Search results for "Complex."

Volume, energy and generalized energy of unit vector fields on Berger spheres: stability of Hopf vector fields

2005

We study to what extent the known results concerning the behaviour of Hopf vector fields, with respect to volume, energy and generalized energy functionals, on the round sphere are still valid for the metrics obtained by performing the canonical variation of the Hopf fibration.

Quantifying and Processing Biomedical and Behavioral Signals

2019

Synthesis, crystal structure and magnetic properties of a new cyanide-bridged mixed-valence copper(I)/copper(II) clathrate

2013

A unique cyanide-bridge mixed-valence CuI/CuII clathrate of formula [CuI2(CN)3][{CuII(tren)}2(μ-CN)](CF3SO3)2 [tren = tris(2-aminoethyl)amine] containing cyanide-bridged [{CuII(tren)}2(μ-CN)]3 + binuclear cations stacked between anionic honeycomb layered copper(I) cyanide networks, was synthesized and structurally characterized by single crystal X-ray diffraction. Variable-temperature magnetic susceptibility studies showed that the cyanide bridge mediates a strong antiferromagnetic interaction between the copper(II) centers (J = − 160 cm− 1, the spin Hamiltonian being defined as H = − JSA⋅SB).

Specific recognition of fluoride anion using a metallamacrocycle incorporating a uranyl-salen unit

2008

The design and synthesis of a novel fluoride receptor that uses a salen-complexed Lewis acidic uranyl center as the sole binding site is reported here. This receptor binds fluoride anions in DMSO with a high affinity constant (K > 106 M-1) and exhibits a negligible affinity (K < 10 M-1) towards otherwise effective competitors, such as acetate, phosphate and cyanide anions.

Reinforced cyclam derivatives functionalized on the bridging unit

2016

International audience; A new synthetic method has been developed for the preparation of reinforced cyclams (1,4,8,11-tetraazacyclotetradecane) C-functionalized on the bridging unit, by using a "one pot" reaction starting from the appropriate bis-aminal cyclam intermediate. The high reactivity of quaternized aminal moiety toward nucleophilic agent has been used to elaborate a new class of cross-bridged and side-bridged cyclam derivatives containing cyanide group on the ethylene bridge. Several chelators and corresponding copper(II) complexes have been prepared and characterized by X-ray diffraction. These new constrained polyazamacrocycles are valuable precursors of bifunctional chelating a…

Alternative Rieske Iron-Sulfur Subunits and Small Polypeptides of Cyanobacterial Cytochrome b 6 f Complexes

2016

The cytochrome (cyt) b6f complex is a central component of both, photosynthetic and respiratory electron- and proton transport processes in cyanobacteria. Among its eight bona fide subunits, the Rieske [2Fe-2S] protein is encoded by multiple genes in most cyanobacterial genomes. However, the significance of the resulting protein heterogeneity is essentially not yet understood. The following chapter provides an overview on the Rieske [2Fe-2S] protein diversity in cyanobacteria, and related aspects. In addition, potential roles of small cyt b6f complex subunits are discussed.

Limits and Criticalities of Predictions and Forecasting in Complex Social and Economic Scenarios: A Cybernetics Key

2014

Predictions play a key role in assuring the status of “rationality” in decisions. Nevertheless, in the field of social sciences and economics, predictions fail to correctly depict the oncoming scenarios. Why is it so difficult to achieve quantitative prediction of social and economic systems? Can science provide reliable predictions of social and economic paths that can be used to implement effective interventions? As in the notorious “El Farol bar problem” depicted by Brian Arthur (Am Econ Rev 84:406–411, 1994), the validity of predictive models is more a social issue than a matter of good mathematics. Predictability in social systems is due to limited knowledge of society and human behavi…

Nanowire iron(III) coordination polymer based on 1,2,4-triazolo[1,5-a]pyrimidine and chloride ligands

2019

Abstract The neutral ligand 1,2,4-triazolo[1,5-a]pyrimidine (tp) has been employed to prepare a new coordination compound of Fe(III), [FeCl3(tp)2]n (1). Compound 1 was investigated by single crystal X-ray diffraction and found to be a coordination polymer forming a ladder structure based on metal–ligand interactions, while H-bonding and aromatic interactions contribute to the supramolecular self-assembly into a 3D nanostructured material. The polymeric assembly is retained also in solution, where a metallo-supramolecular polymer based on coordinative metal–ligand binding is present, as shown by dynamic light scattering (DLS) measurements. The redox properties of the Fe(III) coordination pol…

Copper-Assisted Hemiacetal Synthesis: A Cu II Chain Obtained by a One-Step in situ Reaction of Picolinaldehyde

2014

International audience; The 1D polymer complex [Cu2(L)2(SCN)2]n (1 ) has been synthesised in a one‐step in situ reaction of picolinaldehyde with sodium thiocyanate. The complex 1 was characterised by FTIR spectroscopy, UV/Vis spectrophotometry and elemental analysis. The crystal structure of complex 1 shows that chains of dimer complexes are formed with tetra‐ and pentacoordinate copper centres alternately linked by one thiocyanato and two alkoxido bridges. Variable‐temperature magnetic measurements showed a strong antiferromagnetic interaction between the copper centres within the dimer mediated by the two alkoxido bridges with a J value of –374 cm–1, which is in agreement with the DFT‐cal…

New insights on the electronic, magnetic, electric and molecular structure of a bis-(4-cyanopyridine) iron(III) complex with the meso-tetrakis(4-meth…

2019

International audience; We have successfully synthesized and characterized a new low-spin iron(III) bis(4-cyanopyridine) complex with a meso-porphyrin substituted in the para positions of the phenyls by the methoxy group, namely the bis(4-cyanopyridine)[(meso-tetrakis(4-metoxyphenylporphyrinato)]iron(III) trifluoromethanesulfonate chlorobenzene monosolvate complex with the formula [FeIII(TMPP)(4-CNpy)2]SO3CF3.C6H5Cl (I). This species was characterized through ultraviolet–visible, Fourier-transform infrared and Mössbauer spectroscopy as well as by SQUID magnetometry, cyclic voltammetry, and X-ray crystallography. These characterizations indicated that our synthetic heme model is a low-spin (…