Microstructure, dynamics and optical properties of metal-doped imidazolium-based ionic liquids

Abstract

In this paper we study the complexation of Al3+ and several transition metals (Cr3+, Fe3+, Mn2+, Ni2+) in the ionic liquid 1-butyl-3-methylimidazolium thiocyanate. New insights into the structure, single-particle dynamics and electronic properties (optical absorption spectra) of these bulk mixtures are provided by molecular dynamics and density functional theory calculations, and our results are successfully compared with available experimental data. Our theoretical results reveal the existence of a bridging coordination mode between neighboring metal-ligand complexes in the polar nanoregions, and a scarce influence of the apolar nanoregions in the single-particle dynamics of the species in the mixture. Moreover, most part of the relevant features of the UV–Vis optical absorption spectra of these systems is properly explained by our density functional theory calculations for isolated complexes in the gas phase, evidencing that ionic liquid cations play only a limited role in the complex electronic properties.