Anionic dependency of electronic and nonlinear optical properties of ionic liquids

• Published in: Journal of molecular liquids Vol. 345; p. 117030
• Main Authors: Bardak, Fehmi, Bardak, Cemile, Karaca, Caglar, Kose, Etem, Bilgili, Sibel, Atac, Ahmet
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2022
• Subjects: Density functional theory; Hyperpolarizability; Ionic liquid; Nonlinear optical properties; Density functional theory; Nonlinear optical properties; Hyperpolarizability; Ionic liquid
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2021.117030

[Display omitted] •First and second hyperpolarizabilities were obtained at M06-2X/aug-cc-PVTZ level.•Linear and NLO feature have strong anionic dependence.•Dipole polarizabilities have near perfect additive character.•Ionic liquids with more delocalized electron density have higher NLO potent. Nonlinear optical phenomena play significant roles in the bulk properties and responsive characteristics of ionic liquids, especially when used under strong electric fields. The variability of the anion-cation pair in ionic liquids makes them designer solvents; thus, the anion or cation dependency of the physicochemical properties should be understood in depth. Accordingly, the electric field-induced characteristics of eight ionic liquids with [Br]−, [BF4]−, [PF6]−, [Ac]−, [TFAc]−, [MS]−, [NTf2]−, and [Tos]− anions paired with the 1-butyl-3-methyl imidazolium cation were investigated using density functional theory modeling at four theoretical levels: B3LYP-6-31G(d), M06-2X 6-31G(d), M06-2X 6-311++G(d,p), and M06-2X aug-cc-PVTZ. The frontier molecular orbitals, electrostatic potential surface, and electron density difference maps were obtained to visualize the electrostatic characteristics. The permanent electric dipole moment, linear electric polarizability, and first-order and second-order hyperpolarizabilities were also determined. While the static dipole moment and dipole polarizabilities could be obtained using low-level quantum chemistry at a satisfactory level, the functionalization of more intensive methods was required to accurately obtain the nonlinear optical properties.