Water-Soluble Silver Coordination Polymers Constructed From Bridging Pyrazine Ligands: Syntheses, X-Ray Structures, Anticancer, and Antimicrobial Investigations

Two novel polymeric complexes were synthesized from the reaction of AgClO₄ with 3-amino-6-(chloromethyl)-2-pyrazinecarbonitrile 4-oxide (L1-Cl) or 3-aminopyrazine-2-carboxylic acid (HL2) to give [Ag(L1-OCH₃)(μ-OClO₃)]_n; (1) or [Ag (HL2)(OClO₃)]_n.nH₂O; (2), respectively. 3-Amino-6-(methoxymethyl)-2-pyrazinecarbonitrile 4-oxide (L1-OCH₃) is formed by the etherification process that occurred during the synthesis of complex 1. The complexes architectures were investigated by single-crystal XRD (SC-XRD). Both complexes have novel and different polymeric forms based on the pyrazine moiety that adopt a bridging mode between the Ag(I) sites with the difference of donor atoms in each complex. The silver(I) centers in the polymeric chain of complex 1 are connected to one another through the bridging pyrazine ligand and perchlorate anions in an alternative manner. In complex 2, HL2 does not only act as a linker between the silver centers but also as a bidentate ligand. Hirshfeld surface analysis demonstrated the importance of H···O contacts in the supramolecular structures of 1 (41.7%) and 2 (30.2%). Biological investigations indicated promising antimicrobial and anticancer properties of these water-soluble complexes. Particularly, complex 1 displays interesting activity against A-549 (IC₅₀ = 10.53 ± 0.44 𝜇M) and MCF-7 (IC₅₀ = 8.41 ± 0.31 𝜇M) cell lines when contrasted to cis-platin. Regarding antibacterial action, the most promising MIC value and inhibition zone diameter are 8 μg/mL and 20 mm, respectively, for 1 against B. subtilis.