N-heterocyclic-carbene vs diphosphine auxiliary ligands in thioamidato Cu(I) and Ag(I) complexes towards the development of potent and dual-activity antibacterial and apoptosis-inducing anticancer agents

Group 11 metal complexes exhibit promising antibacterial and anticancer properties which can be further enhanced by appropriate ligands. Herein, a series of mononuclear thioamidato Cu(I) and Ag(I) complexes bearing either a diphosphine (P^P) or a N-heterocyclic carbene (NHC) auxiliary ligand (L) was synthesized, and the impact of the co-ligand L on the in vitro antibacterial and anticancer properties of their complexes was assessed. All complexes effectively inhibited the growth of various bacterial strains, with the NHC-Cu(I) complex found to be particularly effective against the Gram (+) bacteria (IC50 = 1-4 μg mL-1). Cytotoxicity studies against various human cancer cells revealed their high anticancer potency and the superior activity of the NHC-Ag(I) complex (IC50 = 0.95-4.5 μΜ). Flow cytometric analysis on lung and breast cancer cells treated with the NHC-Ag(I) complex suggested an apoptotic cell-death pathway; molecular docking calculations provided mechanistic insights, proving the capacity of the complex to bind on apoptosis-regulating proteins and affect their functionalities.

Synergy of redox-activity and hemilability in thioamidato cobalt(III) complexes for the chemoselective reduction of nitroarenes to anilines: catalytic and mechanistic investigation

Reduction of nitro-compounds to amines is one of the most often employed and challenging catalytic processes in the fine and bulk chemical industry. Herein, we present two series of mononuclear homoleptic and heteroleptic Co(III) complexes, i.e., [Co(LNS)3] and [Co(LNS)2L1L2]x+, respectively (x = 0 or 1, LNS = pyrimidine- or pyridine-thioamidato, L1/L2 = thioamidato, phosphine or pyridine), which successfully catalyze the transformation of nitroarenes to anilines by methylhydrazine. The catalytic reaction can be accomplished for a range of electronically and sterically diverse nitroarenes, using mild experimental conditions and low catalyst loadings, resulting in the corresponding anilines in high yields, with high chemoselectivity, and no side-products. Electronic and steric properties of the ligands play pivotal role in the catalytic efficacy of the respective complexes. In particular, complexes bearing ligands of high hemilability/lability and being capable of stabilizing lower metal oxidation-states exhibit the highest catalytic activity. Mechanistic investigations suggest the participation of the Co(III) complexes in two parallel reaction pathways: (a) coordination-induced activation of methylhydrazine and (b) reduction of nitroarenes to anilines by methylhydrazine, through the formation of Co(I) and Co-hydride intermediates.

Neutral and cationic nickel(II) complexes with substituted salicylaldehydes: Characterization, antibacterial activity, and interaction with biomacromolecules

Four neutral and six cationic nickel(II) complexes of the substituted salicylaldehydes (X-diCl-saloH), namely 3,5-dichloro-salicylaldehyde (3,5-diCl-saloH) and 5-fluoro-salicylaldehyde (5-F-saloH), were synthesized in the absence or presence of the N,N'-donors 1,10-phenanthroline (phen), 2,9-dimethyl-1,10-phenanthroline (neoc), or 2,2'-bipyridylamine (bipyam) as co-ligands and were characterized by various techniques. The obtained complexes bear the general formulas [Ni(X-salo)2(H2O)2], [Ni(3,5-diCl-salo)2(neoc/phen)] and [Ni(X-salo)(N,N'-donor)2](PF6). The crystal structures of three complexes were determined by single-crystal X-ray crystallography revealing a bidentate coordination of the salicylaldehydes. The interaction of the compounds with calf-thymus DNA was studied by diverse techniques which revealed an intercalative interaction for the neutral complexes [Ni(X-salo)2(H2O)2] and [Ni(3,5-diCl-salo)2(neoc/phen)]and the co-existence of electrostatic interactions for the cationic complexes [Ni(X-salo)(N,N'-donor)2](PF6). The compounds bind tightly and reversibly to serum albumins. The antibacterial activity of the compounds was investigated against Staphylococcus aureus ATCC 6538, Bacillus subtilis ATCC 6633, Escherichia coli NCTC 29,212 and Xanthomonas campestris ATCC 1395 and the complexes bearing neoc as co-ligand proved the most potent.

Erbium(III) coordination compounds with substituted salicylaldehydes: Characterization and biological profile

Five erbium(III) complexes with salicylaldehyde (saloH for 1), and mono- (5-X-saloH; X = NO₂ and Me for 2 and 3, respectively) or di-substituted salicylaldehydes (3,5-diX-saloH; X = Cl and Br for 4 and 5, respectively) were synthesized and characterized by physicochemical and spectroscopic techniques and single-crystal X-ray crystallography. All five complexes have the general formula [Er(deprotonated salicylaldehyde)₃(MeOH)(H₂O)]. The structure of complexes [Er(3,5-diCl-salo)₃(MeOH)(H₂O)]·1.5MeOH (complex 4) and [Er(3,5-diBr-salo)₃(MeOH)(H₂O)]·1.75MeOH (complex 5) were verified by single-crystal X-ray crystallography. The evaluation of antioxidant activity of the complexes was focused on their ability to scavenge 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) free radicals and to reduce H₂O₂. The interaction of the complexes with calf-thymus DNA was investigated by UV-vis spectroscopy, viscosity measurements and via competitive studies with ethidium bromide in order to evaluate the possible DNA-binding mode and to determine the corresponding DNA-binding constants. The affinity of the complexes for bovine and human serum albumins was explored by fluorescence emission spectroscopy and the corresponding binding constants were determined.

Possible implementation of salicylate anions in lead detoxification

The water-soluble coordination polymer of formula {[Pb(Sal)₂(H₂O)]_n} (SaLead), was obtained from the reaction between Pb(NO₃)₂ and the potassium salt of salicylic acid (SalH), an anti-inflammatory drug, which is also use as food preservation, in cosmetics etc. The compound was characterized by melting point, Attenuated Total Reflectance-Fourier Transform Infra-Red (ATR-FTIR) spectroscopy and X-ray diffraction crystallography (XRD) in solid state and in solution by Ultra Violet (UV) and ¹H NMR spectroscopies. The binding affinity of SalK to Pb(II) ions towards SaLead was determined in order to examine its possible implementation in lead detoxification. The in vitro non-toxic behaviour of SalK and its complex SaLead was evaluated against normal human fetal lung fibroblast cells (MRC-5). The corresponding IC₅₀ values are 260 ± 13 and > 1600 μM respectively. The non-genotoxic in vitro activity of SaLead was confirmed with the micronucleus (MN) assay, while its in vivo non-toxicity behaviour was evaluated with Allium cepa and Artemia salina assays.

Iron(III) Complexes with Non-Steroidal Anti-Inflammatory Drugs: Structure, Antioxidant and Anticholinergic Activity, and Interaction with Biomolecules

One the main research goals of bioinorganic chemists is the synthesis of novel coordination compounds possessing biological potency. Within this context, three novel iron(III) complexes with the non-steroidal anti-inflammatory drugs diflunisal and diclofenac in the presence or absence of the nitrogen donors 1,10-phenanthroline or pyridine were isolated and characterized by diverse techniques. The complexes were evaluated for their ability to scavenge in vitro free radicals such as hydroxyl, 1,1-diphenyl-2-picrylhydrazyl and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radicals, revealing their selective potency towards hydroxyl radicals. The in vitro inhibitory activity of the complexes towards the enzymes acetylcholinesterase and butyrylcholinesterase was evaluated, and their potential to achieve neuroprotection appeared promising. The interaction of the complexes with calf-thymus DNA was examined in vitro, revealing their ability to intercalate in-between DNA nucleobases. The affinity of the complexes for serum albumins was evaluated in vitro and revealed their tight and reversible binding.

New Apoptosis Inducers Containing Anti-inflammatory Drugs and Pnictogen Derivatives: A New Strategy in the Development of Mitochondrial Targeting Chemotherapeutics

{[Ag₈(Mef)₈(μ₂-S,O-DMSO)₂(μ₂-O-DMSO)₂(O-DMSO)₈]·2(H₂O)} (1), [Ag(Mef)(tpP)₂] (2), [Ag(Mef)(tpAs)₃] (3), and {2 [Ag(Mef)(tpSb)₃] (DMSO)} (4) were obtained by the conjugation of mefenamic acid (MefH), a nonsteroidal anti-inflammatory drug (NSAID), with a mitochondriotropic derivative of pnictogen tpE (tp = triphenyl group; E = P, As, and Sb) through silver(I). Their hydrophilicity was adjusted by their dispersion into sodium lauryl sulfate (SLS), forming SLS@1-4. 1-4 and SLS@1-4 were characterized by their spectral data and X-ray crystallography. They inhibit the proliferation of human breast adenocarcinoma cells MCF-7 (hormone-dependent (HD)) and MDA-MB-231 (hormone-independent (HI)). X-ray fluorescence reveals the Ag cellular uptake. The in vitro and in vivo nongenotoxicity was confirmed with micronucleus (MN), Artemia salina, and Allium cepa assays. Their mechanism of action was studied by cell morphology, DNA fragmentation, acridine orange/ethidium bromide (AO/EB) staining, cell cycle arrest, mitochondrial membrane permeabilization tests, DNA binding affinity, and LOX inhibitory activity and was rationalized by regression analysis.

Transition metal(II) complexes with the non–steroidal anti–inflammatory drug oxaprozin: Characterization and biological profile

A series of copper(II), nickel(II) and cobalt(II) complexes with the non-steroidal anti-inflammatory drug oxaprozin (Hoxa) have been synthesized and characterized by diverse techniques. The crystal structures of two copper(II) complexes, namely the dinuclear complex [Cu₂(oxa)₄(DMF)₂] (1) and the polymeric complex {[Cu₂(oxa)₄]·2MeOH·0.5MeOH}₂ (12) were determined by single-crystal X-ray diffraction studies. In order to evaluate in vitro the antioxidant activity of the resultant complexes, their scavenging ability towards 1,1-diphenyl-picrylhydrazyl (DPPH), hydroxyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals was investigated revealing their high effectiveness against these radicals. The binding of the complexes to bovine serum albumin and human serum albumin was examined and the corresponding determined albumin-binding constants showed a tight and reversible interaction. The interaction of the complexes with calf-thymus DNA was monitored by diverse techniques including UV-vis spectroscopy, cyclic voltammetry, DNA-viscosity measurements and competitive studies with ethidium bromide. Intercalation may be proposed as the most possible DNA-interaction mode of the complexes.

Copper(II) complexes with 3,5-dihalogeno-salicylaldehydes: Synthesis, structure and interaction with DNA and albumins

Eight copper(II) complexes of 3,5-dichloro-salicyladehyde or 3,5-dibromo-salicyladehyde (3,5-diX-saloH, X = Br or Cl) were synthesized in the absence or presence of a N,N'-donor co-ligand such as 2,2'-bipyridylamine, 1,10-phenanthroline, or 2,2'-bipyridine. The resultant compounds were formulated as [Cu(3,5-diX-salo)₂(MeOH)₂] (1-2) and [Cu(3,5-diX-salo)(N,N'-donor)Cl] (3-8) and were characterized by diverse techniques. The crystal structures of three complexes were determined by single-crystal X-ray crystallography. Diverse techniques were employed in order to investigate the interaction of the complexes with calf-thymus DNA which showed intercalation as the most possible mode of their interaction. The affinity of the complexes for bovine serum albumin and human serum albumin was evaluated by fluorescence emission spectroscopy in order to calculate the binding constants which suggested a tight and reversible binding. SYNOPSIS: A series of copper(II) complexes with 3,5-dihalogen-substituted salicylaldehydes as ligands were isolated and characterized. In vitro biological studies showed the intercalation of the compounds with calf-thymus DNA and their tight and reversible binding with serum albumins.

Inhibition of Cancer Cell Proliferation and Bacterial Growth by Silver(I) Complexes Bearing a CH3-Substituted Thiadiazole-Based Thioamide

Ag(I) coordination compounds have recently attracted much attention as antiproliferative and antibacterial agents against a wide range of cancer cell lines and pathogens. The bioactivity potential of these complexes depends on their structural characteristics and the nature of their ligands. Herein, we present a series of four Ag(I) coordination compounds bearing as ligands the CH₃-substituted thiadiazole-based thioamide 5-methyl-1,3,4-thiadiazole-2-thiol (mtdztH) and phosphines, i.e., [AgCl(mtdztH)(PPh₃)₂] (1), [Ag(mtdzt)(PPh₃)₃] (2), [AgCl(mtdztH)(xantphos)] (3), and [AgmtdztH)(dppe)(NO₃)]_n (4), where xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene and dppe = 1,2-bis(diphenylphosphino)ethane, and the assessment of their in vitro antibacterial and anti-cancer efficiency. Among them, diphosphine-containing compounds 3 and 4 were found to exhibit broad-spectrum antibacterial activity characteristics against both Gram-(+) and Gram-(-) bacterial strains, showing high in vitro bioactivity with IC₅₀ values as low as 4.6 μΜ. In vitro cytotoxicity studies against human ovarian, pancreatic, lung, and prostate cancer cell lines revealed the strong cytotoxic potential of 2 and 4, with IC₅₀ values in the range of 3.1-24.0 μΜ, while 3 and 4 maintained the normal fibroblast cells' viability at relatively higher levels. Assessment of these results, in combination with those obtained for analogous Ag(I) complexes bearing similar heterocyclic thioamides, suggest the pivotal role of the substituent groups of the thioamide heterocyclic ring in the antibacterial and anti-cancer efficacy of the respective Ag(I) complexes. Compounds 1-4 exhibited moderate in vitro antioxidant capacity for free radicals scavenging, as well as reasonably strong ability to interact with calf-thymus DNA, suggesting the likely implication of these properties in their bioactivity mechanisms. Complementary insights into the possible mechanism of their anti-cancer activity were provided by molecular docking calculations, exploring their ability to bind to the overexpressed fibroblast growth factor receptor 1 (FGFR1), affecting cancer cells' functionalities.

Copper(II) Complexes of 5-Fluoro-Salicylaldehyde: Synthesis, Characterization, Antioxidant Properties, Interaction with DNA and Serum Albumins

The synthesis, characterization and biological profile (antioxidant capacity, interaction with calf-thymus DNA and serum albumins) of five neutral copper(II) complexes of 5-fluoro-salicylaldehyde in the absence or presence of the N,N'-donor co-ligands 2,2'-bipyridylamine, 2,9-dimethyl-1,10-phenanthroline, 1,10-phenanthroline and 2,2'-bipyridine are presented herein. The compounds were characterized by physicochemical and spectroscopic techniques. The crystal structures of four complexes were determined by single-crystal X-ray crystallography. The ability of the complexes to scavenge 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radicals and to reduce H₂O₂ was investigated in order to evaluate their antioxidant activity. The interaction of the compounds with calf-thymus DNA possibly takes place via intercalation as suggested by UV-vis spectroscopy and DNA-viscosity titration studies and via competitive studies with ethidium bromide. The affinity of the complexes with bovine and human serum albumins was examined by fluorescence emission spectroscopy revealing the tight and reversible binding of the complexes with the albumins.

Manganese(II) complexes with 5-nitro-2-hydroxy-benzaldehyde or substituted 2-hydroxy-phenones: Structure and interaction with bovine serum albumin and calf-thymus DNA

A series of Mn(II) complexes of 5-nitro-salicyladehyde or substituted 2-hydroxy-phenones (HL) were synthesized in the absence or presence of a N,N'-donor co-ligand such as 2,2'-bipyridine, 1,10-phenanthroline, or 2,2'-bipyridylamine. The resultant coordination compounds were formulated as [Mn(L)₂(CH₃OH)₂] (1-3) and [Mn(L)₂(N,N'-donor)] (4-14), respectively, and characterized by diverse techniques. The crystal structures of three complexes were determined by single-crystal X-ray crystallography. Diverse techniques were employed to study the interaction of the complexes with calf-thymus DNA and showed intercalation as the most possible mode of their tight interaction. The affinity of the complexes for bovine serum albumin was investigated by fluorescence emission spectroscopy in order to calculate the binding constants which suggested a tight and reversible binding.

Silver(I) complexes bearing heterocyclic thioamide ligands with NH2 and CF3 substituents: effect of ligand group substitution on antibacterial and anticancer properties

In recent years, there has been an increasing interest in the study of Ag(I) coordination compounds as potent antibacterial and anticancer agents. Herein, a series of Ag(I) complexes bearing phosphines and heterocyclic thioamide ligands with highly electronegative NH₂- and CF₃-group substituents, i.e. [AgCl(atdztH)(xantphos)] (1), [Ag(μ-atdztH)(DPEphos)]₂(NO₃)₂ (2), [Ag(atdzt)(PPh₃)₃] (3), [Ag(μ-atdzt)(DPEphos)]₂ (4), and [Ag(μ-mtft)(DPEphos)]₂ (5), where atdztH = 5-amino-1,3,4-thiadiazole-2-thiol, mtftH = 4-methyl-5-(trifluoromethyl)-1,2,4-triazol-3-thiol, xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene, and DPEphos = bis(2-diphenylphosphino-phenyl)ether, were synthesized, and their in vitro antibacterial and anticancer properties were evaluated. Complexes 1-4 bearing the NH₂-substituted thioamide exhibited moderate-to-high activity against S. aureus, B. subtilis, B. cereus and E. coli bacterial strains. A high antiproliferative activity was also observed for 1-3 against SKOV-3, Hup-T3, DMS114 and PC3 cancer cell lines (IC₅₀ = 4.0-11.7 μM), as well as some degree of selectivity against MRC-5 normal cells. Interestingly, 5 bearing the CF₃-substituted thioamide is completely inactive in all bioactivity studies. Binding of 1-3 to drug-carrier proteins BSA and HSA is reasonably strong for their uptake and subsequent release to possible target sites. The three complexes show a significant in vitro antioxidant ability for scavenging free radicals, suggesting likely implication of this property in the mechanism of their bioactivity, but a low potential to destroy the double-strand structure of CT-DNA by intercalation. Complementary insights into possible bioactivity mechanisms were provided by molecular docking calculations, exploring the ability of complexes to bind to bacterial DNA gyrase, and to the overexpressed in the aforementioned cancer cells Fibroblast Growth Factor Receptor 1, affecting their functionalities.

Detection and Sorption of Heavy Metal Ions in Aqueous Media by a Fluorescent Zr(IV) Metal-Organic Framework Functionalized with 2-Picolylamine Receptor Groups

Increasing global environmental pollution due to heavy metal ions raises the importance of research on new multifunctional materials for simultaneous detection and removal of these contaminants from water resources. In this study, we report a microporous 8-connected Zr⁴⁺ metal-organic framework (MOF) based on a terephthalate ligand decorated with a chelating 2-picolylamine side group (dMOR-2), which shows highly efficient fluorescence sensing and sorption of heavy metal cations. We demonstrate by detailed fluorescence studies the ability of a water-dispersible composite of dMOR-2 with polyvinylpyrrolidone for real-time detection of Cu²⁺, Pb²⁺, and Hg²⁺ in aqueous media. The limits of detection were found to be below 2 ppb for these species, while the system's performance is not affected by the presence of other potentially competitive ions. In addition, sorption studies showed that a composite of dMOR-2 with calcium alginate (dMOR-2@CaA) is an excellent sorbent for Pb²⁺ and Cu²⁺ ions with capacities of 376 ± 15 and 117 ± 4 mg per gram of dMOR-2@CaA, respectively, while displaying the capability for simultaneous removal of various heavy metal ions in low initial concentrations and in the presence of large excesses of other cationic species. Structural and spectroscopic studies with model ligands analogous to our material's receptor unit showed chelation to the 2-picolylamine moiety to be the main binding mode of metal ions to dMOR-2. Overall, dMOR-2 is shown to represent a rare example of a MOF, which combines sensitive fluorescence detection and high sorption capacity for heavy metal ions.

Transition metal(ii) complexes of halogenated derivatives of (E)-4-(2-(pyridin-2-ylmethylene)hydrazinyl)quinazoline: structure, antioxidant activity, DNA-binding DNA photocleavage, interaction with albumin and in silico studies

Six transition metal(ii) complexes with halogenated quinazoline derivatives as ligands were characterized and evaluated for interaction with calf-thymus DNA, photocleavage of plasmid-DNA, affinity for bovine serum albumin, and antioxidant activity.

Zinc(ii) complexes of 3-bromo-5-chloro-salicylaldehyde: characterization and biological activity

Zinc(ii) complexes of 3-bromo-5-chloro-salicylaldehyde were isolated, and showed DNA- and albumin-binding affinity and antioxidant and antimicrobial properties.

Biocompatible silver(I) complexes with heterocyclic thioamide ligands for selective killing of cancer cells and high antimicrobial activity - A combined in vitro and in silico study

A series of heteroleptic Ag(I) complexes bearing 4,6-dimethyl-2-pyrimidinethiol (dmp2SH), i.e., [AgCl(dmp2SH)(PPh₃)₂] (1), [Ag(dmp2SH)(PPh₃)₂]NO₃ (2), [Ag(dmp2SΗ)(xantphos)]NO₃ (3), [Ag(μ-dmp2S)(PPh₃)]₂ (4), [Ag(dmp2S)(xantphos)] (5), [Ag(μ-dmp2S)(DPEphos)]₂ (6) (xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene and DPEPhos = bis[(2-diphenylphosphino)phenyl]ether) were synthesized. The complexes display systematic variation of particular structural characteristics which were proved to have a significant impact on their in vitro cytotoxicity and antimicrobial properties. A moderate-to-high potential for bacteria growth inhibition was observed for all complexes, with 2, 3 and 5 being particularly effective against Gram-(+) bacteria (IC₅₀ = 1.6-4.5 μM). The three complexes exhibit high in vitro cytotoxicity against HeLa and MCF-7 cancer cells (IC₅₀ = 0.32-3.00 μΜ), suggesting the importance of coordination unsaturation and cationic charge for effective bioactivity. A very low cytotoxicity against HDFa normal cells was observed, revealing a high degree of selectivity (selectivity index ~10) and, hence, biocompatibility. Fluorescence microscopy using 2 showed effective targeting on the membrane of the HeLa cancer cells, subsequently inducing cell death. Binding of the complexes to serum albumin proteins is reasonably strong for potential uptake and subsequent release to target sites. A moderate in vitro antioxidant capacity for free radicals scavenging was observed and a low potential to destroy the double-strand structure of calf-thymus DNA by intercalation, suggesting likely implication of these properties in the bioactivity mechanisms of these complexes. Further insight into possible mechanisms of bioactivity was obtained by molecular modeling calculations, by exploring their ability to act as potential inhibitors of DNA-gyrase, human estrogen receptor alpha, human cyclin-dependent kinase 6, and human papillomavirus E6 oncoprotein.

Manganese(II) complexes of substituted salicylaldehydes and α-diimines: Synthesis, characterization and biological activity

The interaction of Mn⁺² with substituted salicylaldehydes (X-saloH) led to the formation of five manganese(II) complexes formulated as [Μn(X-salo)₂(MeOH)₂]. When the reactions took place in the presence of an α-diimine such as 2,2'-bipyridine, 1,10-phenanthroline or 2,2'-bipyridylamine, five manganese(II) complexes of the formula [Mn(X-salo)₂(α-diimine)] were isolated. The characterization of the complexes was accomplished by various spectroscopic techniques and single-crystal X-ray crystallography. The antioxidant activity of the compounds was evaluated via the scavenging of 1,1-diphenyl-picrylhydrazyl, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and hydroxyl free radicals. The antibacterial activity of the complexes was tested in vitro against Staphylococcus aureus and Xanthomonas campestris bacterial strains and was found moderate. Diverse techniques were employed to examine the interaction of the complexes with calf-thymus DNA which showed intercalation as the most possible interaction mode. The affinity of the complexes for bovine serum albumin was investigated by fluorescence emission spectroscopy and the binding constants were determined.

Zinc(II) complexes of 3,5-dibromo-salicylaldehyde and α-diimines: Synthesis, characterization and in vitro and in silico biological profile

The synthesis of five neutral zinc(II) complexes of 3,5-dibromo-salicyladehyde (3,5-diBr-saloH) in the presence of nitrogen-donor co-ligands 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen), 2,9-dimethyl-1,10-phenanthroline (neoc), or 2,2'-bipyridylamine (bipyam) was undertaken and complexes [Zn(3,5-diBr-salo)₂(H₂O)₂] (1), [Zn(3,5-diBr-salo)₂(bipy)] (2), [Zn(3,5-diBr-salo)₂(phen)]^.3,5-diBr-saloΗ (3), [Zn(3,5-diBr-salo)₂(neoc)] (4) and [Zn(3,5-diBr-salo)₂(bipyam)] (5) were characterized by various techniques. The crystal structures of complexes 3 and 5 were determined by X-ray crystallography, revealing the co-existence of two different coordination modes of 3,5-diBr-salo^- ligands. The new complexes show selective in vitro antibacterial activity against two Gram-positive and two Gram-negative bacterial strains. The complexes may scavenge 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radicals and reduce H₂O₂. The complexes may intercalate in-between the calf-thymus DNA-bases and have exhibited low-to-moderate ability to cleave supercoiled circular pBR322 plasmid DNA. The complexes may bind tightly and reversibly to bovine and human serum albumins. In order to explain the in vitro activity of the compounds, molecular docking studies were adopted on the crystal structure of calf-thymus DNA, human and bovine serum albumin, Escherichia coli and Staphylococcus aureus DNA-gyrase, 5-lipoxygenase, and 5-lipoxygenase activating protein. The employed in silico studies aimed to explore the ability of the compounds to bind to these target biomacromolecules, establishing a possible mechanism of action and were in accordance with the in vitro studies.

Copper(II) complexes with non-steroidal anti-inflammatory drugs: Structural characterization, in vitro and in silico biological profile

Six novel copper(II) complexes with the non-steroidal anti-inflammatory drugs ibuprofen, loxoprofen, fenoprofen and clonixin as ligands were synthesized and characterized by diverse techniques including single-crystal X-ray crystallography. The in vitro scavenging activity of the complexes against 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) free radicals and the ability to reduce H₂O₂ were studied in the context of the antioxidant activity studies. The complexes may interact with calf-thymus DNA via intercalation as revealed by the techniques employed. The affinity of the complexes for bovine and human serum albumins was evaluated by fluorescence emission spectroscopy and the corresponding binding constants were determined. Molecular docking simulations on the crystal structure of calf-thymus DNA, human and bovine serum albumins were also employed in order to study in silico the ability of the studied compounds to bind to these target biomacromolecules, in terms of impairment of DNA and transportation through serum albumins, to explain the observed in vitro activity and to establish a possible mechanism of action.

Synthesis, characterization and (in vitro and in silico) biological activity of a series of dioxouranium(VI) complexes with non-steroidal anti-inflammatory drugs

The reaction of the dioxouranium(VI) ion with a series of non-steroidal anti-inflammatory drugs (NSAIDs), namely mefenamic acid, indomethacin, diclofenac, diflunisal and tolfenamic acid, as ligands in the absence or presence of diverse N,N'-donors (1,10-phenanthroline,2,2'-bipyridine or 2,2'-bipyridylamine) as co-ligands led to the formation of ten complexes bearing the formulas [UO₂(NSAID-O,O')₂(O-donor)₂] or [UO₂(NSAID-O,O')₂(N,N'-donor)], respectively. The complexes were characterized with diverse spectroscopic techniques and the crystal structures of three complexes were determined by single-crystal X-ray crystallography. The biological profile of the resultant complexes was assessed in vitro and in silico. The in vitro studies include their antioxidant properties (ability to scavenge free radicals 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and to reduce H₂O₂), their interaction with DNA (linear calf-thymus DNA or supercoiled circular pBR322 plasmid DNA) and their affinity for serum albumins (bovine and human serum albumin). In silico molecular docking calculations were performed regarding the behavior of the complexes towards DNA and their binding to both albumins.

Ciprofloxacin conjugated to diphenyltin(IV): a novel formulation with enhanced antimicrobial activity

The metalloantibiotic of formula Ph2Sn(CIP)2 (CIPTIN) (HCIP = ciprofloxacin) was synthesized by reacting ciprofloxacin hydrochloride (HCIP·HCl) (an antibiotic in clinical use) with diphenyltin dichloride (Ph2SnCl2DPTD). The complex was characterized in the solid state by melting point, FT-IR, X-ray Powder Diffraction (XRPD) analysis, 119Sn Mössbauer spectroscopy, X-ray Fluorescence (XRF) spectroscopy, and Thermogravimetry/Differential Thermal Analysis (TG-DTA) and in solution by UV-Vis, 1H NMR spectroscopic techniques and Electrospray Ionisation Mass Spectrometry (ESI-MS). The crystal structure of CIPTIN and its processor HCIP was also determined by X-ray crystallography. The antibacterial activity of CIPTIN, HCIP·HCl, HCIP and DPTD was evaluated against the bacterial species Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis), by the means of Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and Inhibition Zones (IZs). CIPTIN shows lower MIC values than those of HCIP·HCl (up to 4.2-fold), HCIP (up to 2.7-fold) or DPTD (>135-fold), towards the tested microbes. CIPTIN is classified into bactericidal agents according to MBC/MIC values. The developing IZs are 40.8 ± 1.5, 34.0 ± 0.8, 36.0 ± 1.1 and 42.7 ± 0.8 mm, respectively which classify the microbes P. aeruginosa, E. coli, S. aureus and S. epidermidis to susceptible ones to CIPTIN. These IZs are greater than the corresponding ones of HCIP·HCl by 1.1 to 1.5-fold against both the tested Gram negative and Gram positive bacteria. CIPTIN eradicates the biofilm of P. aeruginosa and S. aureus more efficiently than HCIP·HCl and HCIP. The in vitro toxicity and genotoxicity of CIPTIN were tested against human skin keratinocyte cells (HaCaT) (IC50 = 2.33 μM). CIPTIN exhibits 2 to 9-fold lower MIC values than its IC50 against HaCaT, while its genotoxic effect determined by micronucleus assay is equivalent to the corresponding ones of HCIP·HCl or HCIP.

Nickel(II)-meclofenamate complexes: Structure, in vitro and in silico DNA- and albumin-binding studies, antioxidant and anticholinergic activity

Five novel nickel(II) complexes with the non-steroidal anti-inflammatory drug sodium meclofenamate (Na-mclf) have been synthesized and characterized in the absence or co-existence of the nitrogen-donors imidazole (Himi), 2,2'-bipyridylamine (bipyam), 2,2'-bipyridylketoxime (Hpko) and 2,9-dimethyl-1,10-phenanthroline (neoc); namely [Ni(mclf-O)₂(Himi)₂(MeOH)₂], [Ni(mclf-O)₂(MeOH)₄], [Ni(mclf-O)(mclf-O,O')(bipyam)(MeOH)]·0.25MeOH, [Ni(mclf-O,O')₂(neoc)] and [Ni(mclf-O)₂(Hpko-N,N')₂]·MeOH·0.5H₂O. The affinity of the complexes for calf-thymus (CT) DNA was investigated by various techniques and intercalation is suggested as the most possible interaction mode. The interaction of the complexes for bovine and human serum albumins was also investigated in order to determine the binding constants, concluding that the complexes bind reversibly to albumins for the transportation towards their target cells or tissues and their release upon arrival at biotargets. The antioxidant activity of the compounds was evaluated via their ability to scavenge 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) free radicals and to reduce H₂O₂. For the determination of the anticholinergic ability of the complexes the in vitro inhibitory activity against the enzymes acetylcholinesterase and butyrylcholinesterase was evaluated and presented promising results. The in silico molecular modeling calculations employed provide useful insights for the understanding of the mechanism of action of the studied complexes at a molecular level. This applies on both the impairment of DNA by its binding with the studied complexes and transportation through serum albumins, as well as the ability of these compounds to act as anticholinergic agents.

Structure and biological profile of transition metal complexes with (E)-4-(2-(pyridin-2-ylmethylene)hydrazinyl)quinazoline

The interaction of the recently reported quinazoline derivative (E)-4-(2-(pyridin-2-ylmethylene)hydrazinyl)quinazoline (L) with a series of metal(II) (= copper(II), nickel(II), cobalt(II) and cadmium(II)) chlorides or nitrates resulted in the formation of mononuclear complexes which were characterized by spectroscopic techniques and single-crystal X-ray crystallography, i.e. [Cu(L)₂]Cl₂·4H₂O (1·4H₂O), [Ni(L)₂]Cl₂·4H₂O (2·4H₂O), [Ni(L)₂](NO₃)₂·MeOH (3·MeOH), [Co(L)₂]Cl₂·4H₂O (4·4H₂O), [Co(L)₂](NO₃)₂·H₂O (5·H₂O), [Co(L)₂](NO₃)₃·2.5H₂O (6·2.5H₂O), [Cd(L)(Cl)₂]·H₂O (7·H₂O) and [Cd(L)(CH₃OH)(H₂O)(NO₃)](NO₃) (8). The biological profile of the complexes was further assessed in regard to their binding affinity with calf-thymus DNA, their cleavage ability towards pBluescript II KS plasmid DNA in the absence or presence of irradiation of various wavelengths, their interaction with bovine serum albumin and finally, their ability to scavenge 1,1-diphenyl-picrylhydrazyl and 2,2΄-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radicals and to reduce H₂O₂.

Trinuclear and tetranuclear iron(III) complexes with fenamates: Structure and biological profile

The interaction of FeCl₃ with the fenamate non-steroidal anti-inflammatory drugs has led to the formation and isolation of trinuclear iron(III) complexes, while in the presence of the nitrogen-donors 2,2'-bipyridine or pyridine tetranuclear iron(III) complexes were derived. The five resultant complexes were characterized by diverse techniques (including infrared, electronic and Mössbauer spectroscopy) and their crystal structures were determined by single-crystal X-ray crystallography. These complexes are the first structurally characterized Fe(III)-fenamato complexes. The complexes were evaluated for their ability to scavenge in vitro free radicals such as hydroxyl, 1,1-diphenyl-2-picrylhydrazyl and 2,2΄-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid). The in vitro binding affinity of the complexes to calf-thymus (CT) DNA was examined and their interaction with serum albumins was also investigated. In total, the complexes present promising activity against the radicals tested, and they may bind tightly to CT DNA possibly via intercalation and reversibly to serum albumins.

Selective Reduction of Nitroarenes to Arylamines by the Cooperative Action of Methylhydrazine and a Tris(N-heterocyclic thioamidate) Cobalt(III) Complex

We report an efficient catalytic protocol that chemoselectively reduces nitroarenes to arylamines, by using methylhydrazine as a reducing agent in combination with the easily synthesized and robust catalyst tris(N-heterocyclic thioamidate) Co(III) complex [Co(κS,N-tfmp2S)₃], tfmp2S = 4-(trifluoromethyl)-pyrimidine-2-thiolate. A series of arylamines and heterocyclic amines were formed in excellent yields and chemoselectivity. High conversion yields of nitroarenes into the corresponding amines were observed by using polar protic solvents, such as MeOH and ⁱPrOH. Among several hydrogen donors that were examined, methylhydrazine demonstrated the best performance. Preliminary mechanistic investigations, supported by UV-vis and NMR spectroscopy, cyclic voltammetry, and high-resolution mass spectrometry, suggest a cooperative action of methylhydrazine and [Co(κS,N-tfmp2S)₃] via a coordination activation pathway that leads to the formation of a reduced cobalt species, responsible for the catalytic transformation. In general, the corresponding N-arylhydroxylamines were identified as the sole intermediates. Nevertheless, the corresponding nitrosoarenes can also be formed as intermediates, which, however, are rapidly transformed into the desired arylamines in the presence of methylhydrazine through a noncatalytic path. On the basis of the observed high chemoselectivity and yields, and the fast and clean reaction processes, the present catalytic system [Co(κS,N-tfmp2S)₃]/MeNHNH₂ shows promise for the efficient synthesis of aromatic amines that could find various industrial applications.

Copper(II) complexes with meclofenamate ligands: Structure, interaction with DNA and albumins, antioxidant and anticholinergic activity

The interaction of copper(II) with the non-steroidal anti-inflammatory drug sodium meclofenamate (Na-mclf) in the presence or absence of the nitrogen-donor co-ligands pyridine (py) or 2,2'-bipyridylamine (bipyam), yielded the novel Cu(II) complexes [Cu₂(mclf-O,O')₄(MeOH)₂]·2MeOH (1·2MeOH), [Cu(mclf-O)₂(py)₃]·H₂O·0.5MeOH (2·H₂O·0.5MeOH) and [Cu(mclf-O,O')₂(bipyam)] (3). The characterization of the complexes was achieved by various techniques, including single-crystal X-ray crystallography. In order to study the binding mode and strength of the complexes to calf-thymus (CT) DNA, various techniques were employed which suggested intercalation between the DNA-bases as the most possible interaction mode. Competitive studies with ethidium bromide (EB) revealed the ability of the complexes to displace the EB from the EB-DNA adduct, verifying the intercalative binding mode. The affinity of the complexes to bovine and human serum albumin proteins (SAs) was investigated by fluorescence emission spectroscopy and the corresponding binding constants bear relatively high values, showing that the complexes bind tightly and possibly reversibly to SAs. The antioxidant activity of the complexes against 1,1-diphenyl-picrylhydrazyl (DPPH), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals and the ability to reduce H₂O₂ proved to be of significant magnitude. The in vitro inhibitory activity against the enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) was evaluated, in order to assess the anticholinergic ability of the complexes, which appeared promising.

Synthesis, structural determination, in vitro and in silico biological evaluation of divalent or trivalent cobalt complexes with indomethacin

The interaction of cobalt chloride with the non-steroidal anti-inflammatory drug indomethacin (Hindo) led to the formation of the polymeric complex [Co(indo-O)2(H2O)2(μ-Cl)]n·n(MeOH·H2O) bearing one chlorido bridge between the cobalt atoms. The presence of the nitrogen-donor co-ligands 2,2'-bipyridine (bipy), 2,2'-bipyridylamine (bipyam), 1,10-phenanthroline (phen) or 1H-imidazole (Himi) resulted in the isolation of complexes [Co2(μ-indo-O,O')2(indo-O)2(bipy)2(μ-H2O)]·3.3MeOH, [Co(indo-O,O')2(bipyam)]·0.9MeOH·0.2H2O, [Co(indo-O,O')2(phen)] (4) and [Co(indo-O)2(Himi)2] (5), respectively, where the indomethacin ligands were coordinated in diverse manners. The study of the affinity of the complexes for calf-thymus DNA revealed their intercalation between the DNA-bases. The binding of the complexes to albumins was also examined and the corresponding binding constants and binding subdomain were determined. The free radical scavenging activity of the compounds was evaluated towards 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid). Molecular modeling calculations may usually provide a molecular basis for the understanding of both the impairment of DNA by its binding with the studied complexes and the ability of these compounds to transportation through serum albumin proteins. This study can provide information for the elucidation of the mechanism of action of the compounds in a molecular level.

Silver complexes with heterocyclic thioamide and tertiary arylphosphane ligands: Synthesis, crystal structures, in vitro and in silico antibacterial and cytotoxic activity, and interaction with DNA

Herein we report on the synthesis and molecular structures of six silver(I) mixed-ligand complexes containing a heterocyclic thioamide [4-phenyl-imidazole-2-thione (phimtH) or 2,2,5,5-tetramethyl-imidazolidine-4-thione (tmimdtH)] and a tertiary arylphosphane [triphenylphosphine (PPh₃), tri-o-tolylphosphane (totp)] or diphosphane [(1,2-bis(diphenylphosphano)ethane (dppe), bis(2-diphenylphosphano-phenyl)ether (DPEphos) or 4,5-bis(diphenylphosphano)-9,9-dimethylxanthene) (xantphos)]. The interaction of the compounds with calf-thymus DNA (CT DNA), as monitored directly via UV-vis spectroscopy and DNA-viscosity measurements and indirectly via its competition with ethidium bromide for DNA-intercalation sites, is suggested to take place via an intercalative mode. The new complexes show selective significant in vitro antibacterial activity against four bacterial strains. The antiproliferative effects and cytostatic efficacies of the complexes against four human cancer cell lines were evaluated. The best cytostatic and cytotoxic activity was appeared for the complexes bearing the phimtH moiety. In order to explain the described in vitro activity of the complexes, and to approach a possible mechanism of action, molecular docking studies were adopted on the crystal structure of CT DNA, DNA-gyrase, human estrogen receptor alpha and a cell-cycle specific target protein, human cyclin-dependent kinase 6.

A palladium(II) complex with the Schiff base 4-chloro-2-(N-ethyliminomethyl)-phenol: Synthesis, structural characterization, and in vitro and in silico biological activity studies

The synthesis and characterization of the Pd(II) complex of the formula [Pd(L)₂] 1 with the Schiff base 4-chloro-2-(N-ethyliminomethyl)-phenol (HL) as derived in situ via the condensation reaction of 5-chloro-salicylaldehyde and ethylamine was undertaken. The structure of 1 was verified by single-crystal X-ray crystallography. The ability of 1 to interact with calf-thymus (CT) DNA was studied by UV-vis and viscosity experiments, and its ability to displace ethidium bromide (EB) from the DNA-EB conjugate was revealed by fluorescence spectroscopy. It was found that intercalation is the most possible mode of interaction with CT DNA. Additionally, DNA electrophoretic mobility experiments showed that 1 interacts with the plasmid pBluescript SK(+) (pDNA) as proved by the formation of unusual mobility DNA bands and degradation of relaxed pDNA at concentration of 5 mM. The interaction of 1 with human (HSA) and bovine serum albumin (BSA) was monitored revealing its reversible binding to albumins. The complex showed noteworthy antimicrobial activity against one (Bacillus subtilis) of the five tested bacteria. In order to explain the described in vitro activity of the compound, we adopted molecular docking studies on the crystal structure of HSA, BSA, CT DNA and DNA-gyrase. Furthermore, in silico predictive tools have been employed to study the properties of the complex. The in silico studies are adopted on a multitude of proteins involved in cancer growth, as well as prediction of drug-induced changes of gene expression profile, protein- and mRNA-based prediction results, prediction of sites of metabolism, cytotoxicity for cancer cell lines, etc.

Diclofenac conjugates with biocides through silver(I) ions (CoMeD's); Development of a reliable model for the prediction of anti-proliferation of NSAID's-silver formulations

The conjugation of diclofenac (DICLH), a Non-Steroidal Anti-inflammatory Drug (NSAID), with biocides such as dimethyl sulfoxide (DMSO) and triphenylphosphine (TPP), through silver(I) ions, results into the chemical [Ag_n(DICL)_n(L)_m]_k (L = DMSO and n = 2, m = 2, k = infinite (1); L = TPP and n = 1, m = 2, k = 1 (2)). The compounds were characterized by m.p., FT-IR, UV-vis and ¹H NMR spectroscopic techniques. The crystal and molecular structures of 1-2 were determined by X-ray crystallography. The in vitro cytotoxic activity of 1-2 against the human breast adenocarcinoma cancer cells MCF-7 (hormone dependent) and MDA-MB-231 (hormone independent) reveals that the 1 inhibits the MCF-7 rather than the MDA-MB-231 cells, suggesting hormone mimetic behaviour. Compound 2 inhibits both cancerous cell lines, stronger than cisplatin. Both compounds inhibit MCF-7 cells migration. Compounds 1-2, exhibit, lower toxicity against fetal lung fibroblast (MRC-5) cells than cisplatin. Their genotoxicity was evaluated on MRC-5 cells. The molecular mechanism of 1-2 against MCF-7 cells was clarified by (i) their cell cycle arrest study (ii) their mitochondrial membrane permeability (iii) their binding affinity towards Calf Thymus (CT)-DNA and (iv) their inhibitory activity against the enzyme lipoxygenase (LOX). Regression analysis of the data obtained for [Ag(NSAID)(Ar₃P)_m] (NSAID = p‑hydroxy‑benzoic acid (p-HO-BZAH), salicylic acid (SALH₂), aspirin (ASPH), naproxen (NAPRH), nimesulide (NIMH); L = TPP, Tri(p‑tolyl)phosphine (TPTP), Tri(o‑tolyl)phosphine (TOTP), Tri(m‑tolyl)phosphine (TMTP); m = 2 or 3) and [Ag(DICL)₂(DMSO)₂]_k (k = infinite) was performed. Considering the biological results (IC₅₀) as dependent variable a theoretical equation is obtained for these compounds. The calculated IC₅₀ values are compared satisfactorily with the corresponding experimental inhibitory activity of the complexes.

Silver complex of salicylic acid and its hydrogel-cream in wound healing chemotherapy

The known metallotherapeutic [Ag(salH)]₂ (AGSAL-1) of salicylic acid (salH₂), was used for the development of new efficient silver based material for wounds healing. AGSAL-1 was characterized by spectroscopic techniques and X-ray crystallography. The wound healing epithelialization of AGSAL-1 was investigated by the means of scratch assay against immortalized human keratinocytes (HaCaT) cells. The anti-inflammatory activity of AGSAL-1 was evaluated by monitoring the catalytic peroxidation of linoleic acid to hydroperoxylinoleic acid by the enzyme lipoxygenase (LOX). The antibacterial activity of AGSAL-1 was evaluated against bacterial species which colonize wounds, such as: Pseudomonas aeruginosa (PAO1), Staphylococcus epidermidis and Staphylococcus aureus, by the means of Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and their Inhibition Zone (IZ). Moreover, the influence of AGSAL-1 against the formation of biofilm of PAO1 and St. aureus was also evaluated by the mean of Biofilm Elimination Concentration (ΒΕC). A hydrogel material CMC@AGSAL-1, based on the dispersion of AGSAL-1 in to carboxymethyl cellulose (CMC) was tested for its antimicrobial activity. Molecular Docking was performed, to explore the molecular interaction of AGSAL-1 with (i) the transcriptional regulator of PAO1, LasR. (ii) the mevalonate pathway for the biosynthesis of isoprenoids which is essential for gram-positive bacteria St. epidermidis and St. aureus. The toxicity of AGSAL-1 was examined against the HaCaT cells. Its genotoxicity was evaluated using Allium cepa model, in vivo. No genotoxicity was detected, indicating that AGSAL-1 is a candidate towards the development on a new efficient medication of the silver based metallodrugs.