Monomeric Zn(II) and 3D polymeric Ag(I) complexes with a cationic s-triazine hydrazone-based ligand; synthesis, structure, coordination behavior and biological studies.

The novel (E)-6-(2-(1-(pyridin-4-yl)ethylidene)hydrazineyl)-1,3,5-triazine-2,4-diamine (L) was used to synthesize the monomeric [Zn(HL)Cl3] (1) and the 3D polymeric [Ag4(HL)2(NO3)6]n (2) complexes. Their structures were verified through single-crystal X-ray diffraction. In both complexes, L is found protonated leading to the cationic coordinating ligand (HL+). 1 exhibits a slightly distorted tetrahedral geometry (τ4 = 0.93 and τ4'=0.92) while 2 contains four crystallographically non-equivalent Ag(I) ions. Ag1 has a square pyramidal geometry (τ5 = 0.23), Ag2 exhibits a distorted tetrahedron (τ4 = 0.55 and τ4'=0.54), Ag3 and Ag4 possess a distorted trigonal planar geometry. Hirshfeld surface analysis reveals that hydrogen-based interactions primarily dictate the molecular packing of complexes 1 and 2 (81.3% and 69.2%, respectively). Theoretical NBO analysis was conducted to quantify the flux of electrons from the donor to the acceptor and evaluate the orbital-orbital interactions of the coordinate bonds in both complexes. Regarding to cytotoxicity, 2 achieved impressive results with IC50 values of 9.96 ± 0.35 and 15.84 ± 0.46 µM against HepG-2 and MCF-7 cell lines, respectively, surpassing cis-platin by six and four times, respectively. Additionally, 2 exhibits broad-spectrum antimicrobial activity, achieving the most significant activity against B. subtilis, with a diameter of inhibition zone of 27 mm and MIC value of 3.71 µM, comparable to that of gentamicin as a positive control.