Ultrafast excited-state excitation dynamics in a quasi-two-dimensional light-harvesting antenna based on ruthenium(II) and palladium(II) chromophores

A detailed study on the excited-state-excitation migration taking place within the tetranuclear complex [{(tbbpy)(2)Ru(tmbi)}(2){Pd(allyl)}(2)](PF(6))(2) (tbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine and tmbi = 5,6,5',6'-tetramethyl-2,2'-bibenzimidazolate) is presented. The charge transfer is initiated by the photoexcitation into the lowest metal-to-ligand charge-transfer (MLCT) band of one of the peripheral ruthenium(II) chromophores and terminates on the central structurally complex Pd(2) (II)(allyl)(2) subunit. Thus, the system under investigation can be thought of as a functional model for the photosynthesis reaction center in plants. The kinetic steps involved in the overall process are inferred from femtosecond time-resolved transient-grating kinetics recorded at spectral positions within the regions of ground-state bleach and transient absorption. The kinetics features a complex non-exponential time behavior and can be fitted to a bi-exponential rise (tau(1)> or =200 fs, tau(2) approximately 1.5 ps) and a mono- or bi-exponential decay, depending on the experimental situation. The data leads to the formulation of a model for the intramolecular excitation-hopping ascribing intersystem crossing and subsequent cooling as the two fastest observed processes. Following these initial steps, charge transfer from the ruthenium to the central complex Pd(2)(allyl)(2) moiety is observed with a characteristic time constant of 50 ps. A 220-ps component that is observed in the ground-state recovery only is attributed to excitation equilibration between the two identical Pd(allyl) chromophores.     

Zinn(IV)-Komplexe mit dreizähnigen diaciden Liganden — 119Sn-NMR und 119mSn-Mössbauer-spektroskopische Untersuchungen

Tin(IV) Complexes with Tridentate Diacidic Ligands — ¹¹⁹Sn NMR and ^119mSn Mössbauer Studies The tin(IV) chelates of tridentate diacidic azomethines of acetylacetone resp. salicylaldehyde with benzoylhydrazine, thiobenzoylhydrazine, 2-hydroxyaniline and 2-mercaptoaniline as well as with the ligands 2-(2′-hydroxy-4-methylphenyl)-6-(2″-hydroxyphenyl)pyridine, 2-(2′-hydroxyphenyl)-8-quinolinol and 2.6-diphenacylpyridine were synthesized. The compounds were characterized by IR-, UV/VIS-, MS-, ¹¹⁹Sn NMR and ^119mSn Mössbauer spectroscopy. They exist as a mixture of geometrical isomers.     

Chelate von β-dicarbonylverbindungen und ihren derivaten—teil XLIV. Die extraktion von silber,gold, palladium und platin mit thiodibenzoylmethan1

The extraction of silver(I), gold(III), palladium(II) and platinum(IV) with thiodibenzoylmethane is reported, and methods for the extraction—photometric determination of silver and palladium in trace concentrations are described. Addition of EDTA allows a satisfactory selectivity to be achieved. The influence of foreign metals and complexing agents is discussed.     

Vanadium-Komplexe mit dreizähnigen diaciden Liganden. Die Kristallstrukturen von Bis[acetylacetonthiobenzoylhydrazonato(2-)]vanadium(IV), Methoxo-oxo-[salicylaldehydthiobenzoylhydrazonato(2-)]vanadium(V) und Methoxo-oxo-[salicylaldehydbenzoylhydrazonato(2-)]methanolvanadium(V)

Vanadium Complexes with Tridentate Diacidic Ligands. The Crystal Structures of Bis[acetylacetonato-thiobenzoylhydrazonato(2-)]vanadium(IV), Methoxo-oxo-[salicylaldehyd-thiobenzoylhydrazonato(2-)]vanadium(V), and Methoxo-oxo-[salicylaldehydbenzoylhydrazonato(2-)]methanol Vanadium(V) By template reactions of bis(acetylacetonato)oxovanadium(IV) and bis(salicylaldehydato)oxo-vanadium(IV), respectively, with benzoylhydrazine, thiobenzoylhydrazine, and 2-aminophenol the vanadium(IV) complexes V(LLL)₂ of tridentate azomethine ligands LLL were synthesized. The complexes were characterized by EPR spectroscopy and by absorption spectroscopy. From the complex V(LLL)₂ ( 1 ), in which LLL is acetyl-aceton-thiobenzoydrazonate(2-), the crystal structure analysis was solved. The vanadium atom in 1 is coordinated trigonal-prismatically by two N, 0 and S atoms. Furthermore, the 0x0 vanadium(V) complexes[VO(LLL)(OCH,)] (6) with LLL = salicylaldehyd-thio-benzoylhydrazonato(2-) and [VO(LLL)(OCH₃)· -CH₃OH] (7) with LLL = salicylaldehydbenzoylhydrazonato(2-) were identified by X-ray diffraction and by IR spectroscopy in the reaction products. Crystallographic data for 1, 6 , and 7 see ?Inhaltsübersicht”?.     

Pulse magnetoelectrolysis

We present a novel technique consisting in the combination of pulse plating and magnetoelectrolysis. This technique is applied to copper electrolysis between two vertical copper-electrodes. The modulation of the current inside an inhomogeneous magnetic field generates a modulated Lorentz force driving an oscillating convection studied using particle image velocimetry. The resulting changes in the concentration boundary layers are analysed by means of a Mach-Zehnder interferometer.     

Desorption of hydrogen from an electrode surface under influence of an external magnetic field – In-situ microscopic observations

The effect of a magnetic field in the perpendicular-to-electrode configuration on the hydrogen evolution reaction (HER) was investigated during the deposition of Co. An enhanced desorption of hydrogen in the form of numerous small bubbles was found by combining potentiostatic investigations, coupled with an electrochemical quartz crystal microbalance (EQCM), and simultaneous microscopic observations of the electrode surface. The results are consistent with the recently proposed qualitative model [J.A. Koza, M. Uhlemann, A. Gebert, L. Schultz, Electrochem. Commun. 10 (2008) 1330].     

Chelate von β-diketonderivaten1: Teil X. Zweiphasenverteilung von thiodibenzoylmethan und seinen kupfer-, nickel- und kobaltchelaten

The solubility of thiodibenzoylmethane, as well as its distribution coeffieients between water and organic solvents, and the enol dissociation constant were studied. The extraction of copper, nickel, and cobalt by solutions of thiodibenzoylmethane in n-heptane or tetrachloromethane is described; these extractions are practicable at lower pH values than for dibenzoylmethane, and only a very small excess of reagent over the stoichiometric quantity is needed.     

Structured electrodeposition in magnetic gradient fields

Electrodeposition in superimposed magnetic gradient fields is a new and promising method of structuring metal deposits while avoiding masking techniques. The magnetic properties of the ions involved, their concentrations, the electrochemical deposition parameters, and the amplitude of the applied magnetic gradient field determine the structure generated. This structure can be thicker in regions of high magnetic field gradients. It can also be free-standing or inversely structured. The complex mechanism of structured electrodeposition of metallic layers in superimposed magnetic gradient fields was studied by different experimental methods, by analytical methods and by numerical simulation and will be discussed comprehensively.     

Struktur und ausgewählte Reaktionen von ReCl4(PPh3)2

ReCl₄(PPh₃)₂ – Reactions and Structure The compounds ReCl₄(PPh₃)₂ and Re₂OCl₃(C₂H₅COO)₂(PPh₃)₂ resulting from the reaction of ReOCl₃(PPh₃)₂ with PPh₃ in boiling propionic acid and HCl atmosphere were characterized by their VIS-spectra and structural data. Ligand exchange reactions with acetylacetone gave ReCl₂(acac)₂ as well as ReCl₂(acac)(PPh₃)₂. Crystallographic data see “Inhaltsübersicht”.