Spectroscopic and Electrochemical Analyses for Neodymium Complexes in Potassium Bis(trifluoromethylsulfonyl)amide Melts. Issue 8 (3rd June 2017)

• Record Type: Journal Article
• Authors: Matsumiya, Masahiko; Ota, Hisashi; Kuribara, Keita; Tsunashima, Katsuhiko
• Is Part Of: Journal of the Electrochemical Society. Volume 164:Issue 8(2017)
• Page Start: H5230
• Page End: H5235
• Publication Date: 2017-06-03
• Subjects: Bis(trifluoromethyl-sulfonyl)amide -- Diffusion coefficient -- Neodymium complex -- Raman spectroscopy; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0361708jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : The coordination states of the multivalent neodymium complexes in potassium bis(trifluoromethyl-sulfonyl) amide; K[TFSA] were investigated by Raman spectroscopy. The concentration dependences of deconvoluted Raman spectra were investigated for 0.23–0.45 mol kg −1 Nd(III), and mixed sample of Nd(II)/Nd(III) = 1/3 at the molar ratio in K[TFSA]. According to the conventional analysis, the solvation number; n of neodymium complexes were determined to be n = 4.06 for Nd(II), 5.02 for Nd(III). Moreover, thermodynamic properties such as Δiso G, Δiso H, and Δiso S for the isomerism of [TFSA] − from trans- to cis- coordinated isomer were evaluated from temperature dependence of Raman bands. In the first solvation sphere of Nd 3+ cation, Δ iso H (Nd) became remarkably negative, suggesting cis -[TFSA] − isomers were stabilized by enthalpic contributions. Then, Δ iso H (Nd) contributed to the remarkable decrease in Δ iso G (Nd), and this result clearly indicates cis -[TFSA] − conformers bound to Nd 3+ cations are preferred coordination state of [Nd (III) ( cis -TFSA)5 ] 2− . Furthermore, the electrochemical analysis revealed the reduction process proceeded in two steps; [Nd (III) (TFSA)5 ] 2− + e − → [Nd (II) (TFSA)4 ] 2− + [TFSA] − and [Nd (III) (TFSA)5 ] 2− + 3e − → Nd(0) + 5[TFSA] − . The diffusion coefficient of [Nd (II) (TFSA)4 ] 2− was larger than that of [Nd (III) (TFSA)5 ] 2− on the range of whole temperature. The activation energies of [Nd (II) (TFSA)4 ] 2− and [Nd (III) (TFSA)5 ] 2− were 29.5 kJ mol −1 and 49.8 kJ mol −1, respectively.