Electrode process of La(Ⅲ) in molten LiCl-KCl

The electrode process of La(Ⅲ) at Mo electrode in the molten LiCl-KCl for temperatures ranging from 683 K to 773 K was studied by cyclic voltammetry and chronopotentiometry,respectively.The results showed that in the molten LiCl-KCl,reduction of La(Ⅲ) occurred in a step with a global exchange of three electrons.Cyclic voltammetry studies indicated that at a sweep rate lower than 0.2 V/s,the electroreduction of La(Ⅲ) to lanthanum metal was reversible and controlled by diffusion of La(Ⅲ).However,the process b...

Tetravalent Terbium Chelates: Stability Enhancement and Property Tuning

Coordination chemistry of rare-earth elements has been dominated by the+3 oxidation state.Complexes with higher-valence lanthanide ions are synthetically challenging but are of fundamental research interest and significance as advanced molecular materials.Herein,four tetravalent terbium complexes(2-5)of the common formula[Tb(OSiPh3)4L](L=ethylene glycol dimethyl ether(DME),2,2’-bipyridine(bpy),2,2’-bipyrimidine(bpym),and 1,10-phenanthroline(phen))are reported.Crystallographic analyses reveal in each of these complexes a hexacoordinate Tb(IV)ion situated in a distorted octahedral coordination environment formed by four triphenylsi-loxido ligands and a bidentate chelating ligand.The use of chelating ligands enhances the stability of the resulting complexes over their THF solvate precursor.More significantly,the aromatic N-chelating ligands have been found to tune effectively the electronic structures of the complexes,as evidenced by the sizable potential shifts observed for the quasi-reversible redox Tb(IV/III)process and by the changes in their absorption spectra.The experimental findings are augmented with quantum theoretical calculations in which the ligandπ-donation to the 5d orbitals of the Tb(IV)center is found to be primarily responsible for stability enhancement and the corresponding changes of physical properties observed.Magnetic measurements and results from electron paramagnetic resonance studies produced small absolute values of zero-field splittings of these complexes,ranging from 0.1071(22)to 1.1484(112)cm-1 and comparable to the values reported for analogous Tb(IV)complexes.

Electrochemical behavior of cerium ion in molten LiCl-KCl

The electrode process of cerium（III） on the Mo electrode in eutectic LiC1-KC1 melt was investigated by electrochemical transient techniques in the temperature range of 673-783 K, respectively. These results unanimously indicated that the reduction proc- ess of cerium（III） to cerium metal was a single step exchanging three electrons which was controlled by diffusion of cerium（III）. Dif- fusion coefficients （Dce0II）） in eutectic LiC1-KC1 melt were determined by cyclic voltammetry, chronopotentiometry and square wave voltammetry. An empirical diffusion coefficient function depending on temperature was proposed： lnDce（Ⅲ）--2.129-5704/T. The formal potentials （E^θCe（Ⅲy/Ce（0） versus Ag/AgCl reference electrode） at different temperatures were obtained from chronopotentiometry, which were --2.10 V （673 K） and -2.07 V （733 K）, respectively.