Synthesis, characterization, crystal structure, Hirshfeld surface analysis, and theoretical study on a N-heterocyclic carbene salt and two NHC-palladium complexes

An N-ethylphthalimide functionalized 1,3-dialkylbenzimidazolium salt has been synthesized and characterized by elemental analysis, FTIR, H-1 NMR, and C-13 NMR spectroscopy. Crystal structures of the salt and two palladium complexes were determined by single-crystal X-ray diffraction studies. Theoretical calculations were obtained by density functional theory (DFT) methods at the HSEh1PBE/SDD level of theory. Structural parameters of the compounds are well represented by DFT calculations. Noncovalent interactions in the compounds have also been studied through two-dimensional fingerprint plots based on Hirshfeld surface analysis. Frontier molecular orbitals (HOMO-LUMO) and their energy gap were determined to explore the stability of the molecules. The large HOMO-LUMO energy gaps point out a high kinetic stability of the compounds in their electron transfer.