata The Figure illustrates methane densities adsorbed at 303,K and 3.5,MPa in pores of lanthanide-nitrate-dispersed, single-walled carbon nanohorns (SWNHs). For reference, bulk methane density and methane density adsorbed in pores of as-grown SWNH are also depicted. A small amount of lanthanide-nitrate dispersion (0.1,mmol lanthanide nitrate per gram of SWNH) has been shown to strongly enhance methane adsorption. [source] The ,-Accepting Arene HAT(CN)6 as a Halide Receptor through Charge Transfer: Multisite Anion Interactions and Self-Assembly in Solution and the Solid State,ANGEWANDTE CHEMIE, Issue 40 2010Dr. Helen T. Chifotides Sensibles Selbstorganisat: Ihre außergewöhnliche ,-Elektronenakzeptorstärke macht die Titelverbindung zu einem exzellenten kolorimetischen Halogenidsensor. Neu daran ist, dass HAT(CN)6 mit Anionen multiple Wechselwirkungen (sowohl Charge-Transfer als auch Anion-,) in Lösung und im Festkörper eingeht. Die Halogenidionen bewirken die spontane Selbstorganisation der Sandwichkomplexe über ,2,,2 -Ladungstransferkontakte. [source] Synthesis of Ideal AM-6 and Elucidation of V4+ -to-O Charge Transfer in Vanadate Quantum Wires,ANGEWANDTE CHEMIE, Issue 29 2010Jit Datta, Shuvo Der Vanadosilicat-Zeolith AM-6 mit einer dreidimensionalen Anordnung von Vanadat(VIVO32,)-Quantendrähten (siehe Bild) wurde in Form hochwertiger Kristalle (frei von VV, Titanosilicat-Kristallkeimen und organischen Templatkationen in den Poren) aus preiswertem V2O5 hergestellt. Die lineare Abhängigkeit von ,max und der Bandlückenenergie Eg von der Partialladung der O-Atome zeigt, dass die UV-Bande von AM-6 auf einen Metall-Ligand-Ladungstransfer von VIV zu O zurückgeht. [source] An Unprecedented Charge Transfer Induced Spin Transition in an Fe,Os Cluster,ANGEWANDTE CHEMIE, Issue 8 2010Matthew Immer im Kreis herum: Der neuartige Komplex {[Fe(tmphen)2]3[Os(CN)6]2} (siehe Struktur) ist der erste Cluster, in dem sich ein High-Spin-FeIII -Ion in einer Koordinationsumgebung von vier Imin-Stickstoffdonoren und zwei N-koordinierten Cyaniden befindet. Magnetische Messungen offenbaren einen beispiellosen reversiblen ladungstransferinduzierten Spinübergang (CTIST) zwischen Low-Spin-FeII -NC-OsIII und High-Spin-FeIII -NC-OsII. [source] Charge Transfer Assisted by Collective Hydrogen-Bonding Dynamics,ANGEWANDTE CHEMIE, Issue 34 2009Bipolare Fehlordnung: Femtosekunden-Spektroskopie an Proben in protischen und aprotischen Lösungsmitteln ähnlicher Polarität ergab, dass Charge-Transfer-Prozesse durch die Bildung von Solut-Solvens-Wasserstoffbrückennetzwerken erheblich erleichtert werden (siehe Bild). Solche molekülspezifischen Wechselwirkungen kommen in den Kontinuums-Dielektrizitätsmodellen der Solvatisierung nicht vor und sollten beispielsweise bei Enzymprozessen von Bedeutung sein. [source] ChemInform Abstract: Intermetallic Charge Transfer in A-Site-Ordered Double Perovskite BiCu3Fe4O12.CHEMINFORM, Issue 47 2009Youwen Long Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Charge Transfer in the Electron Donor,Acceptor Complex BH3NH3CHEMINFORM, Issue 23 2004Yirong Mo Abstract For Abstract see ChemInform Abstract in Full Text. [source] Systematic Investigation of Photoinduced Electron Transfer Controlled by Internal Charge Transfer and Its Consequences for Selective PdCl2 CoordinationCHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2010Thomas Schwarze Abstract Fluoroionophores of fluorophore,spacer,receptor format were prepared for detection of PdCl2 by fluorescence enhancement. The fluorescent probes 1,13 consist of a fluorophore group, an alkyl spacer and a dithiomaleonitrile PdCl2 receptor. First, varying the length of the alkylene spacer (compounds 1,3) revealed a dominant through-space pathway for oxidative photoinduced electron transfer (PET) in CH2 -bridged dithiomaleonitrile fluoroionophores. Second, fluorescent probes 4,9 containing two anthracene or pyrene fragments connected through CH2 bridges to the dithiomaleonitrile unit were synthesized. Modulation of the oxidation potential (EOx) through electron-withdrawing or -donating groups on the anthracene moiety regulates the thermodynamic driving force for oxidative PET (,GPET) in bis(anthrylmethylthio)maleonitriles and therefore the fluorescence quantum yields (,f), too. The new concept was confirmed and transferred to pyrenyl ligands, and fluorescence enhancements (FE) greater than 3.2 in the presence of PdCl2 were achieved by 7 and 8 (FE=5.4 and 5.2). Finally, for comparison, monofluorophore ligands 10,13 were synthesized. [source] An Experimental and Computational Study on Intramolecular Charge Transfer: A Tetrathiafulvalene-Fused Dipyridophenazine MoleculeCHEMISTRY - A EUROPEAN JOURNAL, Issue 13 2007Chunyang Jia Prof. Abstract To study the electronic interactions in donor,acceptor (D,A) ensembles, D and A fragments are coupled in a single molecule. Specifically, a tetrathiafulvalene (TTF)-fused dipyrido[3,2- a:2,,3,- c]phenazine (dppz) compound having inherent redox centers has been synthesized and structurally characterized. Its electronic absorption, fluorescence emission, photoinduced intramolecular charge transfer, and electrochemical behavior have been investigated. The observed electronic properties are explained on the basis of density functional theory. [source] Modulating Charge Transfer through Cyclic D,L -,-Peptide Self-AssemblyCHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2005W. Seth Horne Abstract We describe a concise, solid support-based synthetic method for the preparation of cyclic d,l -,-peptides bearing 1,4,5,8-naphthalenetetracarboxylic acid diimide (NDI) side chains. Studies of the structural and photoluminescence properties of these molecules in solution show that the hydrogen bond-directed self-assembly of the cyclic d,l -,-peptide backbone promotes intermolecular NDI excimer formation. The efficiency of NDI charge transfer in the resulting supramolecular assemblies is shown to depend on the length of the linker between the NDI and the peptide backbone, the distal NDI substituent, and the number of NDIs incorporated in a given structure. The design rationale and synthetic strategies described here should provide a basic blueprint for a series of self-assembling cyclic d,l -,-peptide nanotubes with interesting optical and electronic properties. [source] Intramolecular Charge Transfer in Pyrromethene Laser Dyes: Photophysical Behaviour of PM650CHEMPHYSCHEM, Issue 11 2004F. López Arbeloa Prof. Dr. Abstract Absorption and fluorescence (steady-state and time-correlated) techniques are used to study the photophysical characteristics of the pyrromethene 650 (PM650) dye. The presence of the cyano group at the 8 position considerably shifts the absorption and fluorescence bands to lower energies with respect to other related pyrromethene dyes; this is attributed to the strong electron-acceptor character of the cyano group, as is theoretically confirmed by quantum mechanical methods. The fluorescence properties of PM650 are intensively solvent-dependent. The fluorescence band is shifted to lower energies in polar/protic solutions, and the evolution of the corresponding wavelength with the solvent is analysed by a multicomponent linear regression. The fluorescence quantum yield and the lifetime strongly decrease in polar/protic solvents, which can be ascribed to an extra nonradiative deactivation, via an intramolecular charge-transfer state (ICT state), favoured in polar media. [source] Structural Study of Novel Graphite,Lithium,Calcium Intercalation CompoundsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2004Sébastien Pruvost Abstract Three new layered compounds were synthesised by immersing a pyrographite platelet in a molten Ca,Li alloy creating a new graphite intercalation compound family. The samples were studied by X-ray and neutron diffraction, revealing that the intercalated sheets are polylayered. The study of the 00l reflections allowed us to establish the c -axis stacking of these three phases. The ,-phase exhibits a five-layered intercalated sheet which has something in common with a Li,Ca,Li,Ca,Li slice cut in the CaLi2 structure (ThMn2 Laves phase type). The ,-phase, which is richer in metallic elements and with a greater repeat distance, possesses seven-layered intercalated sheets due to the splitting of the middle lithium plane in three. The third phase is a pseudo-binary compound, containing monolayered sheets and with a formula close to CaC6. Electron microdiffraction allowed us to determine the 2D unit cell for each compound, all of which were commensurate with that of graphite. Charge transfer from the intercalate to the host lattice was evaluated for the three phases from hk0 data, leading to high values. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Surface-Transfer Doping of Organic Semiconductors Using Functionalized Self-Assembled Monolayers,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2007W. Chen Abstract Controlling charge doping in organic semiconductors represents one of the key challenges in organic electronics that needs to be solved in order to optimize charge transport in organic devices. Charge transfer or charge separation at the molecule/substrate interface can be used to dope the semiconductor (substrate) surface or the active molecular layers close to the interface, and this process is referred to as surface-transfer doping. By modifying the Au(111) substrate with self-assembled monolayers (SAMs) of aromatic thiols with strong electron-withdrawing trifluoromethyl (CF3) functional groups, significant electron transfer from the active organic layers (copper(II) phthalocyanine; CuPc) to the underlying CF3 -SAM near the interface is clearly observed by synchrotron photoemission spectroscopy. The electron transfer at the CuPc/CF3 -SAM interface leads to an electron accumulation layer in CF3 -SAM and a depletion layer in CuPc, thereby achieving p-type doping of the CuPc layers close to the interface. In contrast, methyl (CH3)-terminated SAMs do not display significant electron transfer behavior at the CuPc/CH3 -SAM interface, suggesting that these effects can be generalized to other organic-SAM interfaces. Angular-dependent near-edge X-ray absorption fine structure (NEXAFS) measurements reveal that CuPc molecules adopt a standing-up configuration on both SAMs, suggesting that interface charge transfer has a negligible effect on the molecular orientation of CuPc on various SAMs. [source] Davydov's solitons in a homogeneous nucleotide chainINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2010Victor D. Lakhno Abstract Charge transfer in homogeneous nucleotide chains is modeled on the basis of Holstein Hamiltonian. The path length of Davydov solitons in these chains is being studied. It is shown that in a dispersionless case, when the soliton velocity V is small, the path length grows exponentially as V decreases. In this case, the state of a moving soliton is quasisteady. In the presence of dispersion determined by the dependence ,2 = , + V,2, the path length in the region 0 < V < V0 is equal to infinity. In this case, the phonon environment follows the charge motion. In the region V > V0, the soliton motion is accompanied by emission of phonons which leads to a finite path length of a soliton. The latter tends to infinity as V , V0 + 0 and V , ,. The presence of dissipation leads to a finite soliton path length. An equilibrium velocity of soliton in an external electric field is calculated. It is shown that there is a maximum intensity of an electric field at which a steady motion of a soliton is possible. The soliton mobility is calculated for the stable or ohmic brunch. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Charge transfer in single- and double-strand DNAs: Theoretical analysis based on molecular orbital methodINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 15 2006Kenichi Dedachi Abstract Electrochemical DNA chips determine the sequence of DNA bases by detecting the change in charge conductivity through single- or double-strand DNA. Experimentally, double-strand DNAs were found to conduct much greater electric current than single-strand DNAs. To gain insight into the underlying mechanism leading to such a disparity in charge conductivity, the hole/electron conductivities in single- and double-strand DNAs were examined theoretically by molecular dynamics and molecular orbital (MO) calculations. The hole/electron transfer integrals between the neighboring DNA bases were estimated from the frontier MO energy levels. The current-voltage characteristics of single- and double-strand DNAs, derived from the transfer integrals and the site energy of each DNA base, are qualitatively in agreement with experiment. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Electronic Spectra of Ti(IV) in Zeolites: An Ab Initio ApproachCHEMPHYSCHEM, Issue 7 2005Ettore Fois Prof. Dr. Charge transfer in Ti,zeolites: Model titanium,zeolites containing a single Ti(IV) tetrahedral species were built and their electronic excitation spectra were calculated (see picture) via time-dependent density functional theory (TDDFT). A multiple-band profile was obtained in each case, thus highlighting that the features observed in the UV/Vis spectra are not a direct evidence of chemically different Ti(IV) sites. [source] The Influence of Doping Levels and Surface Termination on the Electrochemistry of Polycrystalline DiamondELECTROANALYSIS, Issue 6 2004Matthew Abstract The influence of surface chemistry and boron doping density on the redox chemistry of Fe(CN) at CVD polycrystalline diamond electrodes is considered. It is demonstrated that for this couple both the doping density and the surface chemistry are important in determining the rate of charge transfer at the electrode/electrolyte interface. For hydrogen terminated CVD diamond metallic electrochemical behavior is always observed, even at boron doping densities as low as 7×1018,cm,3. In contrast, the electrochemical behavior of oxygen terminated CVD diamond varies with doping density, a metallic response being observed at high doping density and semiconductor behavior at low doping density. It is shown that the results attained may be explained by a surface state mediated charge transfer mechanism, thus demonstrating the importance of controlling surface chemistry in electroanalytical applications of diamond. [source] Electrocatalytic Properties and Sensor Applications of Fullerenes and Carbon NanotubesELECTROANALYSIS, Issue 9 2003Bailure Abstract The electrochemical behavior of fullerene and fullerene derivatives are reviewed with special reference to their catalytic and sensor applications. Recent work on carbon nanotubes, used as catalyst supports in heterogeneous catalysis and sensor development is also presented. An overview of recent progress in the area of fullerene electrochemistry is included. Several cases of electrocatalytic dehalogenation of alkyl halides, assisted by the electrode charge transfer to fullerenes, are discussed. Research work on the electrocatalysis of biomolecules, such as hemin, cytochrome c, DNA, coenzymes, glucose, ascorbic acid, dopamine, etc. have also been considered. Based on the studies of the interaction of fullerenes, fullerene derivatives, and carbon nanotubes with other molecules and biomolecules in particular, the possibilities for the preparation of electrochemical sensors and their application in electroanalytical chemistry are highlighted. [source] Determination of Ytterbium Traces by Cathodic Stripping VoltammetryELECTROANALYSIS, Issue 1 2003Marina Mlakar Abstract The method of ytterbium(III) trace concentration in the presence of 2-thenoyltrifluoroacetone (TTA) and polyethyleneglycol (PEG) in ammonium chloride is described. The adsorption was performed at the HMDE at ,1.0,V using linear scan voltammetry and square-wave voltammetry. The relationship between properties of the SW response of the mixed ligand complex and parameters of a charge transfer were analyzed using theoretical data of SW redox processes. [source] Structural, Spectroscopic, and Proton-Coupled Electron-transfer Behavior of Pyrazolyl-3,5-bis(benzimidazole)-Bridged Homo- and Heterochiral RuIIRuII, OsIIOsII, and OsIIRuII 2,2,-Bipyridine ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2010Sujoy Baitalik Abstract The homo- and heterobimetallic complexes [(bpy)2MII(H2pzbzim)M,II(bpy)2](ClO4)3·nH2O (1, 3, 5) and their corresponding deprotonated complexes [(bpy)2MII(pzbzim)M,II(bpy)2](ClO4)·nH2O (2, 4, 6) [where MII, M,II = Ru (1, 2) = Os (3, 4); MII = Os and M,II = Ru (3, 5); bpy = 2,2,-bipyridine; H3pzbzim = pyrazole-3,5-bis(benzimidazole)] were synthesized, separated to their heterochiral (a, ,,/,,) and homochiral (b, ,,/,,) diastereoisomers, and characterized by elemental analyses, ESI-MS, and 1H NMR spectroscopy. The X-ray structures of 1a, 3a, and 5a show the involvement of two pyridine rings of two bpy ligands in strong intramolecular nonbonded ,,, interaction. The occurrence of a C,H···, interaction between an aromatic C,H and the ,-cloud of a pyridine ring leads to strong electronic shielding of this proton (1H NMR). In all cases, the two diastereoisomers show practically no differences in their absorption spectra, redox potentials, and pK values. The large shifts in the E1/2 values to less positive potentials and substantial redshifts in the MLCT bands that occur on deprotonation of 1, 3, and 5 are energetically correlated. From the profiles of E1/2(1), (2) vs. pH over the pH range 1,12, the equilibrium constants and standard redox potentials for all the complex species in the metal oxidation states II·II, II·III, and III·III and the bridged ligand in the protonation states H2pzbzim,, Hpzbzim2,, and pzbzim3, have been evaluated. Using these values the bond dissociation free energies for the benzimidazole N,H bonds have been estimated. Spectroelectrochemical studies have been carried out for 1a, 3a, and 5a in the range 400,1100 nm. With stepwise oxidation of the metal centers replacement of MLCT bands by LMCT bands occur gradually with the observation of sharp isosbestic points. In the case of 1a, a band observed at ,max = 910 nm for the RuIIRuIII species has been ascribed to intervalence charge transfer (IVCT) transition. [source] A Dinuclear Double-Stranded Oxido Complex of ReV with a Bis(benzene- o -dithiolato) LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 27 2009Jorge S. Gancheff Abstract The reaction of [ReOCl3(PPh3)2] with 1,2-bis(2,3-dimercaptobenzamido)ethane (H4 - 1) in the presence of Na2CO3 in methanol under anaerobic conditions affords the dinuclear ReV oxido complex [PPh4]2[ReO(1)]2 containing two distorted square-pyramidal {ReVOS4} units bridged by the ligand strands in a double-stranded fashion. The coordinationgeometry around the metal centers is similar to the one observed for [ReO(bdt)2],. The ReS4 planes are arranged in a coplanar fashion and are not twisted around the metal,metal vector, which prevents the complex to adopt a helical structure. Luminescence studies show the presence of emission bands, which are assigned to singlet-singlet transitions exhibiting very fast decays (ca. 10 ns). Theoretical Density Functional (DFT) studies on geometry and electronic properties were performed employing the hybrid B3LYP and PBE1PBE functionals. While the general trends observed in the experimental data are well reproduced in all cases, a good agreement was obtained using PBE1PBE, in particular for the Re,S bonds. Natural Bond Orbitals (NBO) analysis indicates the presence of polarized Re,O and Re,S bonds, both of them polarized toward the non-metal. The calculation show that the molecular orbitals of the ReV are doubly degenerated, the occupied 5d orbital of rhenium lying beneath occupied sulfur-based MOs due to the rigid geometry imposed by the C,C backbone of the bis(benzene- o -dithiolato) ligands. The origin of all absorption bands is ascribed to a ligand-to-metal charge transfer (LMCT), in which occupied sulfur-based orbitals and unoccupied rhenium-centered orbitals are involved.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Uncommon Solvent Effect in Oxidative Addition of MeI to a New Dinuclear Platinum Complex Containing a Platina(II)cyclopentane MoietyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 32 2008S. Jafar Hoseini Abstract The reaction of the known complex cis,cis -[Me2Pta(,-dppm)(,-SMe2)Ptb,CH2(CH2)2CcH2(Ptb,Cc)] [dppm = bis(diphenylphosphanyl)methane] with phthalazine (NN) proceeded by replacement of the labile bridging SMe2 ligand with the bidentate N-donor ligand NN to give cis,cis -[Me2Pta(,-dppm)(,-NN)Ptb,CH2(CH2)2CcH2(Ptb,Cc)] (1) as a pale red solid in good yield. The complex was fully characterized by multinuclear (1H, 31P, 195Pt) NMR spectroscopy. The subsequent reaction of complex 1 with excess MeI gave the colorless diplatinum(IV) complex [Me3Pta(,-dppm)(,-I)2Ptb{CH2(CH2)2CcH2(Ptb,Cc)}Me], in which the bridging NN ligand is replaced by bridging iodido ligands. The reddish color of complex 1, which is due to a metal-to-ligand charge transfer (MLCT) band in the visible region, was used to monitor its reaction with MeI in the solvents acetone, CH2Cl2, and benzene. The kinetic data revealed that the reactions in nonpolar benzene or slightly polar CH2Cl2 proceeded in two steps, each following a common SN2 mechanism. In the first step, MeI attacked the platina(II)cyclopentane center rather than the dimethylplatinum(II) center, because the first center is more electron-rich than the second center. In the more polar acetone, the reaction proceeded similarly, with the exception that each step was accompanied by a solvolytic reaction, which was suggested to be responsible for the unusually slower reaction rate in acetone than in benzene or CH2Cl2. Consistently, the reaction rate in the highly polar solvent CH3CN was too slow for any meaningful measurement.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Multicomponent Supramolecular Devices: Synthesis, Optical, and Electronic Properties of Bridged Bis-dirhodium and -diruthenium Complexes,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2006Anne Petitjean Abstract Four ruthenium- and rhodium-based metal,metal-bonded multicomponent systems have been synthesized, and their absorption, redox, spectroelectrochemical and structural properties have been studied. The absorption spectra of the four bis-dimetallic compounds M2LM2, where L is a bridging ligand and M is rhodium or ruthenium, exhibit very strong bands in the UV, visible and, for the diruthenium species, near-IR region. The low-energy absorption bands are assigned to charge-transfer transitions involving a metal,metal bonding orbital as the donor and an orbital centered on the bis-tetradentate aromatic ligands as the acceptor (metal,metal to ligand charge transfer, M2LCT). Each compound exhibits reversible bridging-ligand-centered reductions at mild potentials and several reversible oxidation processes. The oxidation signals of the two equivalent dimetallic centers of each bis-dimetallic compound are split, with the splitting , a measure of the electronic coupling , depending on both the metal and bridging ligand. The mixed-valence species of the dirhodium species was investigated, and the electronic coupling matrix element calculated from the experimental intervalence band parameters for one of them (86 cm,1) indicates a significant inter-component electronic interaction which compares well with good electron conducting anionic bridges such as cyanides. Although none of these compounds is luminescent, the M2LCT excited state of one of the bis-dirhodium complexes is relatively long-lived (about 6 ,s) in degassed acetonitrile at room temperature. The results presented here are promising for the development of linear poly-dimetallic complexes built on longer naphthyridine-based strands, with significant long-range electronic coupling and molecular-wire-like behavior. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Dimeric 2,2,-Bipyridylruthenium(II) Complexes Containing 2,2,-Bis(1,2,4-triazin-3-yl)-4,4,-bipyridine-Like Bridging Ligands: Syntheses, Characterization and DNA BindingEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2004Cai-Wu Jiang Abstract Three new bridging ligands 2,2,-bis(1,2,4-triazin-3-yl)-4,4,-bipyridine (btb), 2,2,-bis(1,2,4-triazino[5,6-f]acenaphthylen-3-yl)-4,4,-bipyridine (btapb), 2,2,-bis(5,6-diphenyl-1,2,4-triazin-3-yl)-4,4,-bipyridine (bdptb) and their dimeric 2,2,-bipyridylruthenium(II) complexes [Ru(bpy)2(btb)Ru(bpy)2]4+ (1), [Ru(bpy)2(btapb)Ru(bpy)2]4+ (2), [Ru(bpy)2(bdptb)Ru(bpy)2]4+ (3) have been synthesized and characterized by elemental analysis, fast atom bombardment (FAB) mass spectrometry or electrospray mass spectrometry (ES-MS), 1H NMR and UV/Visible spectroscopy. The binding behavior of these dimeric complexes with calf thymus DNA (CT-DNA) was investigated by electronic absorption spectroscopy, viscosity measurements, and equilibrium dialysis experiments. The hypochromism of the metal-ligand charge transfer (MLCT) band in the electronic absorption spectra of the dinuclear complexes 1, 2, and 3 is 8.7%, 19% and 33%, respectively, with bathochromic shifts of 5, 5 and 14 nm, respectively. The binding constants are 7.5×104M,1, 4.8×105M,1 and 7.6×105M,1, respectively. Increasing the size of the plane of the bridging ligand increases the hydrophobicity of their complexes, leading to stronger binding by the complexes to calf thymus DNA. The effect of increasing concentrations of these novel dimeric ruthenium(II) complexes on the relative viscosities of CT-DNA is less notable than that of well-known intercalators such as [Ru(bpy)2(dppz)]2+. The equilibrium experiments showed that ,,,3 binding is stronger than ,,,3 binding to CT-DNA. This is the first example of a dinuclear complex binding enantioselectively to CT-DNA measured by equilibrium dialysis. The experiments suggest that the three complexes may be DNA groove binders. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Solid-State Adducts between C60 and DecamethylferroceneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2003Aldo Arrais Abstract Co-deposition from concentrated solutions of C60 and Fe[C5(CH3)5]2 affords two solid products in different yields. The major product 1, in the form of regular shaped crystals, has been investigated by X-ray diffraction, 13C CPMAS NMR and vibrational spectroscopy, which showed it to be a co-crystalline adduct of C60 and Fe[C5(CH3)5]2 with no significant electron charge transfer between the two building blocks. The minor product 2, in the form of an amorphous powder, has been investigated by vibrational techniques. Both IR and Raman spectra are consistent with a solid structure in which electron transfer between the two units appears to be possible. ((© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] | ||||||||||||||||||||||||||||||||||||||||||||||