Search results for "aqueous solution"
showing 10 items of 1610 documents
[Cr(dpa)(ox)2]–: a new bis-oxalato building block for the design of heteropolymetallic systems. Crystal structures and magnetic properties of PPh4[Cr…
2001
[EN] The new complexes of formulae PPh4[Cr(dpa)(ox)(2)] (1), AsPh4[Cr(dpa)(OX)(2)] (2), Hdpa[Cr(dpa)(ox)(2)]-4H(2)O (3), Rad[Cr(dpa)(ox)(2)] . H2O (4) and Sr[Cr(dpa)(ox)(2)](2) . 8H(2)O (5) [PPh4 = tetraphenylphosphonium cation; AsPh4 = tetraphenylarsoniurn cation; dpa = 2,T-dipyridylamine; ox = oxalate dianion; Rad = 2-(4-N-methylpyridinium)4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-a-oxyl-3-N-oxide] have been prepared and characterised by single-crystal X-ray diffraction. The structures of 1-4 consist of discrete [Cr(dpa)(ox)(2)](-) anions, tetraphenylphosphonium. (1), tetraphenylarsonium (2), monoprotonated Hdpa (3) and univalent radical (4) cations and uncoordinated water molecules (2-…
Magneto-structural correlations in Ni(ii) [2 × 2] metallogrids featuring a variable number of μ-aquo or μ-hydroxo extra bridges
2019
Four new [2 × 2] grid-type metallosupramolecular species have been obtained by using the ditopic 3,6-bis(2′-pyridyl)pyridazine ligand (dppn) and nickel(II) salts containing poorly coordinating anions. Three of them have the formula [Ni4(μ-dppn)4(μ-OH)2(μ-H2O)2]X6·nH2O [with X = ClO4− (1), NO3− (2) and CF3SO3− (3), and n = 6.5 (1), 14 (2) and 4 (3)]. Their crystal structure shows the same tetranuclear core, constituted by four six-coordinate metal ions and four dppn molecules. Two hydroxo groups and two water molecules efficiently interact forming two hydrated hydroxide (H3O2−) supramolecular bridging anions, further stabilizing the grid. The other compound, [Ni4(μ-dppn)4(μ-OH)3(μ-H2O)](ClO4…
Magnetic Excitations in Tetrameric Clusters of Polyoxometalates Observed by Inelastic Neutron Scattering. Evidence for Anisotropic Exchange Interacti…
1997
Magnetic excitations in tetranuclear clusters of exchange-coupled metal ions encapsulated by polyoxotungstate ligands (1) have been observed by inelastic neutron scattering (INS) in the salts K10[M4(H2O)2(PW9O34)2]·nH2O, where M2+ = Mn, Co, and Ni. INS provides a much deeper and more detailed insight into the nature of the magnetic coupling in these clusters than bulk techniques. In particular, anisotropic exchange interactions are evidenced in the ferromagnetic Co4 cluster.
Bipyridine based metallogels: an unprecedented difference in photochemical and chemical reduction in the in situ nanoparticle formation
2017
Metal co-ordination induced supramolecular gelation of low molecular weight organic ligands is a rapidly expanding area of research due to the potential in creating hierarchically self-assembled multi-stimuli responsive materials. In this context, structurally simple O-methylpyridine derivatives of 4,4′-dihydroxy-2,2′-bipyridine ligands are reported. Upon complexation with Ag(I) ions in aqueous dimethyl sulfoxide (DMSO) solutions the ligands spontaneously form metallosupramolecular gels at concentrations as low as 0.6 w/v%. The metal ions induce the self-assembly of three dimensional (3D) fibrillar networks followed by the spontaneous in situ reduction of the Ag-centers to silver nanopartic…
Asymmetric hydrogenation of ethyl pyruvate over aqueous dispersed Pt nanoparticles stabilized by a cinchonidine-functionalized β-cyclodextrin
2021
International audience; Cinchonidine-functionalized β-cyclodextrin was used as stabilizing agent for platinum nanoparticles dispersed in water, but also as chiral modifier for the asymmetric hydrogenation of ethyl pyruvate at 30 °C under 40 bar of hydrogen. This functionalized cyclodextrin allowed getting more stable, more catalytically active and also more enantioselective Pt nanoparticles compared to control catalytic systems. NMR and MALDI-MS analyses clearly showed the reduction of the vinyl group of the cinchonidine graft during the nanoparticles preparation. Under hydrogen pressure, the hydrogenation of the quinolinic moiety was also proven and can be responsible for the difficul…
Optical methods for the detection of heavy metal ions
2014
The review covers an important area of the modern chemistry, namely, the detection of heavy metal ions using optical molecular detectors. The role of this method in metal ion detection and the physicochemical grounds of operation of chemosensors are discussed, and examples of detection of most abundant heavy metal ions and synthetic approaches to molecular detectors are presented. The immobilization of molecular detectors on solid substrates for the design of analytical sensor devices is described. The bibliography includes 178 references.
The Role of Macrocyclic Receptors in Organization of Metal Centers
1994
The coordination properties of saturated aza or oxa-aza macrocyclic receptors are strictly dependent on their molecular topology. In order to rationalize the relationship between structural features and binding characteristics of such molecules we have studied the coordination behavior of different macrocyclic or macropolycyclic oxa-aza ligands towards metal cations. Depending on molecular topology, a variety of inorganic chemical species can be lodged inside the receptor’s cavity, such as simple metal ions, complexed inorganic anions, partially hydrated metal cations or binuclear assemblies.
Metal Complexes as Receptors
2017
The role played by metal complexes as receptors of different substrates is discussed. For this purpose, several relevant examples of the work performed by different research groups have been briefly discussed. The metal complexes have been organized attending to the molecular topology of the ligands employed. The article ends with the description of metallocages in which at least one of the metal ions constituting the cage framework binds the guest through coordinative bonds.
The use of emulsions in the preparation of samples and standards for analysis by atomic-absorption spectroscopy determination of Cu and Fe in mibk ex…
1984
The use of aqueous/organic emulsions is shown to give advantages in the AAS determination of Cu and Fe extracted as their pyrrolidinedithiocarbamate complexes into methyl isobutyl ketone. The emulsions are more stable than the extracts, and the standards can be prepared from aqueous solutions by emulsification, but without extraction.
Different approaches for the solar photocatalytic removal of micro-contaminants from aqueous environment: Titania vs. hybrid magnetic iron oxides
2019
Abstract This work reports on the light-induced heterogeneous photodegradation of four micro-contaminants (MCs): Carbamazepine (C), Flumequine (F), Ibuprofen (I), and Sulfamethoxazole (S), using two different heterogeneous advanced oxidation processes. The first one is the semiconductor photocatalysis, run in the presence of the suspension of a home prepared TiO2 (TiO2 HP); the second one is an heterogeneous photo-Fenton process run in the presence of a hybrid magnetic nanomaterial (MB3) with an iron oxides core and an organic shell made of bio-based substances (BBS) isolated from urban biowaste. The two materials work upon two different mechanisms and were already tested (and the action me…