Crystal structure, intermolecular interactions and NLO properties for imidazolium hydrogen sulfate ionic liquid

Crystal structure, intermolecular interactions and nonlinear optical behavior for the ionic liquid imida-zolium hydrogen sulfate (ImHS) were presented in the current paper for the first time. This was achieved applying a combined experimental (single crystal X-ray diffraction) and theoretical (Quantum theory of atoms in molecules (QTAM), Hirshfeld surface (HS), natural bond orbital (NBO) analysis) method. The quantum chemical calculations were conducted via density functional theory at B3LYP/6-311 ++G(2d,2p) level. Important nonlinear optical parameters such as dipole moment (mu), polarizability (alpha), anisotropy of polarizability (A alpha) and first-order hyperpolarizability (beta) are calculated at B3LYP/6-311 ++G(2d,2p) level of theory as well.It was shown that fragments with different molecular geometry present in the ImHS structure. Forma-tion of hydrogen bonds (O middotmiddotmiddotH) between the imidazolium cation and hydrogen sulfate anion stabilizes the ImHS structure. It was confirmed by means of QTAM, HS and NBO, where intensive electron density dis-tribution between aromatic ring and inorganic anion due to O middotmiddotmiddotH interactions was registered. Pronounced charge transfers between imidazolium cycle and hydrogen sulfate anion were found to be responsible for highly polarizable nature of ImHS, registered as high values for mu, alpha and beta. Based on these, the studied ionic liquid was denoted as a good nonlinear optical material.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

The crystal structure, intermolecular interactions, and nonlinear optical behavior of the ionic liquid Imidazolium Hydrogen Sulfate (ImHS) were investigated for the first time. The combination of experimental (X-ray diffraction) and theoretical (quantum chemical calculations) methods provided important insights into the nonlinear optical properties of ImHS. The formation of hydrogen bonds between the imidazolium cation and hydrogen sulfate anion was found to stabilize the ImHS structure, leading to its highly polarizable nature and making it a promising candidate for nonlinear optical applications.