Synthesis, characterizations, antitumor and antimicrobial evaluations of novel Mn(II) and Cu(II) complexes with NNN-tridentate s-Triazine-Schiff base ligand

The new s-triazine hydrazone, 2,4-bis(morpholin-4-yl)-6-[(E)-2-[1-(pyridin-2-yl)ethylidene]hydrazin-1-yl]-1,3,5-triazine, (L) ligand was used to synthesize three new metal complexes. Single-crystal X-ray diffraction analysis indicated that the [MnLCl₂] (1) and [CuLCl₂].H₂O (2) complexes exhibit distorted trigonal bipyramidal coordination geometry with one NNN-tridentate ligand L and two chloride ions. The trigonality index (τ₅) was calculated to be 0.332 and 0.235 Ǻ for complexes 1 and 2, respectively. In case of the [CuL(NO₃)₂] complex (3), the Cu(II) ion is hexa-coordinated with one NNN-tridentate ligand L, one bidentate nitrate and one monodentate nitrate. The supramolecular structure of complexes 1 and 3 was analyzed using Hirshfeld calculations; hydrogen bonding-based interactions have the largest contribution in their molecular packing. The anticancer and antimicrobial activities of the ligand and its complexes (1–3) were examined. The three complexes have higher anticancer activity against colon HCT-116 and lung A-549 cancer cell lines than the free ligand (L). The only exception is complex 1 which has less cytotoxic activity against lung A-549 cancer cell line than L. Interestingly, the Cu(II) complexes have higher cytotoxic activity than the Mn(II) complex, where complex 3 has the best anticancer activity against HCT-116 (IC₅₀ = 7.78 ± 0.27 μg/mL) and A-549 (12.40 ± 0.54 μg/mL) cell lines. In addition, the three complexes showed greater activity against gram-positive bacteria (S. aureus and B. subtilis) than gram-negative bacteria (E. coli and P. vulgaris) where 3 has best antibacterial activity.