Search results for "absorption spectroscopy"

Aminoferrocene and Ferrocene Amino Acid as Electron Donors in Modular Porphyrin–Ferrocene and Porphyrin–Ferrocene–Porphyrin Conjugates

2014

New amide-linked porphyrin–ferrocene conjugates [M(PAr)–Fc] were prepared from aminoferrocene and a carboxy-substituted meso-tetraaryl-porphyrin [M = 2H, Zn; Ar = mesityl (Mes), C6F5: 3a, 3e, Zn-3a, Zn-3e]. A further porphyrin building block was attached to the second cyclopentadienyl ring of the ferrocene moiety to give the metallopeptides M(PMes)–Fc–M(PAr) (M = 2H, Zn; Ar = C6H5, 4-C6H4F: 6b, 6c, Zn-6b, Zn-6c). The effects of the Ar substituents, the porphyrin central atom M and the presence of the second porphyrin at the ferrocene hinge on the excited-state dynamics was studied by optical absorption spectroscopy, electrochemistry, steady-state emission, time-resolved fluorescence measure…

A New Co-Ni-Heterometallic Butterfly Complex Obtained via a Novel Synthesis Approach

2011

Abstract. The heterometallic complex [Co2Ni2(OH)2(O2CtBu)6(HOEt)6]·2EtOH (1) with a so called butterfly structural motif was prepared by reaction of the homometallic precursor complexes [Co2(H2O)(O2CtBu)4(HO2CtBu)4] and [Ni2(H2O)(O2CtBu)4(HO2CtBu)4] in an one to one ratio under elevate temperature. Complex 1 was characterized by single-crystal X-ray diffraction, atomic absorption spectroscopy, elemental analyses, IR spectroscopy, and mass spectrometry. The magnetic data show an overall antiferromagnetic behavior, which can be explained with three different coupling constants, resulting in a paramagnetic ground state.

Dopant-Host oxide interactions and proton mobility in Gd:BaCeO3

2009

The local structure of Gd:BaCeO3 at different dopant concentrations (2-20%) was studied by X-ray absorption spectroscopy. The EXAFS analysis shows that the environment of the regular Ba2+ and Ce4+ cations is to a limited extent affected by doping. The local structure of gadolinium shows an expansion of the first coordination shell of oxygens, consistent with the ionic radius of Gd3+, but a contraction of the next neighboring shells of cations. In particular, the Ba2+ second neighbors get closer to the dopant, which can be originated by the effective negative charge sharply localized on the dopant. Comparison between EXAFS data of dry and hydrated compounds confirms this interpretation, show…

Neutral solar photo-Fenton degradation of 4-nitrophenol on iron-enriched hybrid montmorillonite-alginate beads (Fe-MABs)

2014

Hybrid montmorillonite-alginate beads (MABs) were prepared by the ion-gelation method from alginate and montmorillonite clay suspension dropped in a calcium chloride solution. Similarly, iron-enriched beads (Fe-MABs) were prepared using iron-exchanged montmorillonite. All beads were characterized by atomic absorption and Fourier-transform infrared spectroscopy. The efficiency of Fe-MABs as catalysts for the solar photo-Fenton performed at initial pH = 7.0 was evaluated by varying the catalyst amount and hydrogen peroxide concentration, and monitoring the removal of 4-nitrophenol (4-NP) at initial concentration of 10 ppm. A kinetic analysis showed that the removal of 4-NP by Fe-MABs followed…

Measurement of rotational relaxation in the ground state of methane perturbed by argon at low temperature

1999

International audience; Relaxation processes at low temperature in methane perturbed by argon have been investigated on the basis of new measurements. Diode laser absorption spectra of methane in the region of the dyad nu2/nu4 in supersonic expansions have been recorded. The time of relaxation of the ground state mean rotational energy was derived from the observed dependences of the rotational temperature on the concentration in the jet. A semi-classical model was used to calculate the state-to-state relaxation rate constants at room temperature. The evaluation of the time of relaxation of the mean rotational energy using semi-empirical temperature dependence laws is presented and discusse…

Towards sensory Langmuir monolayers consisting of macrocyclic pentaaminoanthraquinone

2014

A pentaazamacrocycle incorporating an intracyclic anthraquinone fragment (PENTAQ) was synthesized with the aim of forming metal-responsive Langmuir monolayers. PENTAQ allows a good discrimination by naked eye of copper ions in methanol–water solutions (50 : 50 v/v). Spectrophotometric investigations of the protonation and Cu2+ binding properties of PENTAQ were undertaken in order to gain a deeper insight into the pH-dependent speciation as well as the color changing process. PENTAQ monolayers at air/water and air/methanol–water interfaces were prepared according to the Langmuir procedure. The structure of the monolayers can be tuned by varying the pH of the aqueous subphase, since it was fo…

Interface-Assisted Sign Inversion of Magnetoresistance in Spin Valves Based on Novel Lanthanide Quinoline Molecules

2018

Molecules are proposed to be an efficient medium to host spin-polarized carriers, due to their weak spin relaxation mechanisms. While relatively long spin lifetimes are measured in molecular devices, the most promising route toward device functionalization is to use the chemical versatility of molecules to achieve a deterministic control and manipulation of the electron spin. Here, by combining magnetotransport experiments with element-specific X-ray absorption spectroscopy, this study shows the ability of molecules to modify spin-dependent properties at the interface level via metal–molecule hybridization pathways. In particular, it is described how the formation of hybrid states determine…

Temperature-dependent EXAFS study of the local structure and lattice dynamics in cubic Y2O3

2016

The local structure and lattice dynamics in cubic Y2O3were studied at the YK-edge by X-ray absorption spectroscopy in the temperature range from 300 to 1273 K. The temperature dependence of the extended X-ray absorption fine structure was successfully interpreted using classical molecular dynamics and a novel reverse Monte Carlo method, coupled with the evolutionary algorithm. The obtained results allowed the temperature dependence of the yttria atomic structure to be followed up to ∼6 Å and to validate two force-field models.

Rapid determination of lead in petrol by atomic absorption spectrometry of emulsified samples

1979

Excited State Tuning of Bis(tridentate) Ruthenium(II) Polypyridine Chromophores by Push-Pull Effects and Bite Angle Optimization: A Comprehensive Exp…

2013

The synergy of push-pull substitution and enlarged ligand bite angles has been used in functionalized heteroleptic bis(tridentate) polypyridine complexes of ruthenium(II) to shift the (1) MLCT absorption and the (3) MLCT emission to lower energy, enhance the emission quantum yield, and to prolong the (3) MLCT excited-state lifetime. In these complexes, that is, [Ru(ddpd)(EtOOC-tpy)][PF6 ]2 , [Ru(ddpd-NH2 )(EtOOC-tpy)][PF6 ]2 , [Ru(ddpd){(MeOOC)3 -tpy}][PF6 ]2 , and [Ru(ddpd-NH2 ){(EtOOC)3 -tpy}][PF6 ]2 the combination of the electron-accepting 2,2';6',2''-terpyridine (tpy) ligand equipped with one or three COOR substituents with the electron-donating N,N'-dimethyl-N,N'-dipyridin-2-ylpyridin…