Crystal structure investigation, spectroscopy, quantum chemical studies, and biological evaluation of a Ni(II)-based hybrid material

Over the last few decades, hybrid materials based on transition metal complexes and their wide variety of ligands have attracted increasing attention due to their multi-functionality, structural tunability, and wide range of biological and technological applications. In this study, the synthesis and structural characterization of a new complex compound [Ni(C₆H₉N₂)₂(H₂O)₄](SO₄)₂.4H₂O (abbreviated Ni-3AMP) were carried out. Single-crystal X-ray diffraction confirmed a triclinic crystal system with an octahedral Ni²⁺ coordination environment. Spectroscopic investigations, including FT-IR, UV–Vis, and photoluminescence analyses verified the presence of key functional groups including –OH, –NH₂, –C=C– etc. They revealed strong blue emission, with theoretical (DFT/CAM-B3LYP/LanL2DZ) calculations supporting the observed structural and electronic properties. The Hirshfeld surface analysis of Ni-3AMP shows that about 45 % of all the contacts are dominated by O⋯H type contacts, which are the hydrogen bond interactions of the C-H⋯O, N-H⋯O and O-H⋯O, type. The molecular docking simulation using two P. aeruginosa targets (7PTF and 7PTG) representing the ATPase domain of DNA gyrase subunit B demonstrated superior binding affinity with Ni-3AMP compared to ciprofloxacin (CIP), a standard antibacterial drug with binding affinities of −139.60 kJ/mol (7PTF@Ni-3AMP), −108.90 kJ/mol (7PTF@CIP), −130.27 kJ/mol (7PTG@Ni-3AMP), −110.84 kJ/mol (7PTF@CIP), and multiple hydrogen bonds of 11, 10, 5, 5 respectively. In vitro antimicrobial assays further revealed potent antibacterial activity, particularly against P. aeruginosa and E. coli, surpassing that of ciprofloxacin. These findings suggest that Ni-3AMP is a promising multifunctional agent with potential applications in biomedical therapeutics and optoelectronics.