Thermal and Electrochemical Stability of Tetraglyme-Magnesium Bis(trifluoromethanesulfonyl)amide Complex: Electric Field Effect of Divalent Cation on Solvate Stability
Artikel i vetenskaplig tidskrift, 2016

Phase behavior of binary mixtures of tetraglyme (G4) and Mg[TFSA]2 (TFSA: bis(trifluoromethanesulfonyl)amide) was investigated. In a 1:1 molar ratio, G4 and Mg[TFSA]2 formed a stable complex with a melting point of 137 degrees C. X-ray crystallography of a single crystal of the complex grown from a G4-Mg[TFSA]2 binary mixture revealed that the G4 molecule wraps around Mg2+ to form a complex [Mg(G4)](2+) cation, and the two [TFSA](-) anions also participate in the Mg2+ coordination in the crystal. The thermal stability of [Mg(G4)][TFSA](2) was examined by thermogravimetry, and it was found that the complex is stable up to 250 degrees C. Above 250 degrees C, desolvation of the Mg2+ ion takes place and G4 evaporates. On the other hand, the weight loss starts at around 140 degrees C in solutions containing excess G4 (n > 1 in Mg[TFSA]2:G4 = 1:n) due to the evaporation of free (uncoordinated) G4. The suppression of G4 volatility in the [Mg(G4)][TFSA]2 complex is attributed to strong electrostatic and induction interactions between divalent Mg2+ and G4. In addition, complexation of G4 with Mg2+ is effective in enhancing the oxidative stability of G4. Linear sweep voltammetry revealed that the oxidative decomposition of [Mg(G4)][TFSA]2 occurs at electrode potentials >5 V vs Li/Li+, while the oxidation of uncoordinated G4 occurs at around 4.0 V. This oxidative stability enhancement occurs because the HOMO energy level of G4 is reduced by complexation with Mg2+, which is supported by the ab initio calculations.


S. Terada

Yokohama National University

Toshihiko Mandai

Yokohama National University

S. Suzuki

Yokohama National University

S. Tsuzuki

National Institute of Advanced Industrial Science and Technology (AIST)

K. Watanabe

Yokohama National University

Y. Kamei

Yokohama National University

K. Ueno

Yokohama National University

K. Dokko

Yokohama National University

Kyoto University

M. Watanabe

Yokohama National University

Journal of Physical Chemistry C

1932-7447 (ISSN) 1932-7455 (eISSN)

Vol. 120 3 1353-1365


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