Crystallographic and computational investigation of a bent-core Schiff base Ni(ii) complex with DNA and protein binding studies

Abstract

The rational design and synthesis of a three-ring bent-core Schiff base ligand, (E)-4-(trifluoromethyl)phenyl-3-((4-butoxy-2-hydroxybenzylidene)amino)-2-methylbenzoate (HL), and its mononuclear Ni(II) complex, [Ni(L)₂] (1), are described. The presence of a polar –CF₃ group and a flexible butoxy chain imparts amphiphilic character to HL and induces aggregation-induced emission (AIE) behavior. Coordination with NiCl₂ yields a square-planar complex, as confirmed by spectroscopic methods, single-crystal X-ray diffraction analysis, and topological analysis. Fluorescence and SEM studies substantiate the aggregation propensity of HL. Density functional theory (DFT) and natural bond orbital (NBO) analyses reveal pronounced ligand-to-metal charge transfer in (1) and a moderate HOMO–LUMO gap of 4.00 eV, indicative of kinetic stability and optoelectronic relevance. Complex (1) exhibits strong binding affinity toward duplex DNA and serum proteins (BSA and HSA), evidenced by red-shifted fluorescence enhancement at 475 nm and low detection limits (0.075–0.188 µM). Molecular docking further supports stable BSA binding (−8.52 kcal mol⁻¹), highlighting the potential of this Ni(II) system for biomolecular recognition.