A Unique Pentafurcated Hydrogen Bonding in a Salt of Imidazolinone: Synthesis, Crystal Structure and Hirshfeld Surface Analysis of Three Imidazolinone Derivatives

Crystal structures of one imidazolinone based ligand L and one perchlorate salt (Salt 1) and one nitrate salt (Salt 2) of L have been reported. All the compounds were characterized with different spectroscopic tools such as NMR spectroscopy, mass spectroscopy and IR spectroscopy. The detailed elucidation of their solid-state structures was achieved through single crystal X-ray diffraction, offering comprehensive insights into their molecular arrangements. In their crystal structure, the asymmetric unit of L contains the whole molecule while in salt 2 the asymmetric unit contains one protonated L (HL+) and one nitrate ion. The crystallographic asymmetric unit of salt 1 comprises a solitary diprotonated L (H2L2+) ion. Various non covalent interactions including bi and trifurcated intermolecular motifs are observed in case of L and in salt 1 while unique rare pentafurcated C–H⋯O/N–H⋯O intermolecular motifs are observed in salt 2 which was further supported by computational studies. Besides these interactions, C–H⋯O, C–H⋯π and O⋯π intermolecular interactions are also present in the crystal structures. UV-Vis absorption spectra show absorption of all of them around 420 nm. Steady state fluorescence spectra show that all the three compounds emit blue light. Hirshfeld surface analysis and 2D-FP analysis were used to quantitatively explore the noncovalent interactions responsible for crystal packing.