Deep eutectic solvents based on ammonium iodide and iodine possessing high electrical conductivity

Herein, we have demonstrated the preparation of deep eutectic solvents (DESs) using ammonium iodides and iodine. Binary mixtures of 10 ammonium iodides with iodine were examined, and methylammonium iodide [MeNH3]I, diethylammonium iodide [Et2NH2]I, butylammonium iodide [BuNH3]I, and dibutylammonium iodide [Bu2NH2]I formed liquid DESs when mixed with iodine within specific concentration ranges. The DESs showed high electrical conductivities, which increased with the iodine concentration. Among the DESs studied here, [MeNH3]I/I2 with the molar ratio of 1:2.5 showed a very high electrical conductivity (approximately 100 mS cm-1 at 298 K). Overall, the viscosity of the DES series decreased with increasing iodine concentration. The Walden plot showed that most DESs studied here were good electrical conductors, whereas [Bu2NH2]I/I2 DESs with the molar ratios of 1:0.75 and 1:1.00 were almost ideal electrical conductors. Raman spectra of the DESs [Bu2NH2]I/I2 mixtures showed the presence of polyiodides; thus the high electrical conductivity of the DESs in this study was attributed to the Grotthuss mechanism.

Automated summary

In this study, deep eutectic solvents (DESs) were prepared using ammonium iodides and iodine. Various mixtures of ammonium iodides with iodine were examined, and specific DESs with high electrical conductivities were formed. The viscosity of the DESs decreased with increasing iodine concentration. Raman spectra analysis indicated that the high electrical conductivity of the DESs was attributed to the Grotthuss mechanism.