On the Mechanism of the Iodide-Triiodide Exchange Reaction in a Solid-State Ionic Liquid

GROSSI, JOÁS; KOHANOFF, JORGE J.; ENGLISH, NIALL J.; BRINGA, EDUARDO M.; DEL PÓPOLO, MARIO G.

JOURNAL OF PHYSICAL CHEMISTRY B - (Print)

AMER CHEMICAL SOC

Año: 2017 vol. 121 p. 6436 - 6441

1520-6106

Efficient charge transport has been observed in iodide-based room-temperature ionic liquids when doped with iodine. To investigate preferred pathways for the iodide (I-)-to-triiodide (I3 -) exchange reaction and to clarify the origin of this high ionic conductivity, we have conducted electronic structure calculations in the crystal state of 1-butyl-3-methylimidazolium iodide ([BMIM][I]). Energy barriers for the different stages of the iodine-swapping process, including the reorientation of the I-⋯I3 - moiety, were determined from minimum energy paths as a function of a reaction coordinate. Hirshfeld charges and structural parameters, such as bond lengths and angles, were monitored during the reaction. Several bond-exchange events were observed with energy barriers ranging from 0.17 to 0.48 eV and coinciding with the formation of a twisted I-⋯I3 - complex. Striking similarities were observed in the mechanics and energetics of this charge-transfer process in relation to solid-state superionic conductors.