Gold(II) Porphyrins in Photoinduced Electron Transfer Reactions

In the context of solar-to-chemical energy conversion, inspired by natural photosynthesis, the synthesis, electrochemical properties and photoinduced electron-transfer processes of three novel zinc(II)-gold(III) bis(porphyrin) dyads [Zn^II(P)–Au^III(P)]⁺ are presented (P: tetraaryl porphyrin). Time-resolved spectroscopic studies indicated ultrafast dynamics (k >10¹⁰ s⁻¹) after visible-light excitation, which finally yielded a charge-shifted state [Zn^II(P ^{⋅ +})–Au^II(P)]⁺ featuring a gold(II) center. The lifetime of this excited state is quite long due to a comparably slow charge recombination (k ≈3×10⁸ s⁻¹). The [Zn^II(P ^{⋅ +})–Au^II(P)]⁺ charge-shifted state is reductively quenched by amines in bimolecular reactions, yielding the neutral zinc(II)–gold(II) bis(porphyrin) Zn^II(P)–Au^II(P). The electronic nature of this key gold(II) intermediate, prepared by chemical or photochemical reduction, is elucidated by UV/Vis, X-band EPR, gold L₃-edge X-ray absorption near edge structure (XANES) and paramagnetic ¹H NMR spectroscopy as well as by quantum chemical calculations. Finally, the gold(II) site in Zn^II(P)–Au^II(P) is thermodynamically and kinetically competent to reduce an aryl azide to the corresponding aryl amine, paving the way to catalytic applications of gold(III) porphyrins in photoredox catalysis involving the gold(III/II) redox couple.     

Organic-Inorganic Sol-Gel Hybrids with Ionic Properties

 A hybrid silicon precursor (ICS-PPG) obtained by reaction of 3-isocyanatopropyltriethoxy silane with poly-(propyleneglycol)-bis-(2-aminopropyl ether) was recognized as a potential host for various salts and molecular species. It has been used for electrochromic, gasochromic, photovoltaic, and fuel cell applications. This focuses on proton conducting gels (PWA/ICS-PPG, SiWA/ICS-PPG, and W-PTA/ICS-PPG) obtained after the incorporation of polyoxometalates in the ICS-PPG host. IR spectroscopic measurements are used to reveal the entrapment, the aggregation, and the interactions of W-PTA, PWA, or SiWA with the sol-gel derived network. The proton conductivity of the composites, measured using impedance spectroscopy, increases with increasing concentration of the polyoxometalates from 10⁻⁶ to 10⁻³ S/cm.     

Untersuchung von Fetten und ?len

Ohne Zusammenfassung     

Optische Bestimmung der elektrolytischen Dissoziation in sehr verdünnter äthylalkoholischer Lösung

Ohne Zusammenfassung     

Correlation between crystal symmetry and the splitting of d orbital in the thiocyanate nickel(II) complexes

New [Ni(SCN)₂(L)_4/2] complexes, where L = py (1), γ-pic (2), pyCH₂OH (3), py(CH₂)₃OH (4) were synthesized in simple reactions of NiCl₂·6H₂O with ammonia thiocyanate and pyridine type ligands in methanol solutions. Blue crystals of [Ni(SCN)₂(py)₄] (1), [Ni(SCN)₂(pyCH₂OH)₂] (3) and [Ni(SCN)₂(py(CH₂)₃OH)₂] (4) crystallize in the monoclinic system, blue crystal of [Ni(SCN)₂(γ-pic)₄] (2) – in the tetragonal one, and red crystal of [Ni(SCN)₂(PPh₃)₂] (5) – in the triclinic one. The ligands of complexes (1) and (3) were indicated as rather strong π-acceptors while that of complex (4) one has some π-donor properties. When the aliphatic chain (CH₂) elongates in the sequence: (1), (3) and (4), an increase in the orbital contribution to the magnetic moment and a decrease in the 10Dq value of the d orbital splitting are related to the change of the point group symmetry from D_2h, via D_2v to C_2h.     

Stop location design in public transportation networks: covering and accessibility objectives

We consider the location of new stops along the edges of an existing public transportation network. Examples of StopLoc include the location of bus stops along some given bus routes or of railway stations along the tracks in a railway system. In order to evaluate the decision assume that potential customers in given demand facilities are known. Two objectives are proposed. In the first one, we minimize the number of stations such that any of the demand facilities can reach a closest station within a given distance of r. In the second objective, we fix the number of new stations and minimize the sum of the distances between demand facilities and stations. The resulting two problems CovStopLoc and AccessStopLoc are solved by a reduction to a classical set covering and a restricted location problem, respectively. We implement the general ideas in two different environments, the plane, where demand facilities are represented by coordinates, and in networks, where they are nodes of a graph.