6,6″-Dimethyl-2,2′:6′,2″-terpyridine revisited: New fluorescent silver(I) helicates with in vitro antiproliferative activity via selective nucleoli targeting

The effect of ionic versus covalent functionalization of polyoxometalate hybrid materials with coordinating subunits on their stability and interaction with DNA

Inorganic-organic hybrid materials that combine both Polyoxometalates (POMs) and metal ion coordinating subunits (CSUs) represent promising multifunctional materials. Though their individual components are often biologically active, utilization of hybrid materials in bioassays significantly depends on the functionalization method and thus resulting stability of the system. Quite intriguingly, these aspects were very scarcely studied in hybrid materials based on the Wells-Dawson POM (WD POM) scaffold and remain unknown. We chose two model WD POM hybrid systems to establish how the functionalization mode (ionic vs. covalent) affects their stability in biological medium and interaction with nucleic acids. The synthetic scope and limitations of the covalent POM-terpyridine hybrids were demonstrated and compared with the ionic Complex-Decorated Surfactant Encapsulated-Clusters (CD-SECs) hybrids. The nature of POM and CSU binding can be utilized to modulate the stability of the hybrid and the extent of DNA binding. The above systems show potential to behave as model cargo-platforms for potential utilization in medicine and pharmacy.

The Therapeutic Potential in Cancer of Terpyridine-Based Metal Complexes Featuring Group 11 Elements

Terpyridine-based complexes with group 11 metals emerge as potent metallodrugs in cancer therapy. This comprehensive review focuses on the current landscape of anticancer examples, particularly highlighting the mechanisms of action. While Cu(II) complexes, featuring diverse ancillary ligands, dominate the field, exploration of silver and gold species remains limited. These complexes exhibit significant cytotoxicity against various cancer cell lines with a commendable selectivity for non-tumorigenic cells. DNA interactions, employing intercalation and groove binding, are pivotal and finely tuned through terpyridine ligand functionalization. In addition, copper complexes showcase nuclease activity, triggering apoptosis through ROS generation. Despite silver's high affinity for nitrogen donor atoms, its exploration is relatively sparse, with indications of acting as intercalating agents causing DNA hydrolytic cleavage. Gold(III) compounds, overshadowing gold(I) due to stability concerns, not only intercalate but also induce apoptosis and disrupt the mitochondrial membrane. Further investigations are needed to fully understand the mechanism of action of these compounds, highlighting the necessity of exploring additional biological targets for these promising metallodrugs.

New N4-Donor Ligands as Supramolecular Guests for DNA and RNA: Synthesis, Structural Characterization, In Silico, Spectrophotometric and Antimicrobial Studies

The present work reports the synthesis of new N4-donor compounds carrying p-xylyl spacers in their structure. Different Schiff base aliphatic N-donors were obtained synthetically and subsequently evaluated for their ability to interact with two models of nucleic acids: calf-thymus DNA (CT-DNA) and the RNA from yeast Saccharomyces cerevisiae (herein simply indicated as RNA). In more detail, by condensing p-xylylenediamine and a series of aldehydes, we obtained the following Schiff base ligands: 2-thiazolecarboxaldehyde (L1), pyridine-2-carboxaldehyde (L2), 5-methylisoxazole-3-carboxaldehyde (L3), 1-methyl-2-imidazolecarboxaldehyde (L4), and quinoline-2-carboxaldehyde (L5). The structural characterisation of the ligands L1-L5 (X-ray, ¹H NMR, ¹³C NMR, elemental analysis) and of the coordination polymers {[CuL1]PF₆}_n (herein referred to as Polymer1) and {[AgL1]BF₄}_n, (herein referred to as Polymer2, X-ray, ¹H NMR, ESI-MS) is herein described in detail. The single crystal X-ray structures of complexes Polymer1 and Polymer2 were also investigated, leading to the description of one-dimensional coordination polymers. The spectroscopic and in silico evaluation of the most promising compounds as DNA and RNA binders, as well as the study of the influence of the 1D supramolecular polymers Polymer1 and Polymer2 on the proliferation of Escherichia coli bacteria, were performed in view of their nucleic acid-modulating and antimicrobial applications. Spectroscopic measurements (UV-Vis) combined with molecular docking calculations suggest that the thiazolecarboxaldehyde derivative L1 is able to bind CT-DNA with a mechanism different from intercalation involving the thiazole ring in the molecular recognition and shows a binding affinity with DNA higher than RNA. Finally, Polymer2 was shown to slow down the proliferation of bacteria much more effectively than the free Ag(I) salt.

New Cu(i) square grid-type and Ni(ii) triangle-type complexes: synthesis and characterization of effective binders of DNA and serum albumins

Metallosupramolecular square grid-type complex [Cu4L4]4+ and triangle-type complex [Ni3L3]6+ as a potential strategy for obtaining versatile metal-based DNA, Serum Albumin (SA) and DNA binders.

Helicity-driven chiral self-sorting supramolecular polymerization with Ag+: right- and left-helical aggregates

The study of chiral self-sorting is extremely important for understanding biological systems and for developing applications for the biomedical field. In this study, we attempted an unprecedented chiral self-sorting supramolecular...

Synthesis and Spectroscopic Investigations of Schiff Base Ligand and Its Bimetallic Ag(I) Complex as DNA and BSA Binders

Generation of well-defined potential metallotherapeutics for cancer treatment, one of the most population-threatening diseases, is challenging and an active area of modern research in view of their unique properties and thus multiple possible pathways of action in cells. Specifically, Schiff base ligands were recognized as very promising building blocks for the construction of stable and active complexes of numerous geometries and topologies. Incorporation of Ag(I) ions allows for the formation of flat complexes with potential unoccupied coordination sites, thus giving rise to specific interactions between the metallotherapeutic and biomolecule of interest. Herein, we present the design, synthesis and characterization of new Schiff base ligand L and its Ag(I) bimetallic complex [Ag2L2]2+ with two planar moieties formed around the metal ions and connected through cyclohexane rings, confirmed by X-ray measurements. The compounds were described in context of their potential use as anticancer drugs through DNA and BSA binding pathways by several spectroscopic methods (CD, UV-Vis, fluorescence). We revealed that both, L and [Ag2L2]2+, interact with similar affinity with CT-DNA (Kb~106 M-1), while they differ in the type and strength of interactions with the model albumin-BSA. [Ag2L2]2+ binds BSA in both a dynamic and static manner with the Ksv = 8.8 × 104 M-1 in the Trp-134 and Trp-213 sites, whereas L interacts with BSA only dynamically (KSV = 2.4 × 104 M-1). This found further confirmation in the CD studies which revealed a reduction in α-helix content in the albumin of 16% in presence of [Ag2L2]2+.

Zinc Complexes with Nitrogen Donor Ligands as Anticancer Agents

The search for anticancer metal-based drugs alternative to platinum derivatives could not exclude zinc derivatives due to the importance of this metal for the correct functioning of the human body. Zinc, the second most abundant trace element in the human body, is one of the most important micro-elements essential for human physiology. Its ubiquity in thousands of proteins and enzymes is related to its chemical features, in particular its lack of redox activity and its ability to support different coordination geometries and to promote fast ligands exchange. Analogously to other trace elements, the impairment of its homeostasis can lead to various diseases and in some cases can be also related to cancer development. However, in addition to its physiological role, zinc can have beneficial therapeutic and preventive effects on infectious diseases and, compared to other metal-based drugs, Zn(II) complexes generally exert lower toxicity and offer few side effects. Zinc derivatives have been proposed as antitumor agents and, among the great number of zinc coordination complexes which have been described so far, this review focuses on the design, synthesis and biological studies of zinc complexes comprising N-donor ligands and that have been reported within the last five years.

Synthesis, structure, fluorescence, and electrochemical properties of a binuclear Ag(I) complex with 1,4-bis(benzo[d]oxazol-2-yl)butane as a ligand

Reaction of 1,4-bis(benzo[d]oxazol-2-yl)butane (BBO) with [Ag(CH3CN)4(ClO4)] afforded a new binuclear silver(I) complex, with composition [Ag2(BBO)2(ClO4)2], characterized by elemental analysis, UV/Vis and IR spectroscopy, and single-crystal X-ray diffraction. The results show that the Ag(I) complex consists of a centrosymmetric dimetallacyclic structure assembled from two Ag(I) atoms and two bridging BBO ligands. The coordination environment of silver(I) complex can be described as distorted trigonal planar, with one oxygen atom from a perchlorate anion and two nitrogen atoms from two BBO ligands. The luminescence properties of the ligand and the Ag(I) complex were studied in the solid state. The emission peaks of the Ag(I) complex are attributed to ligand-centered transitions. There is no effect of the complexation except for a partial quenching. The cyclic voltammograms of the Ag(I) complex indicated an irreversible Ag+/Ag couple.

New Artificial Biomimetic Enzyme Analogues based on Iron(II/III) Schiff Base Complexes: An Effect of (Benz)imidazole Organic Moieties on Phenoxazinone Synthase and DNA Recognition

Elucidation of the structure and function of biomolecules provides us knowledge that can be transferred into the generation of new materials and eventually applications in e.g., catalysis or bioassays. The main problems, however, concern the complexity of the natural systems and their limited availability, which necessitates utilization of simple biomimetic analogues that are, to a certain degree, similar in terms of structure and thus behaviour. We have, therefore, devised a small library of six tridentate N-heterocyclic coordinating agents (L¹-L⁶), which, upon complexation, form two groups of artificial, monometallic non-heme iron species. Utilization of iron(III) chloride leads to the formation of the 1:1 (Fe:L_n) 'open' complexes, whereas iron(II) trifluoromethanosulfonate allows for the synthesis of 1:2 (M:L_n) 'closed' systems. The structural differences between the individual complexes are a result of the information encoded within the metallic centre and the chosen counterion, whereas the organic scaffold influences the observed properties. Indeed, the number and nature of the external hydrogen bond donors coming from the presence of (benz)imidazole moieties in the ligand framework are responsible for the observed biological behaviour in terms of mimicking phenoxazinone synthase activity and interaction with DNA.

Light-stable polypyridine silver(i) complexes of 1,3,5-triaza-7-phosphaadamantane (PTA) and 1,3,5-triaza-7-phosphaadamantane-7-sulfide (PTA[double bond, length as m-dash]S): significant antiproliferative activity of representative examples in aqueous media

A series of novel silver(i) 2,2':6',2''-terpyridine (tpy), 4'-(4-methylphenyl)-2,2':6':2''-terpyridine (tpy-Ph-Me) and 1,10-phenanthroline-5,6-dione (dione) derivatives containing PTA (1,3,5-triaza-7-phosphaadamantane) or 1,3,5-triaza-7-phosphaadamantane-7-sulfide (PTA[double bond, length as m-dash]S) have been synthesized and fully characterized. Two types of complexes have been obtained, monocationic [Ag(tpy)(PTA)](NO₃) (1), [Ag(tpy-Ph-Me)(PTA)](NO₃) (2), [Ag(dione)(PTA[double bond, length as m-dash]S)](BF₄) (4) and [Ag(dione)₂](PF₆) (5) and neutral [Ag(dione)(PTA[double bond, length as m-dash]S)(NO₃)] (3). The solid-state structures of four complexes have been determined by single-crystal X-ray diffraction. Complexes 1 and 2 are luminescent at room temperature and 77 K while 5 shows emission only at 77 K. Compounds 3 and 4 are not emissive. Furthermore, representative light-stable and water-soluble 1 and 3 were evaluated for their cytotoxic activities on the normal human dermal fibroblast (NHDF) cell line and their antitumor activity using the human lung carcinoma (A549), epithelioid cervix carcinoma (HeLa) and human breast adenocarcinoma (MCF-7) cell lines. Interactions between the complexes and human serum albumin (HSA) using UV-Vis, fluorescence and circular dichroism spectroscopy (CD) were also investigated.

The first example of an asymmetrical μ-oxo bridged dinuclear iron complex with a terpyridine ligand

The reaction of Fe(iii) ions with a terpyridine ligand L in the presence of chlorides and independent of conditions results in the formation of μ-oxo bridged dinuclear [FeLCl(μ-O)FeCl₃] and the mononuclear complex [FeLCl₂].

Silver(i) complexes of bis- and tris-(pyrazolyl)azine derivatives - dimers, coordination polymers and a pentametallic assembly

Silver(i) complexes of 2,4,6-tri(pyrazol-1-yl)pyridine (tpp), 2,4,6-tri(pyrazol-1-yl)pyrimidine (tpym), 2,4,6-tri(pyrazol-1-yl)-1,3,5-triazine (tpt) and 2,4-di(pyrazol-1-yl)-1,3,5-triazine (bpt) are reported. Dinuclear [Ag2(μ-tpp)2(MeCN)2][BF4]2·2MeCN and [Ag2(μ-tpym)2(MeCN)2][BF4]2 are formed from approximately planar [AgL(NCMe)]+ (L = tpp or bpym) centres, which dimerise via apical interactions to the pendant pyrazolyl donor on each ligand. Two polymeric solvatomorph phases [Ag2(μ-tpp)2][BF4]2·nMeNO2 were obtained by crystallising AgBF4 and tpp from nitromethane solution. One is composed of the same dimeric [Ag2(μ-tpp)2]2+ motif as the MeCN solvates, but with semibridging pyrazolyl substitutents replacing the solvent ligands. The other form has helicate [Ag2(μ-tpp)2]2+ dimers linked into chains by unsupported AgAg interactions. In contrast, [Ag5(μ3-tpym)4][BF4]5·2MeNO2 contains discrete pentametallic assemblies, of a flattened [Ag4(μ-tpym)4]4+ molecular square centred by the fifth silver ion. Three helical or linear 1D coordination polymer topologies are described for [Ag(μ-tpt)]X (X- = BF4- or ClO4-), where ditopic tpt ligands bind one silver ion in a [2 + 1] geometry and the other in bidentate, [1 + 1] or monodentate fashion. Finally, [Ag(bpt)]BF4 is a polymer of square planar silver ions linked by bis-bidentate bpt ligands. Most of the tpt and bpt structures include short anionπ contacts to the ligand triazinyl rings. Electrospray mass spectra confirm the oligomeric nature of the Ag/tpym and tpt complexes in MeNO2 solution.

Full characterization and cytotoxic activity of new silver(i) and copper(i) helicates with quaterpyridine

DNA binding and cells' cycle disorders caused by four new dinuclear Ag(i) and Cu(i) double helicates with quaterpyridine ligands.

Synthesis, crystal structure, and DNA-binding studies of different coordinate binuclear silver(i) complexes with benzimidazole open-chain ether ligands

Three new binuclear silver(i) complexes with bis-benzimidazole ligands have been developed and they bind to CT-DNA in an intercalation mode.