Synthesis, characterization, anti-nematicidal, and computational study of Copper(II) complex derived from fluoro-substituted Schiff base ligand

Abstract

In this study, a novel fluoro-substituted Schiff base ligand (HL) was synthesized through a condensation reaction between 2-bromo-4-(trifluoromethoxy)aniline and 2-hydroxybenzaldehyde in methanol solvent at room temperature. The ligand was subsequently reacted with copper(II) acetate to produce the corresponding Cu(II) complex (CuL2). Both the ligand and its complex underwent characterization using various techniques including nuclear magnetic resonance, ultraviolet-visible, Fourier-transform infrared, thermogravimetric analysis, elemental analysis, and mass spectroscopy. In addition, the solid-state structure of the complex was determined through single crystal X-ray diffraction analysis, confirming the successful isolation of the compounds. Subsequently, the nematicidal activities of the ligand and its complex were assessed through in vitro egg hatching inhibition and mortality rate assays, in comparison to the control, carbofuran (Crf), at concentrations of 50 and 100 µM over a 24–72-h period. The results indicated the ligand's superiority over the complex in both assays at lower concentrations. At a concentration of 50 µM, the ligand HL demonstrated 100% egg-hatching inhibition at 24, 48, and 72 h, whereas the complex CuL2 showed egg-hatching inhibition rates of 93.86 ± 0.22%, 98.76 ± 0.14%, and 99.33 ± 0.52% at the same time intervals. The control, Crf, exhibited inhibition rates of 56.33 ± 0.33%, 69.94 ± 0.6%, and 67.00 ± 0.34% over the same time period. Similarly, at a concentration of 100 µM, both the ligand and complex demonstrated 100% egg-hatching inhibition at 24, 48, and 72 h, while the control showed egg-hatching rates of 88.16 ± 0.84%, 89.9 ± 0.55%, and 90.8 ± 0.50%. Regarding the mortality rate, at 50 and 100 µM, the ligand HL exhibited a 100% mortality rate within 24 to 72 h, whereas the complex CuL2 displayed mortality rates of 56.66 ± 0.33%, 63.3 ± 0.23%, and 86.66 ± 0.13% at 24, 48, and 72 h, respectively, with a mortality rate of 100% at 100 µM within the same time intervals. The control, Crf, demonstrated mortality rates of 54%–67% at 50 µM and 62%–78% at 100 µM within 24–72 h. Additionally, the density-functional theory study revealed the electronic properties of the compounds, reinforcing the experimental findings.