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

## TL;DR

A new bent-core Schiff base ligand and its nickel complex were designed and studied for their DNA and protein binding properties.

## Contribution

The novel bent-core ligand with AIE behavior and its Ni(ii) complex show strong biomolecular binding potential.

## Key findings

- The ligand exhibits aggregation-induced emission behavior and forms a square-planar Ni(ii) complex.
- The complex shows strong binding affinity to DNA and serum proteins with low detection limits.
- Molecular docking confirms stable binding to BSA with a binding energy of −8.52 kcal mol−1.

## 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.

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.