Structures and Electronic Properties of Transition Metal-Containing Ionic Liquids: Insights from Ion Pairs

Abstract

Transition metal-containing ionic liquids (TM-ILs) have attracted a great deal of attention in recent years, due to their unique physical and chemical properties. In this work, several representative TM-ILs, such as the cations consisting of silver(I) center coordinated by two n-alkylimidazole ligands ([(C(n)(im))Ag(mim)](+)) and the anions involving mercury(II) (HgCl3(-)), zinc(II) (ZnCl3(-)), and rhenium(VII) (ReO4(-)), were investigated using density functional theory calculations. First, the structural and energetic properties of the ion pairs for these TM-ILs have been examined in detail and compared with properties for conventional ILs. It was found that the interactions between the cations and anions, including hydrogen bonds and electrostatic interactions, in TM-ILs become weaker in strength than those in traditional ILs. In particular, the calculated geometric and energetic features compare fairly well with the experimental results, such as melting points and X-ray crystal structures of these TM-ILs. Then, the structures and energetics of ion-pair dimers for three ILs containing HgCl3(-), ZnCl3(-), and ReO4(-) were also explored, to gain a deeper understanding of the properties of TM-ILs. Finally, a survey of the Cambridge Structural Database (CSD) was undertaken to provide some crystallographic implications of TM-ILs.

The acidity/basicity of metal-containing ionic liquids: insights from surface analysis and the Fukui function

“…35 Very recently, we have successfully utilized the B3LYP/aug-cc-pVDZ(-PP) method to study the structures and electronic properties of halogenated ILs and transition metal-containing ILs. 36,37 All the optimized structures were confirmed to be minima on the potential energy surface via vibrational frequency analysis at the same level of theory. All of these computations were carried out with the help of Gaussian 09 suite of programs.…”

Nanostructured Borate Halides for Optical Second Harmonic Generation at Surfaces

“…Their research shows that some obvious changes in electrostatic potential distribution were observed after introducing metal salts into the ILs. To be more specific, cation–anion interactions in these metal‐containing ILs are weaker than in pure ILs, according to the results of the electrostatic potential distribution analysis . We reasonably assume that ILs with weakened cation–anion interactions have higher reactivity.…”

“…After dissolution of metal salt in IL, characteristics of both the IL and the metal cation essentially change . Lu and co‐workers studied structures and electronic properties of metal‐containing ILs using electrostatic potential distribution analysis . Their research shows that some obvious changes in electrostatic potential distribution were observed after introducing metal salts into the ILs.…”

Application of Ionic Liquids in Pot-in-Pot Reactions

“…Compared to only about 600 molecular solvents currently used, approximately 10 18 ILs can be generated from possible combinations of various cations and anions [27]. As a result, ionic liquids are considered designer solvents because properties like; solubility, polarity, melting point, viscosity, and density, can be tailored to meet specific applications by varying the cation or anion [22,24,28]. Various studies have worked on understanding the structure-property relationship of these solvents in order to elucidate the dominant forces that impact their properties, enabling them to influence chemical reactivity.…”

“…Various studies have worked on understanding the structure-property relationship of these solvents in order to elucidate the dominant forces that impact their properties, enabling them to influence chemical reactivity. For instance, studies on the geometric and energetic properties on imidazolium cation-containing ILs have revealed that the anion prefers to reside over the imidazole ring forming a hydrogen bond with the acidic C 2 -H group [28]. Other non-covalent interactions like coulombic forces [29], van der Waals interactions [27] and π-π stacking [25] have been found to be key and dominate the behavior of ILs hence significantly influence their properties.…”