Search results for " metal"
showing 10 items of 2159 documents
Malonate-based copper(II) coordination compounds: Ferromagnetic coupling controlled by dicarboxylates
2003
Studies on structural and magnetic properties of polynuclear transition metal complexes, aimed at understanding the structural and chemical factors governing electronic exchange coupling mediated by multiatom bridging ligands, are of continuing interest to design new molecular materials exhibiting unusual magnetic, optical and electrical properties, bound to their molecular nature. Looking at potentially flexible bridging ligands, the malonate group seems a suitable candidate. The occurrence of two carboxylate groups in the 1,3 positions allows this ligand to adopt simultaneously chelating bidentate and different carboxylato bridging modes (syn–syn, anti–anti and syn–anti trough one or two …
Functionalized Tri‐ and Tetraphosphine Ligands as a General Approach for Controlled Implantation of Phosphorus Donors with a High Local Density in Im…
2014
Supported phosphine ligands are auxiliaries of topical academic and industrial interest in catalysis promoted by transition metals. However, both controlled implantation and controlled conformation of ligands should be achieved to produce immobilized catalysts that are able to structurally “copy” efficient homogeneous systems. We provide herein a general synthetic strategy for assembling a new class of branched tetra- and triphosphine ligands with a unique controlled rigid conformation, and thus providing a high local density of phosphorus atoms for extended coordination to the metal center. We prepared new functionalized cyclopentadienyl (Cp) salts to design polyphosphines that were “ready…
In vitro evaluation of leishmanicidal properties of a new family of monodimensional coordination polymers based on diclofenac ligand
2020
Some series of isostructural chains with general formula [M(diclof)(HO)]·(EtOH) have been obtained from reaction between diclofenac ligand (diclof) and first row transition salts (M = Mn (1),Ni (2) and Co (3)). These monodimensional coordination polymers have been characterized and their crystal structures have been solved by X-ray diffraction methods, elucidating isostructural compounds that are chains with water molecules acting as bridge between different metallic centers, while diclofenac ligands are coordinated to the octahedral coordination environment of the same. Magnetic studies of these complexes have revealed the existence of moderate ferromagnetic interactions among manganese, n…
Anomalous diffraction profiles of alkali-halide-alkali-cyanide mixed crystals.
1986
The x-ray diffraction profiles of four mixed alkali halides-alkali cyanides have been studied. At the threshold concentration where the systems change over from ferroelastic ordering to the glass state, the profiles are highly unusual. The diffracted intensity of transverse scans along the cubic axes follows $I\ensuremath{\sim}\mathrm{exp}(\ensuremath{-}\ensuremath{\alpha}|\ensuremath{\xi}|)$, where $\ensuremath{\xi}$ is the reduced wave vector, measured from the line center.
Chemistry of transition-metal clusters with mixed Sb/S ligands: evidence for a terminal Sb=S double bond in Cp*3Rh3Sb2S5 (Cp* = C5Me5).
2005
The reaction of [Cp 2 *Rh 2 Cl 4 ] (Cp* = C 5 Me 5 ) with a slight excess of K 3 SbS 3 in boiling THF gave the neutral clusters [Cp* 4 Rh 4 S 5 ] (1), [Cp* 3 Rh 3 Sb 2 S 5 ] (2), and after salt metathesis [Cp* 3 Rh 3 SbS n ]PF 6 (3; n = 5 and 6). The structures of 1-3 are heterocubane clusters with Cp*Rh, S, and Sb vertices but with sulfur inserted into one (1 and 2) or two (3) edges. X-ray diffraction analysis of 2 additionally reveals a very short Sb-S distance of 2.297(1) A within the novel μ 3 -Sb 2 S 4 ligand. Density functional theory calculation of the model compounds [SSbS] 3 - , [HSSbS] 2 - , and [HSSbH 2 S] 0 provided strong evidence for the existence of a stable terminal Sb=S dou…
Designing conjugated microporous polymers for visible light-promoted photocatalytic carbon–carbon double bond cleavage in aqueous medium
2018
The production of valuable carbonyl compounds directly from alkenes via carbon–carbon double (CC) bond cleavage is a highly important reaction. As a promising alternative to traditional metal-catalyzed thermal reaction conditions, photocatalysis offers an environmentally friendly and sustainable synthetic strategy. However, most photocatalysts used so far were homogeneous, molecular and transition metal-based catalytic systems. Here, we report a structural design strategy of conjugated microporous polymers (CMPs) as a class of metal-free, heterogeneous, stable and reusable photocatalysts for visible light-promoted CC bond cleavage reaction. Via different electron donor and acceptor combinat…
The abundance of Au, Pt, Pd, and the mode of heavy metal fixation in highly polluted sediments from the Rhine River near Mainz, West Germany
1984
The Au, Pt and Pd contents of the sediments of Ginsheimer‐Altrhine River, a channel of the Rhine river which drains one of the most industrialized regions of western Europe, have been determined by flameless atomic absorption spectrophotometry. The abundances of these noble metals range from 96–460 ppb Au; 734 ppb‐31 ppm Pt and 32 ppb‐4 ppm Pd. The extremely high concentrations, particulary those of Pt and Pd, are attributed to their use in industry and are due to the formation and concentration of metal‐organic complexes, mainly at the interface between an extremely reducing and an oxidizing aquatic environment. Differential thermal analyses of the polluted sediments in comparison to the p…
Rheological Behaviour, Mechanical Properties and Processability of Biodegradable Polymer Systems for Film Blowing
2017
Films for agricultural or packaging applications are typically made of low density polyethylene (LDPE). They are produced through the film blowing process, which requires the use of polymers with suitable rheological properties. Furthermore, the short shelf-life which is often related to many packed products leads to huge amounts of plastic-based wastes. This suggests the use of biodegradable and/or compostable polymers in replacement for traditional ones. To this regard, only few data exist on the rheological properties of biodegradable polymers undergoing film blowing processing. In this work, a detailed investigation on the rheological, mechanical and processability behaviour of some bio…
Counterion influence on the N–I–N halogen bond
2015
A detailed investigation of the influence of counterions on the [N–I–N]+ halogen bond in solution, in the solid state and in silico is presented. Translational diffusion coefficients indicate close attachment of counterions to the cationic, three-center halogen bond in dichloromethane solution. Isotopic perturbation of equilibrium NMR studies performed on isotopologue mixtures of regioselectively deuterated and nondeuterated analogues of the model system showed that the counterion is incapable of altering the symmetry of the [N–I–N]+ halogen bond. This symmetry remains even in the presence of an unfavorable geometric restraint. A high preference for the symmetric geometry was found also in …