Linkage Isomerism in Silver Acylpyrazolonato Complexes and Correlation with Their Antibacterial Activity

Abstract

Novel silver(I) acylpyrazolonato coordination polymers of formula [Ag(Q(R))]n (1-3) have been synthesized by interaction of silver nitrate with HQ(R) in methanol in the presence of an equivalent quantity of KOH (in general HQ(R) = 1-phenyl-3-methyl-4-RC(═O)-5-pyrazolone, in detail HQ(fb), R = -CF2CF2CF3; HQ(cy), R = -cyclo-C6H11; HQ(be), R = -C(H)═C(CH3)2). [Ag(Q(R))]n react with 2-ethylimidazole (2EtimH), 1-methylimidazole (Meim), and triphenylphosphine (PPh3), affording the mononuclear Ag(Q(fb))(EtimH) (4), Ag(Q(cy))(Meim)2 (5), Ag(Q(be))(Meim) (6), and Ag(Q(R))(PPh3)2 (7-9). All complexes have been analytically and spectroscopically characterized, and for some of them the X-ray crystal structure has been resolved. In particular, the single crystal molecular structure determination of Ag(Q(fb))(EtimH) and Ag(Q(be))(PPh3)2 has confirmed the different coordination modes of the HQ(fb) and HQ(be) acylpyrazolone ligands, the former being bound to the silver(I) ion in a monodentate fashion while the latter in the O2-chelating mode. Density functional theory computations suggest new insights about metal-ligand interactions and the observed linkage isomerism. While phosphine-containing complexes Ag(Q(R))(PPh3)2 (7-9) seem not to be able to efficiently inhibit the growth of Escherichia coli and Staphylococcus aureus, the polynuclear complexes [Ag(Q(R))]n (1-3) and the mononuclear Ag(Q(fb))(EtimH) (4), Ag(Q(cy))(Meim)2 (5), and Ag(Q(be))(Meim) (6) show a high and almost steady in time antibacterial activity, comparable to that of AgNO3. This activity is likely related to the degree of saturation of the silver center and to the presence of different ancillary ligands in the diverse typologies of complexes.

Stability of Antibacterial Silver Carboxylate Complexes against Staphylococcus epidermidis and Their Cytotoxic Effects

“…Silver compounds with anti-inflammatory ligands have recently been synthesized and their stability studied in the solid state with exposure to UV radiation. It has been found that the nature of the ligands, as well as the coordination number and geometry, can influence the stability in the context of exposure to light and temperature variations [ 5 , 7 , 10 , 11 ]. However, the stability of compounds in solution has not been widely studied, nor has the relationship between chemical properties and antibacterial activity over time.…”

Synthesis, spectroscopic characterization, crystal structure, Hirshfeld surface analysis and antimicrobial activities of two triazole Schiff bases and their silver complexes

“…TEM imaging of bacteria exposed to silver nitrate showed phenomenon of DNA condensation, leading to the loss of its replication ability, along with deep structural damage of cell membranes [34]. Also, the antibacterial activity of silver may be due to its binding to the surface of the cell membrane disrupting the permeability and the respiration [69,70].…”

Structure, Antimicrobial Activity, Hirshfeld Analysis, and Docking Studies of Three Silver(I) Complexes-Based Pyridine Ligands

“…Silver-containing compounds continue to attract academic attention for their antimicrobial properties [1][2][3][4][5][6][7][8] but also for the immense variety of its coordination polymers, [9] and sometimes the two coincide [10]. A recent review is optimistic of the future role of silver in medicine, [11] while clinical studies are still not of sufficient quality to judge the practical usefulness of different silver based wound healing materials, the most common medical application [12].…”