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Two zinc(II) complexes with dimethyl 2,2′-bipyridine-4,5-dicarboxylate (py-2py) of the general formula [Zn(py-2py)X2], X = Cl− (1) and Br− (2) were synthesized and characterized by NMR, IR and UV-Vis spectroscopy and single-crystal X-ray diffraction analysis. Complexes 1 and 2 are isostructural and adopt a slightly distorted tetrahedral geometry with values of tetrahedral indices τ4 and τ'4 in the range of 0.80–0.85. The complexes were evaluated for their in vitro antimicrobial activity against two bacterial (Pseudomonas aeruginosa and Staphylococcus aureus) and two fungal strains (Candida albicans and Candida parapsilosis), while their cytotoxicity was tested on the normal human lung fibroblast cell line (MRC-5) and the model organism Caenorhabditis elegans. Complex 1 showed moderate activity against both Candida strains. However, this complex was twofold more cytotoxic compared to complex 2. The complexes tested had no effect on the survival rate of C. elegans. Complex 2 showed the ability to inhibit filamentation of C. albicans, while complex 1 was more effective than complex 2 in inhibiting biofilm formation. The interactions of complexes 1 and 2 with calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) were studied to evaluate their binding affinity toward these biomolecules. [ABSTRACT FROM AUTHOR]

Mononuclear silver(I) complexes with 1,7-phenanthroline (1,7-phen), [Ag(NO 3 - O,O′ ) (1,7-phen- N7 ) 2 ] ( 1 ) and [Ag(1,7-phen- N7 ) 2 ]X, X = ClO 4 − ( 2 ), CF 3 SO 3 − ( 3 ), BF 4 − ( 4 ) and SbF 6 − ( 5 ) were synthesized and structurally characterized by NMR ( 1 H and 13 C), IR and UV–Vis spectroscopy and ESI mass spectrometry. The crystal structures of 1, 3 and 4 were determined by single-crystal X-ray diffraction analysis. In all these complexes, 1,7-phen coordinates to the Ag(I) ion in a monodentate fashion via the less sterically hindered N7 nitrogen atom. The investigation of the solution stability of 1 – 5 in DMSO revealed that they are sufficiently stable in this solvent at room temperature. Complexes 1 – 5 showed selectivity towards Candida spp. in comparison to bacteria, effectively inhibiting the growth of four different Candida species with minimal inhibitory concentrations (MIC) between 1.2 and 11.3 μM. Based on the lowest MIC values and the lowest cytotoxicity against healthy human fibroblasts with selectivity index of more than 30, the antifungal potential was examined in detail for the complex 1 . It had the ability to attenuate C. albicans virulence and to reduce epithelial cell damage in the cell infection model. Induction of reactive oxygen species (ROS) response has been detected in C. albicans , with fungal DNA being one of the possible target biomolecules. The toxicity profile of 1 in the zebrafish model ( Danio rerio ) revealed improved safety and activity in comparison to that of clinically utilized silver(I) sulfadiazine. [ABSTRACT FROM AUTHOR]

New polynuclear silver(I) complexes with 1,5-naphthyridine (1,5-naph), [Ag(NO 3)(1,5-naph)] n (Ag1), [Ag(CF 3 COO)(1,5-naph)] n (Ag2) and [Ag(CF 3 SO 3)(1,5-naph)] n (Ag3) were synthesized by the reaction of the corresponding silver(I) salt and 1,5-naph in ethanol at room temperature. These complexes were characterized by NMR, IR and UV–Vis spectroscopy, while their crystal structures were determined by single-crystal X-ray diffraction analysis. In all these complexes, 1,5-naph acts as a bridging ligand between two Ag(I) ions, while the remaining coordination sites are occupied by oxygen atom(s) of the corresponding anion. The antimicrobial efficiency of these silver(I) complexes was evaluated against the broad panel of Gram-positive and Gram-negative bacteria and fungi. The complexes showed good to moderate antibacterial activity with the minimal inhibitory concentration (MIC) values being in the range 2.5–100 μg/mL (6.5–333.3 μM), while their antifungal activity against the investigated Candida spp. was significantly higher (MIC = 0.78–6.25 μg/mL; 2.6–20.8 μM). Moreover, complexes Ag1 and Ag2 effectively inhibited C. albicans biofilms formation, while Ag1 was also shown to inhibit the formation of mixed C. albicans / Pseudomonas aeruginosa biofilms. Toxicological evaluations on zebrafish (Danio rerio) embryos revealed that all silver(I) complexes could be applied as antifungal agents, whereas Ag3 had the best therapeutic potential showing both the lowest MIC values against the tested Candida strains and the non-toxic in vivo response in the zebrafish embryos at these doses. Silver(I) complexes with 1,5-naphthyridine have shown significant and selective anti- Candida activity, being less toxic in vivo in zebrafish embryos than the clinically used silver(I) sulfadiazine. Unlabelled Image • Three silver(I) complexes with 1,5-naphthyridine were synthesized and characterized. • Silver(I) complexes showed significant and selective anti- Candida activity. • Silver(I) complexes inhibited Candida albicans biofilms formation. • Silver(I) complexes are less toxic in vivo than silver(I) sulfadiazine. [ABSTRACT FROM AUTHOR]

Three diamines, 1,3-propanediamine (1,3-pd), 2,2-dimethyl-1,3-propanediamine (2,2-diMe-1,3-pd) and (±)-1,3-pentanediamine (1,3-pnd), were used for the synthesis of nickel(II) complexes 1-3, respectively, of the general formula [Ni(L)2(H2O)2]Cl2. The stoichiometries of the complexes were confirmed by elemental microanalysis and their structures were elucidated by spectroscopic (UV-Vis and IR) and molar conductivity measurements. The complexes 1-3, along with NiCl26H2O and the diamine ligands, were evaluated against a panel of microbial strains that are associated with skin, wound, urinary tract and nosocomial infections. The obtained results revealed no significant activity of 1-3 against the investigated bacterial strains. On the other hand, they showed good antifungal activity against pathogenic Candida strains, with minimum inhibitory concentration (MIC) values in the range from 15.6 to 62.5 ±g mL-1. The best anti-Candida activity was observed for complex 2 against C. parapsilosis, while the least susceptible to the effect of the complexes was C. krusei. The antiproliferative effect on normal human lung fibroblast cell line MRC-5 was also evaluated in order to determine the therapeutic potential of nickel(II) complexes 1-3. These complexes showed lower negative effects on the viability of the MRC-5 cell line than the clinically used nystatin and comparable selectivity indexes to that of this antifungal drug. [ABSTRACT FROM AUTHOR]

• Two silver(I) complexes with econazole were synthesized and characterized. • DFT was used for investigation of solution behaviour of the complexes. • Silver(I) complexes showed significant activity against the tested Candida species. • Silver(I) complexes reduced the amount of ergosterol in the fungal cell membrane. • Silver(I) complexes showed remarkable activity against the Staphylococcus aureus. Two new silver(I) complexes with the antifungal agent econazole (ecz) of the general formula [Ag(еcz) 2 ]X, X = CF 3 SO 3 − (Ag1) and PF 6 − (Ag2), were synthesized and structurally characterized by spectroscopic (1H NMR, IR and UV–Vis) and electrochemical methods. The crystal structure of Ag2 was determined by single crystal X-ray diffraction analysis, confirming an ideal linear geometry of the silver(I) ion in this complex. In addition, by utilising Hirshfeld surface analysis (HSA), it was verified that the crystal structure of Ag2 is stabilized by H⋯H, H⋯Cl, C⋯H, and H⋯F interactions. Density functional theory (DFT) calculations provided additional evidence for formation of the complexes in the solid state and their stability in solution. The coordination of ecz to the silver(I) ion endowed this agent with antibacterial activity against Gram-positive (Pseudomonas aeruginosa and Escherichia coli) and Gram-negative (Staphylococcus aureus and Listeria monocytogenes) bacteria. The most significant antibacterial activity of Ag1 and Ag2 was observed against S. aureus with 56- and 73-fold improvement, respectively, compared to the parent drug. Moreover, a study of the bacterial antibiofilm activity revealed that these complexes were able to prevent approximately 90 % of biofilm formation at their low concentrations. Also, both complexes have shown more pronounced anti- Candida activity than econazole itself, being less toxic on the human normal fibroblast cell line MRC-5. The total amount of ergosterol was reduced in the presence of the subinhibitory concentrations of Ag1 and Ag2 complexes, which was also confirmed by a molecular docking study with two isomers of cytochrome P450 sterol 14 α -demethylase, CYP51B and CYP130, as target receptors. Two silver(I) complexes with clinically used antifungal agent econazole have shown significantly improved anti- Staphylococcus and anti- Candida activities in comparison to organic-based drug itself, being less toxic on the human normal fibroblast cell line MRC-5. [Display omitted] [ABSTRACT FROM AUTHOR]

The introduction of an epoxide function in the frame of 1,10-phenanthroline ligand has a significant influence on the corresponding silver(I) complex structure and its antimicrobial and antiproliferative activities. • Silver(I) complexes with 1,10-phenanthroline-based ligands were synthesized. • The ligand structure had an influence on the complex nuclearity and geometry. • Silver(I) complexes showed significant and selective anti- Candida activity. • An epoxide function in the frame of 1,10-phenanthroline increased cytotoxicity. • Silver(I) complexes did not cause DNA degradation. In a continuing search for a novel metal-containing antimicrobial agents, the present study reports the synthesis, characterization and biological evaluation of two silver(I) complexes with 1,10-phenanthroline-based ligands, [Ag(1,10-phen) 2 ]CF 3 COO·H 2 O (Ag1) and [Ag(CF 3 COO)(5,6-epoxy-1,10-phen)] 2 (Ag2), 1,10-phen is 1,10-phenanthroline and 5,6-epoxy-1,10-phen is 5,6-epoxy-5,6-dihydro-1,10-phenanthroline. The complexes were characterized by different spectroscopic techniques (IR, 1H and 13C NMR and UV–Vis), while the crystal structure of Ag2 complex was determined by a single-crystal X-ray diffraction analysis. The spectroscopic data confirmed that the structure of Ag1 complex, with silver(I) ion tetrahedrally coordinated by two bidentate 1,10-phen ligands, is in accordance to the previous report (S.E. Paramonov et al., 2003). The crystallographic results showed that in dinuclear Ag2 complex, both Ag(I) ions are coordinated bidentately by 5,6-epoxy-1,10-phen and monodentately by trifluoroacetate, with presence of the short Ag∙∙∙Ag contact of 2.963 Å. Both silver(I) complexes were evaluated in vitro for antimicrobial activity against four bacterial and four Candida species, showing selectivity towards the investigated species of Candida with minimal inhibitory concentrations (MICs) between 0.9 and 12.5 µM. Moreover, Ag2 complex manifested significant antiproliferative properties in the case of a range of human cell lines, including human breast cancer (MDA-MB 231), which resulted from the presence of epoxy functional group in the ligand. The gel electrophoresis results obtained from the studies of Ag1 and Ag2 interactions with bacteriophage lambda DNA (λDNA) suggested that these complexes did not cause DNA degradation. [ABSTRACT FROM AUTHOR]

This study shows how the nature of the metal ion reflects on antimicrobial properties and interaction of {[Ag(1,6-naph)(H 2 O)](BF 4)} n (1) and [AuCl 3 (1,6-naph)] (2) with biomolecules. [Display omitted] In the present study, synthesis of silver(I) and gold(III) coordination compounds with 1,6-naphthyridine (1,6-naph), {[Ag(1,6-naph)(H 2 O)](BF 4)} n (1) and [AuCl 3 (1,6-naph)] (2), was reported. The methods used for the structural characterization of a new compound 1 included IR, NMR (1H and 13C) and UV–Vis spectroscopy, cyclic voltammetry and single-crystal X-ray diffraction analysis. The crystallographic results showed that compound 1 represents silver(I) coordination polymer, in which 1,6-naph ligand acts as a bidentate bridging ligand connecting two Ag(I) ions via its N1 and N6 nitrogen atoms, while the third coordination site of the metal ion is occupied by the water oxygen atom, resulted in a T -shape geometry. Compounds 1 and 2 were evaluated in vitro for antimicrobial activity against five bacterial and two Candida species, while their cytotoxicity was tested on the normal human lung fibroblast cell line (MRC-5). Compound 1 has manifested a remarkable antifungal activity on both tested Candida strains (C. albicans and C. parapsilosis) with minimal inhibitory concentrations (MICs) of 1.43 and 11.38 µM (0.49 and 3.9 µg/mL), respectively, while no significant antimicrobial activity was observed for 2. Moreover, silver(I) coordination polymer 1 inhibits the hyphae formation of C. albicans at subinhibitory concentration. The binding affinity of both compounds 1 and 2 with calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) was studied by fluorescence spectroscopy, indicating their ability to interact with these biomolecules, with compound 2 being more reactive. [ABSTRACT FROM AUTHOR]

Graphical abstract 1-Benzyl-1 H -tetrazoles were used as ligands for the synthesis of silver(I) complexes which have shown remarkable antimicrobial activity against the different fungal and bacterial strains and good therapeutic potential. Abstract Herein, we report the synthesis and structural characteristics of three tetrazole-containing compounds, 1-benzyl-1 H -tetrazole (bntz), 1-benzyl-1 H -tetrazol-5-amine (bntza) and 1-(4-methoxybenzyl)-1 H -tetrazol-5-amine (mbntza) and the corresponding silver(I) complexes of the general formula [Ag(NO 3 - O)(L- N4) 2 ] n , L = bntz (1), bntza (2) and mbntza (3). Silver(I) complexes 1 – 3 and 1-benzyl-1 H -tetrazoles have been studied in detail by NMR, IR and UV–Vis spectroscopic methods and the structures of 1 and 2 have been determined by single-crystal X-ray diffraction analysis. The results of these analyses revealed a monodentate coordination of the ligands to Ag(I) ion via the N4 tetrazole nitrogen. The antimicrobial potential of silver(I) complexes 1 – 3 was evaluated against the broad panel of Gram-positive and Gram-negative bacteria and fungi, displaying their remarkable inhibiting activity with MIC (minimal inhibitory concentration) values in the range 2–8 and 0.16–1.25 μg/mL (3.8–16.3 and 0.31–2.15 μM), respectively. On the other hand, 1-benzyl-1 H -tetrazoles used for the synthesis of the silver(I) complexes were not active against the investigated strains, suggesting that the activity of the complexes originates from the Ag(I) ion exclusively. Moreover, silver(I) complexes 1 – 3 have good therapeutic potential, which can be deduced from their moderate cytotoxicity on the human fibroblast cell line MRC5, with IC 50 values falling in the range 30–60 μg/mL (57.7–103.4 μM). [ABSTRACT FROM AUTHOR]