EPR-Untersuchungen an Nitrosyl-Eisen-Chelaten des Typs [FeNO(S,S)(P,P)]

EPR Investigations on Nitrosyl Iron Chelates of the Type [FeNO(S, S)(P, P)] The EPR powder spectra of [FeNO(mnt)(diphos)] and {FeNO(mnt)[P(C₆H₅)₃]₂} (mnt = maleonitriledithiolate, diphos = tetraphenylethylenediphosphine), diamagnetically diluted in the corresponding cobalt chelates, are reported. The nitrosyl iron chelate {FeNO(mnt)[P(C₆H₅)₃]₂} could, However, be only isolated in the host chelate. According to the EPR parameters obtained for [FeNO(mnt)(diphos)] the MO of the unpaired electron consists of the metal d_z2 and the corresponding ligand orbitals. The g tensor components and the ligand hyperfine structure coupling constants found for {FeNO(mnt)[P(C₆H₅)₃]₂} are more in agreement with an MO for the unpaired electron consisting of the metal d_yz and the corresponding ligand orbitals. Large structural deviations are responsible for this difference.     

3He NMR: from free gas to its encapsulation in fullerene

The ³He nuclear magnetic shieldings were calculated for single helium atom, its dimer, simple models of fullerene cages (He@C_n), and single wall carbon nanotubes. The performances of several levels of theory (HF, MP2, DFT‐VSXC, CCSD, CCSD(T), and CCSDT) were tested. Two sets of polarization‐consistent basis sets were used (pcS‐n and aug‐pcS‐n), and an estimate of ³He nuclear magnetic shieldings in the complete basis set limit using a two‐parameter fit was established. Theoretical ³He results reproduced accurately previously reported theoretical values for helium gas, dimer, and helium probe inside several fullerene cages. Excellent agreement with experimental values was achieved. ³He nuclear magnetic shieldings of single helium atom approaching various points of benzene ring were tested, and an impact of ³He confinement within fullerene cages of different size on the ³He chemical shift was determined. Copyright © 2013 John Wiley & Sons, Ltd.     

Potential 1,1′-binaphthyl NLO-phores with extended conjugation between positions 2 and 6, and 2′ and 6′

A synthetic approach is reported which allows independent introduction of alkynyl groups to positions 2,2′ and then to 6,6′ of binaphthyls. The approach is based on the high selectivity of the Stephens-Castro alkynylation of 6,6′-dibromo-2,2′-diiodo-1,1′-binaphthyl. The tetraalkynylated derivatives exhibit extended conjugation between groups at positions 2 and 6, and 2′ and 6′, achieved by overcoming steric hindrance at positions 2 and 2′ by using alkynyl spacers.     

Calorimetric studies of adsorption of aromatic hydrocarbons on silicalite

Conclusions Complex relationships between the differential adsorption heats and the degree of filling are observed when benzene and toluene are adsorbed on silicalite. A possible reason for this phenomenon is either a redistribution or a reorientation of the adsorbed molecules when the degree of filling exceeds 0.5.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2820–2823, December, 1982.The authors express their gratitude to Dr. Fahlke for synthesizing and supplying the silicalite sample.     

Zum Mechanismus der Reaktion von Organonickel-verbindungen des Typs (dipy)NiR2 mit Aldehyden und Nitrosoverbindungen. Eine ESR-Untersuchung

Contributions to the Mechanism of the Reaction of Organonickel Compounds of the Type (bipy)NiR₂ (R = ? C₂H₅, ? CH₂? Ph) with Aldehydes and Nitroso Compounds. An ESR Study ESR investigations of the reaction of (bipy)Ni(C₂H₅)₂ and (bipy)Ni(CH₂Ph)₂ with nitrosodurene show a different behaviour during the start process. In the former case first of all a paramagnetic unstable complex compound was detected containing R? NO as a ligand. After that R? NO is shown to cause a radicalic elimination of the ethyl ligands. For (bipy)Ni(CH₂Ph)₂ the formation of a paramagnetic complex intermediate is not observed because of sterical reasons; the radicalic elimination process take place immediately. In presence of propionic aldehyde or benzaldehyde nitrosodurene as a hetero-π-system completes with the aldehydes giving rise to radical reactions. In the absence of nitrosodurene propionaldehyde will be dimerized catalytically by the (bipy)NiR₂ complexes. The mechanism of these reactions will be discussed.     

Untersuchungen zur Reaktivität von Organo-Nickel-Verbindungen – „Spin-Trapping”︁ als Indikatormethode für die relative Reaktivität von Nickel-Kohlenstoff-Bindungen

Investigations to the Reactivity of Organonickel Compounds – “Spin Trapping” as an Indicator Method for the Relative Reactivity of Nickel-Carbon Bonds The spin trap nitrosodurene reacts with σ-alkyl, σ-aryl, π-allyl, σ-allyl, and π-cyclopentadienyl compounds of nickel(II) to form nitrosoduryl radicals which can be detected by ESR spectroscopy. Nickelolefine and nickel heteroolefine complexes do not react by formation of radicals. The spin trapping method can be generally used as an indicator for determination of structure elements in organonickel compounds and for determination of the relative reactivity of σ- and π-bonded groups.     

Spectral Signatures of Oxidation States in a Manganese-Oxo Cubane Water Oxidation Catalyst

We report IR and UV/Vis spectroscopic signatures that allow discriminating between the oxidation states of the manganese-based water oxidation catalyst [(Mn₄O₄)(V₄O₁₃)(OAc)₃]³⁻. Simulated IR spectra show that V=O stretching vibrations in the 900–1000 cm⁻¹ region shift consistently by about 20 cm⁻¹ per oxidation equivalent. Multiple bands in the 1450–1550 cm⁻¹ region also change systematically upon oxidation/reduction. The computed UV/Vis spectra predict that the spectral range above 350 nm is characteristic of the managanese-oxo cubane oxidation state, whereas transitions at higher energy are due to the vanadate ligand. The presence of absorption signals above 680 nm is indicative of the presence of Mn^III atoms. Spectroelectrochemical measurements of the oxidation from [Mn Mn ] to [Mn ] showed that the change in oxidation state can indeed be tracked by both IR and UV/Vis spectroscopy.