Search results for "ion chemistry"
showing 10 items of 254 documents
Solution Chemistry of Element 106: Theoretical Predictions of Hydrolysis of Group 6 Cations Mo, W, and Sg
2001
Fully relativistic molecular density-functional calculations of the electronic structure of hydrated and hydrolyzed complexes have been performed for the group 6 elements Mo, W, and element 106, Sg. By use of the electronic density distribution data, relative values of the free energy changes and constants of hydrolysis reactions were defined. The results show hydrolysis of the cationic species with the formation of neutral molecules to decrease in the order Mo > W > Sg, which is in agreement with experiments for Mo, W, and Sg. For the further hydrolysis process with the formation of anionic species, the trend is reversed: Mo > Sg > W. A decisive energetic factor in the hydrolysis process …
Synthesis and characterization of novel quinolyl porphyrins as receptors. Study of their association with halophenols and 4nitrophenol as a reference
2020
International audience; In this work, new receptors built on the porphyrin scaffold were synthesized for halophenols recognition. A quinolyl group was introduced on the porphyrin's periphery as binding site, to form two series of molecules based on two distinct porphyrin frames and which were obtained in free base and zinc forms. The binding between these porphyrin based receptors and halophenols (2,3,4,6tetrachlorophenol, 2,4,6-trichlorophenol or 2,4,6-tribromophenol) was studied. As established by 1 H NMR spectroscopy, the binding constants are in the range of two-digit numbers, which value is correlated with the porphyrin structure (substitutive pattern, form of the free base or Zn II co…
New CpCrCl2(PR3) complexes: physical properties and reduction chemistry
1998
Abstract Compounds CpCrCl2L ( L = PMe 2 Ph , 1 , PMePh 2 , 2 ; PPh 3 , 3 ) have been prepared. Their magnetic moment is in accord with the presence of three unpaired electron and a variable temperature 1H NMR investigation of 1 shows Curie-Weiss behavior. The 1H NMR, EPR and UV-visible spectra are in agreement with those of other previously reported compounds of the same family. An electrochemical investigation shows the accessibility of an irreversible reduction process. A parallel sodium reduction investigation of complexes CpCrCl2L (L = PMe3 and η1-dppe) suggests tjat the reduction process is followed by immediate chloride loss, and then by a ligand redistribution process to afford chrom…
Mixed Titanium–Hafnium Chloridometallate Complexes
2007
The addition of either NEt 3 BzCl or [Ph 3 PNPPh 3 ]Cl (1 equiv. chloride per metal) to a 1:1 mixture of HfCl 4 and TiCl 3 in SOCl 2 results in Ti oxidation and leads to the corresponding salts of the [TiHfCl 10 ] 2- ion. A solution IR investigation in the v(M-Cl) region indicates that this ion is in equilibrium with the homodimetallic [Ti 2 Cl 10 ] 2- and [Hf 2 Cl 10 ] 2- ions. An X-ray study of the NEt 3 Bz + salt reveals an edge-sharing bioctahedral dianion sitting on a crystallographic inversion centre. The crystal is a solid solution of different species with compositional disorder at the metal site, each metal position having the occupancy Ti 0.685 Hf 0.315 . The M-M and M-Cl distance…
Thermodynamic and kinetic control over the oxidation mechanism of the natural vanadyl porphyrin series (DPEP)VO in methylene chloride: electrogenerat…
2006
The electrochemical behavior of the natural (DPEP)VO series (where DPEP is the dianion deoxophylloerythroetioporphyrinate) is studied in methylene chloride. The investigated compounds, which were extracted from oil shales of Tarfaya (Morocco), exhibit a typical electrochemical behavior as compared to that of related synthetic vanadyl porphyrins. The electro-oxidation of (DPEP)VO is characterized by a splitting of the peaks when carried out at a glassy carbon electrode. This can be explained by two possible paths (CE and EC mechanisms) which are characterized by a “square diagram” where the chemical step, C, corresponds to a dimerization (radical–radical or substrate–substrate reaction). The…
High oxidation state aqueous organometallics: synthesis and structure of a dinuclear oxo(pentamethylcyclopentadienyl)acetato complex of molybdenum(IV…
2003
International audience; The zinc reduction of Cp*2Mo2O5 in a MeOH–H2O mixture in the presence of acetic acid affords the diamagnetic dinuclear compound [Cp*MoO(O2CCH3)]2. An X-ray structural investigation reveals a novel dioxo- and diacetato-bridged structure, with a relatively strong metal–metal bond [2.5524(3) Å]. The compound exhibits a reversible one-electron oxidation process in the cyclic voltammogram. A comparison with other related structures reveals the effect of the electric charge on the mononuclear or dinuclear structural choice.Zinc reduction of Cp*2Mo2O5 in water–methanol in the presence of acetic acid affords compound Cp*2Mo2O2(O2CCH3)2, whose dinuclar tetrabridged structure …
Solvent, anion and structural effects on the redox potentials and UV-visible spectral properties of mononuclear manganese corroles
2008
A series of manganese(III) corroles were investigated as to their electrochemistry and spectroelectrochemistry in nonaqueous solvents. Up to three oxidations and one reduction were obtained for each complex depending on the solvents. The main compound discussed in this paper is the meso-substituted manganese corrole, (Mes 2PhCor)Mn, and the main points are how changes in axially coordinated anion and solvent will affect the redox potentials and UV-vis spectra of each electrogenerated species in oxidation states of Mn(III), Mn(IV), or Mn(II). The anions OAc (-), Cl (-), CN (-), and SCN (-) were found to form five-coordinate complexes with the neutral Mn(III) corrole while two OH (-) or F (-)…
Radiation-Engineered Functional Nanoparticles in Aqueous Systems.
2015
Controlled synthesis of nanoscalar and nanostructured materials enables the development of novel functional materials with fine-tuned optical, mechanical, electronic, magnetic, conductive and catalytic properties that are of use in numerous applications. These materials have also found their potential use in medicine as vehicles for drug delivery, in diagnostics or in combinations thereof. In principle, nanoparticles can be divided into two broad categories, organic and inorganic nanoparticles. For both types of nanoparticles there are numerous possible synthetic routes. Considering the large difference in nature of these materials and the elementary reactions involved in the synthetic rout…
Gas-phase ion chemistry of protonated melatonin
2009
The gas-phase ion chemistry of protonated melatonin has been investigated by mass spectrometric (MS) techniques involving chemical ionisation, fast atom bombardment and electrospray ionisation. Either naturally-occurring or collision-induced decomposition experiments have been carried out using side chain tetra-deuterium-labelled derivatives, as well as the corresponding N–D derivatives obtained by exchange with D2O. The analysis of experimental results allows definite pathways for the formation of the ion at m/z 174 to be assigned and sheds some more light on the overall fragmentation pathways. Experiments on labelled derivatives evidenced H–D scrambling processes during fragmentation.
Polymerization reactions and modifications of polymers by ionizing radiation
2020
International audience; Ionizing radiation has become the most effective way to modify natural and synthetic polymers through crosslinking, degradation, and graft polymerization. This review will include an in-depth analysis of radiation chemistry mechanisms and the kinetics of the radiation-induced C-centered free radical, anion, and cation polymerization, and grafting. It also presents sections on radiation modifications of synthetic and natural polymers. For decades, low linear energy transfer (LLET) ionizing radiation, such as gamma rays, X-rays, and up to 10 MeV electron beams, has been the primary tool to produce many products through polymerization reactions. Photons and electrons in…