Structural characterization, Hirshfeld surface description and chemical reactivity for the new ionic liquid (C3H5N2)(HSeO4)

Crystal structure, intermolecular interactions and chemical reactivity for the new ionic liquid imidazolium hydrogen selenate (C3H5N2)(HSeO4) were evaluated in the present work for the first time. This was achieved via a number of techniques such as single crystal X-ray diffraction, Quantum theory of atoms in molecules (QTAIM), Hirshfeld surface (HS) and natural bond orbital (NBO) analysis). To optimized the molecular geometry of the title compound, density functional theory at B3LYP/6-311++G(2d,2p) basis set was applied. The ion pair (C3H5N2) (HSeO4) crystalized in a monoclinic system with a space group P2(1)/n and four molecules per unit cell. A hydrogen bond in the form of Se-1-O-2 center dot center dot center dot H-10-N-9 interaction stabilized (C3H5N2)(HSeO4) structure. While a linear geometry characterized Se-1-O-2 center dot center dot center dot H-10-N-9, fragments with trigonal pyramidal and angular-like geometry are present in (HSeO4) anion. Moieties with tetrahedral geometry in (C3H5N2) cation are registered. QTAIM and NBO revealed that H-10-N-9 bond is strongly covalent in nature, while O-2 center dot center dot center dot H-10 was primary electrostatic. Based on the HS analysis and enrichment ratio data, [N-H]center dot center dot center dot[O-Se], [O-H]center dot center dot center dot[O-Se] and [C-H]center dot center dot center dot[O-Se] bonds in (C3H5N2) (HSeO4) structure were noted as the most favored interactions. Intensive electron density distribution between (C3H5N2) and (HSeO4) fragments was responsible for high chemical reactivity of the studded compound. The latter was confirmed evaluating the frontier orbital gap and global reactivity descriptors (hardness, softness, electronegativity, chemical potential and electrophilicity index).