Bivalent nickel and zinc complexes of new alkoxy appended L-threonine Schiff base ligand: Synthesis, antileishmanial activity, DNA interaction, photoluminescence and mesomorphic properties

[Display omitted] •Synthesis of L-threonine based Schiff base ligand and its Ni(II) and Zn(II) complexes.•The compounds exhibit potent antileshmanial activity, as well as effective interaction with CT-DNA.•Ligand possess SmA mesomorphism.•Compounds do exhibit photoluminescence property.•Energy optimized geometry of the compounds obtained from DFT study. A new design emissive and smectogenic Schiff base ligand (HL) derived from L-threonine and bivalent nickel and zinc complexes have been synthesized and characterized by different spectral techniques viz., FT-IR, 1H NMR, 13C NMR, UV–visible spectroscopy and elemental analysis. The in vitro screening of the compounds for antiparasitic activity against Leishmania donovani was carried out. Among the compounds, NiL2 was found to exhibit the highest efficacy as a leishmanicidal agent. The in vitro interaction of the compounds with CT-DNA was investigated using absorption, as well as fluorescence spectroscopy. The ligand and complexes are found to possess blue emissive photoluminescence property. The estimated optical band gap of the compounds from UV–visible spectra indicates that the compounds fall within the class of wide-band gap semiconductors. The mesogenic characteristic for all the compounds were studied using polarizing optical microscope (POM) and differential scanning calorimetry (DSC), and it was observed that only the ligand does exhibit smecticA mesophase. The optimized geometry, as well as HOMO-LUMO band gap of the compounds were obtained from Density Functional Theory (DFT) study.