Search results for "complex"
showing 10 items of 5889 documents
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 (…
Synthesis, spectroscopic, cyclic voltammetry properties and molecular structure of the thiocyanato-N meso-tetratolylporphyrinato zinc(II) ion complex
2017
International audience; This paper describes the synthesis of the (thiocyanato-N)(meso-tetratolylporphyrinato)zinc(II) chlorobenzene monosolvate complex with the formula [K(2,2,2-crypt)][Zn(TTP)(NCS)]·C6H5Cl (I) using the cryptand-222 to solubilize potassium thiocyanate in chlorobenzene solvent. Complex (I) has been characterized by elementary analysis, IR, UV–vis, 1H NMR and MS, and the structure of this new zinc(II) metalloporphyrin been examined crystallographically. A cyclic voltammetry investigation was also carried out on this species. The title compound crystallizes in the triclinic, space group P-1, with a = 11.5151(7) Å, b = 15.212(10) Å, c = 20.1093(12) Å, α = 80.428(4)°, β = 74.9…
Pyrazolium- and 1,2-Cyclopentadiene-Based Ligands as σ-Donors: a Theoretical Study of Electronic Structure and Bonding
2012
A high-level theoretical investigation of 1,2-cyclopentadiene (4) was performed using density functional theory and wave function methods. The results reveal that, in contrast to earlier assumptions, the ground state of this ephemeral “allene” is carbene-like with a small diradical component. Furthermore, the electronic structure and chemistry of 4 are found to parallel that of 1,2,4,6-cycloheptatetraene: both molecules possess a low-lying excited singlet state with a closed-shell carbenic structure, enabling rich coordination chemistry. Energy decomposition analyses conducted for currently unknown metal complexes of 4 as well as those involving stable carbenes based on the pyrazolium frame…
Cyclopentadienyl derivatives of octahedral carbonylcarbide hexaruthenium clusters: synthesis, NMR, IR and X-ray characterization
1996
Abstract The reaction of hexanuclear carbonylcarbide cluster Ru6C(CO)17 (1) with pentamethylcyclopentadiene by reflux in heptane leads to a new chelate cluster Ru6C(μ-η1-η5-CH2C5Me4)(CO)14 (2). The compound 2 contains a CH2 group α-bonded to one of the Ru atoms in the Ru6 cluster and a C5Me4-ligand η5-coordinated by the adjacent Ru atom of the Ru6 cluster. Reflux of 1 in hexane with two molecular equivalents of nickelocene, Ni(C5H5)2 NiCp2, used as a source of cyclopentadiene yields the Ru6C(CO)12Cp2 (3) cluster. The compounds 2 and 3 have been characterized by NMR and IR spectroscopy and their crystal structures determined by X-ray diffraction studies.