Search results for "Absorption"
showing 10 items of 2701 documents
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…
Acid Titrations of poly(dG-dC).poly(dG-dC) in Aqueous Solution and in a w/o Microemulsion
2005
The model polynucleotide poly(dG-dC).poly(dG-dC) (polyGC) was titrated with a strong acid (HCl) in aqueous unbuffered solutions and in the quaternary w/o microemulsion CTAB/n-pentanol/n-hexane/water. The titrations, performed at several concentrations of NaCl in the range 0.005 to 0.600 M, were followed by recording the modifications of the electronic absorption and of the CD spectra (210or = lambdaor =350 nm) upon addition of the acid. In solution, the polynucleotide undergoes two acid-induced transitions, neither of which corresponds to denaturation of the duplex to single coil. The first transition leads to the Hoogsteen type synG.C+ duplex, while the second leads to the C+.C duplex. The…
Neutral one-dimensional metal chains consisting of alternating anionic and cationic rhodium complexes.
2012
The metallophilic interactions were investigated within chains of oppositely charged rhodium carbonyl complexes. The cationic [Rh(CO)(2)(L)](+) (L = 2,2'-bipyridine and 1,10-phenanthroline) and anionic [RhCl(2)(CO)(2)](-) units were self-assembled into one dimensional rhodium chains supported by electrostatic interactions. The array of Rh centers in {[Rh(CO)(2)(2,2'-bpy)][RhCl(2)(CO)(2)]}(n) was found to be nearly linear with a Rh···Rh···Rh angle of 170.927(11)° and Rh···Rh distances of 3.3174(5) Å and 3.4116(5) Å. The crystal structure of {[Rh(CO)(2)(1,10-phen)][RhCl(2)(CO)(2)]} consisted of two sets of crystallographically independent chains with slightly different Rh···Rh···Rh angles (17…
Synthesis and spectral studies ofN-2-pyridinylcarbonyl-2-pyridinecarxoximidate copper(II) complexes
1987
Dimeric and polymeric copper(II) complexes containing BPCA (N-2-pyridinylcarbonyl-2-pyridinecarboximidate), having general formulae Cu(BPCA)X·nH2O (X=Cl, Br, NCS, NCO, N3, or CN) and Cu2(BPCA)2-X·nH2O [X=oxalate anion (OX), chloranilate anion (CA) or the dianion of 2,5-dihydroxy-1,4-benzoquinone (DHBQ)] have been synthesized by the copper(II)-assisted hydrolysis of 2, 4, 6-tris(2-pyridyl)-1, 3, 5-triazine. Spectroscopic results indicate five-coordinate, approximately square-pyramidal, geometry around the copper(II) ion. Half-field absorption in the ΔMs=±2 region of the X-band e.p.r. powder spectra has been observed for the dimeric species.
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.
Pyrolysed cork-geopolymer composites: A novel and sustainable EMI shielding building material
2019
Abstract In this investigation, and for the first time, pyrolysed sustainable cork was used to produce waste-based geopolymer-cork composites with enhanced electromagnetic interference (EMI) shielding properties. The influence of the pyrolysed cork amount and the geopolymer porosity on the EMI shielding ability of the composites was studied. The maximum total shielding effectiveness (SET) values achieved by these novel building materials (−13.8 to −15.9 dB) are equal to any other reported geopolymer microwave (MW) absorbers over the X-band, despite containing much lower carbon content. In addition, our composites were produced using an industrial waste (biomass fly ash) as raw material and …
On the Ion-Pair Recognition and Indication Features of a Fluorescent Heteroditopic Host Based on a BODIPY Core
2014
A fluorescent heteroditopic host for ion pairs and zwitterionic species has been synthesized. Its affinity towards a series of anions, cations and ion pairs in acetonitrile has been assessed, and the spectroscopic response has been evaluated. Solid–liquid extraction experiments of inorganic salts, α-amino acids and γ-aminobutyric acid (GABA) into acetonitrile solutions were performed, and the resulting complexes were analyzed by UV/Vis absorption, fluorescence and 1H NMR spectroscopy. The discrimination patterns observed have been rationalized in terms of the molecular topologies of the host and guests.
Uptake and bioavailability of persistant organic pollutants by plants grown in contaminated soil
2005
This paper assesses the uptake of persistent organic pollutants (POP's) into plants. In particular, uptake of alpha-endosulfan, beta-endosulfan and endosulfan sulfate from lettuce. The lettuce plants were grown on compost that had previously been contaminated at 10 and 50 microg g(-1) per POP. The soil was slurry spiked by adding the appropriate amount of POP in acetone in an approximate ratio of 1 ratio 2, w/v soil ratio solvent. The solvent was left to evaporate at ambient temperature for 24 hours. Lettuce plants were grown under artificial daylight for 12 hours a day. The influence of soil ageing on the recovery of POP's from spiked soil samples was also assessed. The average recovery of…
A SIMPLE PARTICLE MODEL FOR A SYSTEM OF COUPLED EQUATIONS WITH ABSORBING COLLISION TERM
2011
We study a particle model for a simple system of partial differential equations describing, in dimension $d\geq 2$, a two component mixture where light particles move in a medium of absorbing, fixed obstacles; the system consists in a transport and a reaction equation coupled through pure absorption collision terms. We consider a particle system where the obstacles, of radius $\var$, become inactive at a rate related to the number of light particles travelling in their range of influence at a given time and the light particles are instantaneously absorbed at the first time they meet the physical boundary of an obstacle; elements belonging to the same species do not interact among themselves…
H-Point standard additions method for resolution of binary mixtures with simultaneous addition of both analytes
1995
Abstract The basis of the H-point standard additions method, HPSAM, with simultaneous addition of both analytes is proposed for the resolution of binary mixtures. It is a modification of the previously described H-point standard additions method that permits the resolution of both species from a unique calibration set by making the simultaneous addition of the two analytes. The method uses as analytical signals the absorbances at pairs of wavelengths where each species shows the same absorbance. The required data to apply the method are the absorbance values at the previously selected wavelengths for the sample alone and spiked with both species at known concentrations. Linear relations bet…