Search results for "element"
showing 10 items of 13601 documents
Synthesis and Characterization of Extended Bis(terpyridine)ruthenium Amino Acids
2009
(Oligopyridine)ruthenium(II) complexes have been widely used in dye sensitized solar cells and other sophisticated optical devices due to their outstanding photophysical properties and their chemical stability. Herein, we describe the longitudinal extension of our previously reported bis(terpyridine)ruthenium(II) amino acid [Ru(tpy–NH2)(tpy–COOH)]2+ (tpy = 4′-substituted 2,2′:6′,2″-terpyridine) by insertion of para-phenylene spacers –C6H4– between the terpyridine and the functional groups. The influence of the para-phenylene spacer on the absorption and emission properties is investigated using UV/Vis absorption and emission spectroscopy and is discussed within a qualitative molecular orbit…
Tin(IV), Monomethyltin(IV), and Dimethyltin(IV) Complexes with thiol sulfur and heterocyclic nitrogen donors: Molecular dynamics and structure by119S…
1995
The molecular dynamics of the complexes Sn(SPyN)4 (1), SnCl2(SPyN)2 (2), MeSn(SPy)3 (3), MeSnCl(SPyN)2 (4), Me2Sn(TCy)2 (5), Me2SnCl(TOx) (6), and Me2Sn(TUr) (7) [HSPy = 2-mercaptopyridine; HSPyN = 2-mercaptopyrimidine; HTCy = 2-thiocytosine; HTOx = 8-thioquinoline; H2TUr = 2-thiouracil] has been investigated by variable temperature 119Sn Mossbauer spectroscopy. The area under the resonant peaks has been determined as function of temperature, from which Debye temperatures and cut-off frequencies, as well as recoil-free fractions (Lamb Mossbauer factor) and mean square displacements of 119Sn, have been calculated. By fingerprint procedures on the basis of literature data, monomeric structure…
Coordination complexes of chromium(0) with a series of 1,3-diphenyl-6-arylfulvenes
2018
The synthesis and structural properties of a series of chromium tricarbonyl `piano-stool' complexes bearing substituted pentafulvene ligands were studied. The complexes, tricarbonyl(1,3,6-triphenylfulvene)chromium(0) benzene hemisolvate, [Cr(C24H18)(CO)3]·0.5C6H6 (I), tricarbonyl[1,3-diphenyl-6-(3-vinylphenyl)fulvene]chromium(0), [Cr(C26H20)(CO)3] (II), and tricarbonyl[1,3-diphenyl-6-(pyren-1-yl)fulvene]chromium(0), [Cr(C34H22)(CO)3] (III), each have a distorted octahedral geometry, with the fulvene coordinated in a π–η2:π–η2:π–η2 fashion. Significant deviation of the exocyclic fulvene double bond from the cyclopentadiene plane accompanies coordination. Evidence of non-covalent π–π interact…
Crystal structure of 2-methyl-1H-imidazol-3-ium aquatrichlorido(oxalato-κ2O,O′)stannate(IV)
2015
N—H⋯O, N—H⋯Cl and O—H⋯O hydrogen bonds between cations and anions in the complex salt (C4H7N2)+[Sn(H2O)Cl3(C2O4)]− are responsible for the formation of a three-dimensional network structure.
Synthesis of 4-amino-5-fluoropyrimidines and 5-amino-4-fluoropyrazoles from a β-fluoroenolate salt
2020
A synthesis of fluorinated pyrimidines under mild conditions from amidine hydrochlorides and the recently described potassium 2-cyano-2-fluoroethenolate was developed. A broad substrate scope was tested and mostly excellent yields were obtained. The synthesis of fluorinated aminopyrazoles from the same fluorinated precursor could be demonstrated but proceeded with lower efficiency.
Spin transition in heptanuclear star-shaped iron(III)–antimony(V) NCS- and CN-bridged compounds
2009
Abstract The precursor [FeIII(L)Cl] (LH2 = N,N′-bis(2′-hydroxy-benzyliden)-1,6-diamino-3-azahexane) has been prepared and Mossbauer spectroscopy assigned a high-spin (S = 5/2) state at room temperature. The precursor is combined with the bridging units [SbV(X)6]− (X = CN−, NCS−) to yield star-shaped heptanuclear clusters [(LFeIII–X)6SbV]Cl5. The star-shaped compounds are in general high-spin systems at room temperature. On cooling to 20 K some of the iron(III) centers switch to the low-spin state as indicated by Mossbauer spectroscopy, i.e. multiple electronic transitions. While the cyano-bridged complex performs a multiple spin transition the thiocyanate-compound shows no significant popul…
Iodine containing species in the remote marine boundary layer: A link to oceanic phytoplankton
2011
[1] Iodine containing species have been measured in the particle phase (PM2.5) and the gas phase during a ship campaign between January and February 2007 in the South Atlantic marine boundary layer (MBL). Methyl iodide (CH3I) in the gas phase and soluble iodine species, i.e. iodide, iodate and an unidentified organic iodine species (UOI), in PM2.5 were measured. Temporal variations of gaseous and particulate iodine species were investigated. The exposure of the sampled air masses to phytoplankton along the back-trajectories was studied using a lagrangian transport model and satellite observations of oceanic chlorophyll-a concentration. Significant correlations were found between the concent…
Mercury Speciation in Floodplain Soils and Sediments along a Contaminated River Transect
1998
A novel mercury-specific sequential extraction procedure (SEP) for the assessment of mercury (Hg) speciation in soils and sediments, with emphasis on studying the interaction between Hg and organic matter (OM), was developed and tested. It was applied to determine Hg speciation in floodplain topsoils and surface sediments along the Hg-contaminated part of the river Elbe, and to simultaneously derive some information on the (re)mobilization potentials for Hg from these matrices. The majority of the total Hg in the ecosystem today is bound in the floodplains, which also still geographically reflect the historic emission record. Most of the Hg in both matrices is bound strongly to OM, suggesti…
Carbon nanostructures incorporated on methacrylate monoliths for separation of small molecules by nano-liquid chromatography
2018
Abstract Carbon nanostructures have been incorporated to polymethacrylate monoliths to develop novel stationary phases with enhanced separation performance in nano-liquid chromatography (nano-LC). Two incorporation approaches of these nanomaterials in monoliths were investigated. Single-walled carbon nanohorns (SWNHs) were first incorporated to the polymerization mixture, followed by UV initiation. The resulting stationary phases with embedded SWNHs led to an increase in the separation performance of analytes compared to the parent monolith. Alternatively, a two-step photo-grafting approach was also adopted to attach the carbon nanoparticles onto the polymer monolith surface. The effect of …
An Insight into Substrate-Dependent Fluorination of some Highly Substituted Alicyclic Scaffolds
2017
The substrate-dependent fluorination of some highly-functionalized cyclopentane derivatives with multiple chiral centers has been investigated. The key steps of the stereocontrolled syntheses are the oxidative cleavage of the ring carbon–carbon double bond of readily available diexo or diendo norbornene β-amino acid derivatives followed by transformation of the resulted dialdehyde stereoisomers by reduction. Finally, substrate-directable chemodifferentiation of different types of hydroxy groups under fluorination procedures gave various densely functionalized alicyclic derivatives or heterocycles.