Novel Ni(II) coordination compounds containing phenanthroline derivatives and 3-carboxy-1-carboxymethyl-2-oxidopyridinium: synthesis, structure, and hirshfeld analysis

A novel Ni(II) coordination compound 1, [Ni(L)(CCP)]·2H2O, was synthesized under hydrothermal conditions using a combination of ligands with complementary coordination characteristics, where L = 2-(4-fluorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline and H2CCP = 3-carboxy-1-carboxymethyl-2-oxidopyridinium. The Ni(II) center adopts a distorted octahedral geometry with six coordination sites, consisting of two nitrogen atoms from the L ligand and four carboxylate oxygen atoms from two deprotonated CCP2- anions. The compounds are connected through π–π stacking interactions, forming a one-dimensional supramolecular chain. Through the C–H···π interactions between the CCP2⁻ anions and L ligands, the one-dimensional chains further assemble into a two-dimensional supramolecular layer. The compound (1) was characterized by photoluminescence (PL) spectroscopy and thermogravimetric (TGA) analysis. FT-IR analysis further supports the deprotonation of the carboxylic acid groups and their coordination with the Ni(II) center. Hirshfeld surface analysis quantitatively revealed the contributions of O···H/H···O, F···H/H···F, F···C/C···F, and π···π contacts, indicating their combined contribution to the ordered molecular packing and crystal stability. KEY WORDS: Coordination compound, Ni(II), Crystal structure, Hirshfeld surface analysis Bull. Chem. Soc. Ethiop. 2027, 41(1), 207-218. DOI: https://dx.doi.org/10.4314/bcse.v41i1.14