Search results for "Spectroscopy."

Aminosäureester als chirale Hilfsgruppen in Lewis-Säure-katalysierten Umsetzungen elektronenreicher Siloxydiene mit Iminen

1990

Four new eremophilendiolides from Ligularia atroviolacea

2007

From Ligularia atroviolacea, four new eremophilendiolides, 8 beta-hydroxy-eremophil-3,7 (11)-dien-12,8 alpha(14,6 alpha)-diolide (1), 8 beta-methoxy-eremophil-3,7(11)-dien-12,8 alpha(14,6 alpha)-diolide (2), 8 alpha-hydroxy-eremophil-3,7(11)-dien-12,8 beta(14,6 alpha)-diolide (3) and eremophil-3,7(11),8-trien-12,8 (14,6 alpha)-diolide (4), as well as a known diolide (5) were isolated. Their structures were elucidated on the basis of 1D and 2D NMR as well as ESI-MS spectral data. (c) 2006 Yu Zhao. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Controlling Spin-Correlated Radical Pairs with Donor-Acceptor Dyads: A New Concept to Generate Reduced Metal Complexes for More Efficient Photocataly…

2021

Abstract One‐electron reduced metal complexes derived from photoactive ruthenium or iridium complexes are important intermediates for substrate activation steps in photoredox catalysis and for the photocatalytic generation of solar fuels. However, owing to the heavy atom effect, direct photochemical pathways to these key intermediates suffer from intrinsic efficiency problems resulting from rapid geminate recombination of radical pairs within the so‐called solvent cage. In this study, we prepared and investigated molecular dyads capable of producing reduced metal complexes via an indirect pathway relying on a sequence of energy and electron transfer processes between a Ru complex and a cova…

Non-covalent graphene nanobuds from mono- and tripodal binding motifs.

2017

Graphene nanobuds were prepared via the non-covalent anchoring of C60-based molecules endowed with one or three pyrene units, respectively. TGA, FTIR, UV-Vis and TEM investigations confirmed the formation of nanohybrids. For the two molecular derivatives, striking differences were determined in their interaction with graphene or carbon surfaces by Raman, cyclic voltammetry and molecular mechanics calculations, revealing the important role of pyrene adsorption in modulating the electronic properties of the nanohybrids.

Temperature-Induced Structural Transitions in the Gallium-Based MIL-53 Metal–Organic Framework

2013

We report a structural and thermodynamic investigation of the phase behavior of Ga(OH,F)-MIL-53, a gallium-based metal–organic framework (MOF) having the MIL-53 topology containing 0.7 wt % fluorine bonded to the metal. Despite some small structural differences, especially for the hydrated form, the overall physical chemistry behavior of Ga(OH,F)-MIL-53 is very similar to standard fluorine free Ga-MIL-53 material. A combination of in situ X-ray diffraction, in situ Fourier transform infrared spectroscopy, differential scanning calorimetry, and heat capacity measurements allowed us to establish that Ga(OH,F)-MIL-53 under vacuum (i.e., the empty material) exhibits two stable phases: a nonporo…

Synthesis, crystallographic and electrochemical study of ethynyl[2.2]paracyclophane derived cobalt metallatetrahedranes

2012

Abstract A series of alkynyl cobalt complexes [Co2(μ-η2-HCC–PCP)(CO)6−nLn] [n = 0 (2); n = 2, L2 = dppa (3), dppm (4), dcpm (6), 2 P(OPh)3 (7)] and [Co2(CO)4L2]2(μ-η2:μ-η2-HCC–PCP–CCH)] (L2 = dppm (8), dcpm (9); (PCP = [2.2]paracyclophane) has been prepared and characterized. The molecular structures of 3 and 4, as well as that of [Co2(CO)4(μ-CO)2(μ2-dcpm)] (5), have been determined by X-ray diffraction. Electrochemical studies (Cyclic Voltammetry, Rotating Disk Electrode) and luminescence spectroscopy have been used to evaluate the extent of the electronic communication through the PCP motif using the “Co2C2” centres as a probe. No electronic coupling between the Co2(CO)n centres via the b…

Magneto-structural correlations and DFT calculations in two rare tetranuclear copper(II)-clusters with doubly phenoxo and end-on azido bridges: Synth…

2010

International audience; By slightly changing the synthetic conditions, we have prepared two closely related linear tetranuclear CuII complexes with the symmetrical ONNO donor tetradentate Schiff-base ligand [H2L = (OH)C6H4(CH3)Cdouble bond; length as m-dashN(CH2)3Ndouble bond; length as m-dashC(CH3)C6H4(OH)] and with azide ions. These two distinctly coloured crystalline products were characterized by elemental analysis, IR and UV–Vis spectroscopy, CV, EPR spectra and variable temperature magnetic measurements. Single crystal X-ray diffraction studies of the green [Cu4(μ-L)2(μ1,1-N3)2(N3)2] (1) and the red [Cu4(μ-L)2(μ1,1-N3)2(N3)2(H2O)2] (2) crystals show that the coordination environment o…

Platinum in indoor settled dust matter (homes and cars)

2015

Abstract This paper presents a method for Pt analysis in indoor (homes and cars) settled dust, used as passive samplers, and the results relative to samples collected in the Sicilian area are used to evaluate the magnitude and distribution of concentrations inside common environments and the possible origins of the considered contaminant. The concentrations of platinum in settled indoor dust were measured by differential pulsed voltammetry (DPV). Concentrations of Pt in homes are in the range from 30 to 1460 μg kg − 1 d.w. while, in the vehicles from 30 to 1750 μg kg − 1 d.w. Considering the geoaccumulation index (I geo ), 42% of the settled dust sampled in homes could be classified as extr…

Growth, characterization, and high-pressure optical studies of CuWO4

2008

Copper tungstate (CuWO4) crystals grown by the top-seeded solution growth method were characterized by X-ray diffraction, Raman scattering, and optical measurements. CuWO4 has a triclinic structure (P 1¯) with a = 4.709 A, b = 5.845 A, c = 4.884 A, α = 88.3°, β = 92.5°, and γ = 97.2°. It consists of corner-linked CuO6 and WO6 octahedra, the former having a pseudo-tetragonally elongated geometry caused by the Cu2+ Jahn–Teller effect. Fifteen out of the eighteen Raman modes of CuWO4 are reported, discussed, and compared with those of other tungstates. We also determined the indirect band-gap energy of CuWO4 (2.3 eV) and its negative pressure coefficient up to 25 GPa. The pressure evolution of…

Application of pressurized fluid extraction to determine cadmium and zinc in plants

2006

Abstract A procedure for the determination of Cd and Zn in plants is proposed. The metals are extracted by pressurized fluid extraction (PFE). Operational conditions are: pressure 1500 psi, temperature 75 °C, static time 5 min, flush volume 35%, purge time 60 s, cycles 1 and 1,2-diaminocyclohexane- N , N , N ′, N ′-tetraacetic acid (CDTA) 0.01 M at pH 4.5 as extracting solution. Determination of Zn is carried out by flame atomic absorption spectroscopy and depending on the concentration level, Cd content is determined by flame or electrothermal atomic absorption spectroscopy. Certified samples of Virginia tobacco leaves, tea leaves, spinach leaves, poplar leaves, a commercial spinach sample…