Synthesis, biological activities, DFT, and molecular docking of 1,3,4-thiadiazolo[2,3-c]-1,2,4-triazine-Palladium (II) complex

Abstract

Abstract A developed synthesis of 4-amino-6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2 H)-one ( 2 ) was presented. Its reaction with PhNCS in ethanol afforded 3-methyl-7-(phenylamino)-4 H-[1,3,4]thiadiazolo[2,3-c][1,2,4]triazin-4-one (L) via an unexpected mechanism. A combination of different characterization techniques (CHN, IR, NMR, UV-Vis TGA, XRD and MS) was utilized for comprehensive structure elucidation. [Pd(L)Cl 2 ].4DMF complex was obtained by preparing the Pd(II) complex at a molar ratio of 1:1 with respect to Pd(II): L. DFT simulated several proposed intermediates for (L) production. Furthermore, DFT corroborated the square planar geometric configuration of the synthesized Pd(II) complex. In vitro, the antimicrobial activity of the synthesized compound on Escherichia coli , Klebsiella pneumoniae , Staphylococcus aureus , Streptococcus mutans , Candida albicans , and Aspergillus Nigar using the inhibition zone technique was evaluated. Subsequent determination of the minimum inhibitory concentration (MIC) of the Pd complex against Klebsiella confirmed its potent antibacterial activity, in agreement with the pronounced inhibition zone observed in the diffusion assay. The results indicate that the palladium (II) complex is more potent than the ligand against the tested microorganisms, especially against K. pneumoniae , where it demonstrated promising activity that, upon further research, could be used to overcome gentamicin resistance. Both compounds exhibited similar cytotoxicity against the proliferation of the human liver cancer cell line. The interactions at the docking active sites were assessed using the chosen proteins, EGFR tyrosine kinase, and the protein crystal structure of GlcN-O-P synthase. The anti-inflammatory effect results indicated that both compounds have a moderate effect on bovine serum albumin (BSA).