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Abstract Complex compounds [CuL(phen)(H2O)(NO3)]NO3 (1), [CuL(bipy)(NO3)2]·2EtOH (2), [CuL2(H2O)2 (NO3)2] (2a), [CuL(dmbipy)(NO3)2]·3EtOH (3), and [CuL2(NO3)2] (3a), where L is 3-(5-phenyl-2H-tetrazol-2-yl)pyridine, phen is 1,10-phenanthroline, bipy is 2,2′-bipyridine, and dmbipy is 4,4′-dimethyl-2,2′-bipyridine, are obtained and structurally characterized. It is shown that L behaves as the monodentate ligand being coordinated by the nitrogen atom of the pyridine ring. The coordination polyhedron made of copper atoms is a square pyramid in complexes 1 and 3, a distorted octahedron and a distorted square in complexes 2a and 3a respectively. Complex 1 is characterized by the elemental analysis, powder X-ray diffraction, and IR spectroscopy. Furthermore, its cytotoxic properties are studied on human larynx carcinoma (Hep2), breast adenocarcinoma (MCF7), and non-tumor human fibroblast (MRC5) cell lines. Complex 1 is shown to exhibit the pronounced cytotoxic action (LC50(Hep2) = 4.1±0.4 µM and LC50(MCF7) = 4.9±0.1 µM), however, does not exhibit selectivity against tumor cell lines (LC50(MRC5) = = 3.06 ±0.02 µM). Show less

Three copper(II) complexes – [Cu2(bipy)2L4] (1), [Cu2(phen)2L4] (2) and [Cu2(dmphen)2L4]·2H2O (3) – were synthesized based on 5-methyltetrazole (HL) and 2,2′-bipyridine/1,10-phenanthroline derivatives. A crystallographic study revealed that complexes 1–3 have a binuclear structure with coordination polyhedron close to the square pyramid. Stability of the complexes in aqueous solution was studied by UV-Vis spectroscopy and conductometry. In vitro cytotoxicity study was carried out in 2D and 3D cell culture models and showed that complexes 2 and 3 possess cytotoxic activity against tumor cells (A549, Hep2, HepG2, MCF7) with LC50 values exceeding those of the medical drug cisplatin. At the same time, being less active, compound 1 has a selectivity index of 3.1 to hepatocellular carcinoma (HepG2 cell line) compared to non-tumor MRC5 cells. The Hoechst/Propidium iodide staining assay and ROS generation assay on Hep2 cells indicated that the cytotoxic effects of the complexes involved apoptosis induction without ROS accumulation. Show less

Three cytotoxic copper(ii) complexes – [Cu2(bipy)2L4] (1), [Cu2(phen)2L4] (2) and [Cu2(dmphen)2L4]·2H2O (3) – were synthesized based on 5-methyltetrazole (HL) and 2,2′-bipyridine/1,10-phenanthroline derivatives. Show less

Copper(II), manganese(II), and mercury(II) complexes of 4-amino-5-(2-(1-pyridine-2-yl)ethylidene)hydrazinyl)-4H-1,2,4-triazole-3-thiol (H2TAP) were synthesized and characterized using CHN analysis, FT-IR, 1H-NMR, 13C-NMR, UV–Vis, ESR, MS, PXRD, magnetic moment measurements, molar conductance, and TG/DTA. DFT calculations indicate octahedral geometries and the neutral bidentate or tridentate chelating behavior of the ligand. Cyclic voltammetry revealed the complexes’ redox properties, and Job’s method elucidated stoichiometric compositions in solution. Biochemical assays demonstrated antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans. The MnII complex exhibited potent antitumor activity against HepG-2 cells. Antioxidant and DNA binding studies showed promising results, with docking investigations indicating strong interactions between the ligand/complexes and target proteins (PDB: 1YWN) and DNA (PDB: 8EC1), suggesting therapeutic potential. Show less

Nickel(II) complexes of 1H-tetrazol-5-acetic acid (H2L) and oligopyridines (1,10-phenanthroline /2,2’-bipyridine derivatives) have been synthesized and characterized by physicochemical methods (elemental and thermogravimetric analysis, powder X-ray diffraction, and IR spectroscopy). The behavior of the complexes in solution was studied by UV–Vis spectroscopy, conductometry, and mass spectrometry. The stability of the complexes over 48 h in aqueous solution and in phosphate-buffered saline was demonstrated using UV–Vis spectroscopy. These compounds were investigated for their cytotoxic and cytostatic activity against HepG2 (hepatocellular carcinoma), and Hep2 (larynx carcinoma) human cancer cell lines. Cytotoxicity was also studied on human non-cancerous cell line MRC-5 (lung fibroblast). All the compounds did not show cytotoxic activity against the tested cell lines in 1–50-µM concentration range. However, compounds showed a cytostatic effect against HepG2 and Hep2 cell lines. The most pronounced cytostatic properties were found for the complex [Ni(dmphen)2L]·2C2H5OH·2H2O (1). In addition, we report three new crystal structures: [Ni(phen)2L]·H2O, [Ni(dmbipy)2L]·2C2H5OH, and [Ni(dmphen)2L]·2C2H5OH·2H2O, where L2– behaves as a bidentate ligand which is coordinated to the Ni(II) ion via N,O atoms. Show less

Abstract The review is devoted to copper coordination compounds based on 2,2′-bipyridine / 1,10-phenanthroline and diverse N-, O-, S-donor ligands exhibiting cytotoxic properties. Therefore, they can be a starting platform for developing antitumor drugs. The review covers the structural aspects of the complexes, the features of their cytotoxic activity and its mechanism, as well as in vivo studies. Show less

Rhenium(I) tricarbonyl complexes are widely studied for their cell imaging properties and anti-cancer and anti-microbial activities, but the complexes with S-donor ligands remain relatively unexplored. A series of six fac-[Re(NN)(CO)3(SR)] complexes, where (NN) is 2,2′-bipyridyl (bipy) or 1,10-phenanthroline (phen), and RSH is a series of thiocarboxylic acid methyl esters, have been synthesized and characterized. Cellular uptake and anti-proliferative activities of these complexes in human breast cancer cell lines (MDA-MB-231 and MCF-7) were generally lower than those of the previously described fac-[Re(NN)(CO)3(OH2)]+ complexes; however, one of the complexes, fac-[Re(CO)3(phen)(SC(Ph)CH2C(O)OMe)] (3b), was active (IC50 ∼ 10 μM at 72 h treatment) in thiol-depleted MDA-MB-231 cells. Moreover, unlike fac-[Re(CO)3(phen)(OH2)]+, this complex did not lose activity in the presence of extracellular glutathione. Taken together these properties show promise for further development of 3b and its analogues as potential anti-cancer drugs for co-treatment with thiol-depleting agents. Conversely, the stable and non-toxic complex, fac-[Re(bipy)(CO)3(SC(Me)C(O)OMe)] (1a), predominantly localized in the lysosomes of MDA-MB-231 cells, as shown by live cell confocal microscopy (λex = 405 nm, λem = 470–570 nm). It is strongly localized in a subset of lysosomes (25 μM Re, 4 h treatment), as shown by co-localization with a Lysotracker dye. Longer treatment times with 1a (25 μM Re for 48 h) resulted in partial migration of the probe into the mitochondria, as shown by co-localization with a Mitotracker dye. These properties make complex 1a an attractive target for further development as an organelle probe for multimodal imaging, including phosphorescence, carbonyl tag for vibrational spectroscopy, and Re tag for X-ray fluorescence microscopy. Show less

A series of nine luminescent iridium(III) complexes with pH-responsive imidazole and benzimidazole ligands have been prepared and characterized. The first series of complexes were of the form [Ir(ppy)2(N^N)]+ or [Ir(ppy)2(C^N)]+ (where ppy is 2-phenylpyridine and N^N is 2-(2-pyridyl)imidazole or 2-(2-pyridyl)benzimidazole and C^N represents a pyridyl-triazolylidene-based N-heterocyclic carbene ligand). For these complexes, the benzimidazole group was either unsubstituted or substituted with electron-withdrawing (Cl) or electron-donating (Me) groups. The second series of complexes were of the form [Ir(phbim)2(N^N)]+ or [Ir(phbim)2(C^N)]+ (where phbim is 2-phenylbenzimidazole and N^N is either 2,2′-bipyridine or 1,10-phenanthroline and C^N is either a pyridyl-imidazolylidene or pyridyl-triazolylidene N-heterocyclic carbene ligand). UV-visible and photoluminescence pH titration studies showed that changing the protonation state of these complexes results in significant changes in the photoluminescence emission properties. The pKa values of prepared complexes were estimated from the spectroscopic pH titration data and these values show that the nature of the pH-sensitive ligands (either main or ancillary ligands) resulted in a significant capacity to modulate the pKa values for these compounds with values ranging from 5.19–11.22. Theoretical investigations into the nature of the electronic transitions for the different protonation states of compounds were performed and the results were consistent with the experimental results. Show less

Monofunctional platinum complexes offer a promising alternative to cisplatin in cancer chemotherapy, showing a unique mechanism of action. Their ability to induce minor helix distortions effectively inhibits DNA transcription. In our study, we synthesized and characterized three monofunctional Pt(II) complexes with the general formula [Pt(en)(L)Cl]NO3, where en = ethylenediamine, and L = pyridine (py), 2-methylpyridine (2-mepy), and 2-phenylpyridine (2-phpy). The hydrolysis rates of [Pt(en)(py)Cl]NO3 (1) and [Pt(en)(2-mepy)Cl]NO3 (2) decrease with the bulkiness of the auxiliary ligand with k(1) = 2.28 ± 0.15 × 10-4 s-1 and k(2) = 8.69 ± 0.98 × 10-5 s-1 at 298 K. The complex [Pt(en)(2-phpy)Cl]Cl (3) demonstrated distinct behavior. Upon hydrolysis, an equilibrium (Keq = 0.385 mM) between the complexes [Pt(en)(2-phpy)Cl]+ and [Pt(en)(2-phpy-H+)]+ was observed with no evidence (NMR or HR-ESI-MS) for the presence of the aquated complex [Pt(en)(2-phpy)(H2O)]2+. Despite the kinetic similarities between phenanthriplatin and (2), complexes (1) and (2) exhibit minimal activity against A549 lung cancer cell line (IC50 > 100 μΜ), whereas complex (3) exhibits notable cytotoxicity (IC50 = 41.11 ± 2.1 μΜ). In examining the DNA binding of (1) and (2) to the DNA model guanosine (guo), we validated their binding through guoN7, which led to an increased population of the C3'-endo sugar conformation, as expected. However, we observed that the rapid transition 2E (C2'-endo) ↔ 3E (C3'-endo), in the case of [Pt(en)(py)(guo)](NO3)2 ([1-guo]), slows down in the case of [Pt(en)(2-mepy)(guo)](NO3)2 ([2-guo]), resulting in separate signals for the two conformers in the 1H NMR spectra. This phenomenon arises from the steric hindrance between the methyl group of pyridine and the sugar moiety of guanosine. Notably, this hindrance is absent in [2-(9-MeG)] (9-MeG = 9-methylguanine), probably due to the absence of a bulky sugar unit in 9-MeG. In the case of (3), where the bulkiness of the substitution on the pyridine is further increased by a phenyl group, we observed a notable proximity between 9-MeGH8 and the phenyl ring of 2-phpy. Considering that only (3) exhibited good cytotoxicity against the A549 cancer cell line, it is suggested that auxiliary ligands, L, with an extended aromatic system and proper orientation in complexes of the type cis-[Pt(en)(L)Cl]NO3, may enhance the cytotoxic activity of such complexes. Show less

Abstract Five coordination compounds [Cu2(Bipy)2L4]·C2H5OH (Iа, Ib), [Cu2(Dmbipy)2L4] (II), [Cu2(Phen)2L4]·H2O (IIIa), [Cu2(Dmphen)2L4] (IVa), and [Cu2(Phendione’)2L4]·2C2H5OH·2H2O (V) are synthesized from 5-(4-chlorophenyl)-1H-tetrazole (HL), where Bipy is 2,2'-bipyridine, Dmbipy is 4,4'-dimethyl-2,2'-bipyridine, Phen is 1,10-phenanthroline, Dmphen is 4,7-dimethyl-1,10-phenanthroline, and Phendione’ is 6-ethoxy-6-hydroxy-1,10-phenanthrolin-5-one. The crystal structures of the complexes are determined by X-ray diffraction (XRD) of single crystals (CIF files CCDC nos. 2225368 (Ia), 2225369 (Ib), 2225370 (II), 2225372 (IIIa), 2225373 (IVa), and 2225371 (V)). The compounds are binuclear due to the bridging function of the tetrazolate anion, and the coordination number of copper is five in all synthesized complexes. The cytotoxic activity of the complexes against the Hep2 and HepG2 cancer cell lines and non-cancerous human fibroblasts MRC-5 is studied. The complexes exhibit pronounced cytotoxic properties, and compound V has the maximum selectivity index with respect to the cancer cells. Show less

Abstract The complex [Zn(Phen)(H2O)L2] (I), where HL is 5-benzyltetrazole, Phen is 1,10-phenanthroline, was synthesized. The compound was characterized by standard physicochemical methods (elemental analysis, powder X-ray diffraction, IR spectroscopy). According to X-ray diffraction data (CCDC no. 2220597), zinc coordination environment in the crystal structure of I corresponds to a distorted trigonal bipyramid. The ligand HL is monodentate and is coordinated via tetrazolate ring nitrogen. The stability of complex I was studied by NMR spectroscopy in DMSO. The cytotoxic properties of the compound were assessed against HepG-2 (hepatocellular carcinoma) and MRC-5 (noncancerous human fibroblasts) cells. Complex I exhibits weak cytotoxic properties in the studied concentration range (1–100 µM). Show less

The exploration of ruthenium complexes as anticancer drugs has been the focus of intense investigation. In this study, we synthesized and characterized four C,N-cyclometalated ruthenium(II) complexes (Ru1–Ru4) coordinated with pyridine-functionalized N-heterocyclic carbene (NHC) and auxiliary ligands (e.g., acetonitrile, 1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthroline, and 4,7-diphenyl-1,10-phenanthroline). X-ray diffraction analysis showed that all of the four cycloruthenated complexes are hexa-coordinated in a typical octahedral geometry. In vitro cytotoxic studies revealed that cyclometalated Ru-NHC complexes Ru3 and Ru4 had stronger anticancer activity than their corresponding Ru-NHC precursor Ru1 and the clinically used cisplatin. For HeLa cells, Ru3 and Ru4 exhibited potent cytotoxicity with the IC50 value of 4.31 ± 0.42 μM and 3.14 ± 0.23 μM, respectively, which was approximately three times lower than that of cisplatin. More interestingly, Ru3 and Ru4 not only effectively inhibited the proliferation of HeLa cells, but also exhibited potential anti-migration activity. In the scratch wound healing assay, Ru3 and Ru4 treatment significantly reduced the wound healing rate of HUVEC cells. Mechanistic studies showed that Ru3 and Ru4 caused a dual action mode of mitochondrial membrane depolarization and endoplasmic reticulum stress and finally induced apoptosis of HeLa cells. Show less

Herein, we present the synthesis, characterization, and in vitro investigation of cytotoxic activity against cancer (HepG-2, MCF-7) and non-cancerous (Hek-293, MRC-5) cell lines of six copper(II) complexes with 1H-tetrazole-5-acetic acid (H2L) and secondary ligands, such as olygopyridines (dmphen – 4,7-dimethyl-1,10-phenanthroline, phendione – 1,10 phenanthroline-5,6-dione, 5-Cl-phen – 5-chloro-1,10-phenanthroline, phen – 1,10 phenanthroline, dmbipy – 2,2′-bi-4-picoline, bipy – 2,2′-bipyridine). These compounds were characterized by powder X-ray diffraction, IR spectroscopy, elemental, and thermogravimetric analysis. The behavior of the complexes in solution was studied by optical spectroscopy, conductometry, and EPR. The DNA binding constant has been obtained for complex 5 using UV–vis spectroscopy. The antimicrobial activity of the complexes has been investigated against E. coli, S. aureus, P. italicum, and C. steinii. In addition, eight new crystal structures were obtained: [Cu(5-Cl-phen)L]n·0.5DMSO·1.5H2O (3a), [Cu(phen)L]n·2.5nH2O (4·2.5nH2O), [Cu3(phen)2(H2O)(HL)2L2]n·6nH2O (4a), [Cu(dmbipy)L]n (5), [Cu(dmbipy)(HL)2] (5a), [Cu3(dmpiby)2(HL)2L2]n·2nH2O·2nC2H5OH (5b), [Cu(bipy)L]n (6), and [Cu(bipy)(H2O)L] (6a). Show less

We describe the synthesis of a triazolyl-pyridine-based aminophosphine, N-(diphenylphosphaneyl)-6-(1-phenyl)-1H-(1,2,3-triazol-4-yl)pyridine-2-amine [2,6-{(PPh2)-N(H)(C5H3N)(C2HN3C6H5)}] [1, PN(H)N hereafter], and its palladium and platinum complexes and their catalytic application. The reaction of 1 with [M(COD)Cl2] (M = Pd or Pt) afforded the cationic complex [(MCl){PN(H)N}-κ3-P,N,N]Cl [M = Pd (2) or Pt (3)]. Alternatively, compounds 2 and 3 were also synthesized by treating [2,6-{H2N(C5H3N)(C2HN3C6H5)}] (A) with [M(COD)Cl2] (M = Pd or Pt), followed by the addition of stoichiometric amounts of PPh2Cl and Et3N. The neutral, dearomatized complexes [(MCl){PNN}-κ3-P,N,N] [M = Pd (4) or Pt (5)] were prepared by the deprotonation of the NH of 2 and 3 with 1 equiv of tBuOK. Compounds 4 and 5 were also synthesized stepwise by treating [2,6-{H2N(C5H3N)(C2HN3C6H5)}] (A) with [M(COD)Cl2] (M = Pd or Pt) to give intermediate complexes [{MCl2}2,6-{NH2(C5H3N)(C2HN3C6H5)-κ2-N,N}] [M = Pd (B) or Pt (C)], which were subsequently phosphinated. The in situ-generated PNN ligand-stabilized Pd nanoparticles from compound 2 catalyzed the annulation of o-bromobenzaldehyde with alkynes to yield indenone derivatives. Mechanistic investigations suggested that the reaction was catalyzed by Pd nanoparticles (Pd@2) generated from compound 2 and proceeded through sequential oxidative addition, alkyne insertion, and reductive elimination steps to produce indanone products. Show less

Five coordination compounds [Cu2(Bipy)2L4]·C2H5OH (Iа, Ib), [Cu2(Dmbipy)2L4] (II),[Cu2(Phen)2L4]·H2O (IIIa), [Cu2(Dmphen)2L4] (IVa), and [Cu2(Phendione’)2L4]·2C2H5OH·2H2O (V) aresynthesized from 5-(4-chlorophenyl)-1H-tetrazole (HL), where Bipy is 2,2'-bipyridine, Dmbipy is 4,4'-dimethyl-2,2'-bipyridine, Phen is 1,10-phenanthroline, Dmphen is 4,7-dimethyl-1,10-phenanthroline, andPhendione’ is 6-ethoxy-6-hydroxy-1,10-phenanthrolin-5-one. The crystal structures of the complexes aredetermined by X-ray diffraction (XRD) of single crystals (CIF files CCDC nos. 2225368 (Ia), 2225369 (Ib),2225370 (II), 2225372 (IIIa), 2225373 (IVa), and 2225371 (V)). The compounds are binuclear due to thebridging function of the tetrazolate anion, and the coordination number of copper is five in all synthesizedcomplexes. The cytotoxic activity of the complexes against the Hep2 and HepG2 cancer cell lines and noncanceroushuman fibroblasts MRC-5 is studied. The complexes exhibit pronounced cytotoxic properties, andcompound V has the maximum selectivity index with respect to the cancer cells. Show less

Five coordination compounds [Cu2(Bipy)2L4]·C2H5OH (Iа, Ib), [Cu2(Dmbipy)2L4] (II),[Cu2(Phen)2L4]·H2O (IIIa), [Cu2(Dmphen)2L4] (IVa), and [Cu2(Phendione’)2L4]·2C2H5OH·2H2O (V) aresynthesized from 5-(4-chlorophenyl)-1H-tetrazole (HL), where Bipy is 2,2'-bipyridine, Dmbipy is 4,4'-dimethyl-2,2'-bipyridine, Phen is 1,10-phenanthroline, Dmphen is 4,7-dimethyl-1,10-phenanthroline, andPhendione’ is 6-ethoxy-6-hydroxy-1,10-phenanthrolin-5-one. The crystal structures of the complexes aredetermined by X-ray diffraction (XRD) of single crystals (CIF files CCDC nos. 2225368 (Ia), 2225369 (Ib),2225370 (II), 2225372 (IIIa), 2225373 (IVa), and 2225371 (V)). The compounds are binuclear due to thebridging function of the tetrazolate anion, and the coordination number of copper is five in all synthesizedcomplexes. The cytotoxic activity of the complexes against the Hep2 and HepG2 cancer cell lines and noncanceroushuman fibroblasts MRC-5 is studied. The complexes exhibit pronounced cytotoxic properties, andcompound V has the maximum selectivity index with respect to the cancer cells. Show less

Twelve Re(I) tricarbonyl diimine (2,2′-bipyridine and 1,10-phenanthroline) complexes with thiotetrazolato ligands have been synthesised and fully characterised. Structural characterisation revealed the capacity of the tetrazolato ligand to bind to the Re(I) centre through either the S atom or the N atom with crystallography revealing most complexes being bound to the N atom. However, an example where the Re(I) centre is linked via the S atom has been identified. In solution, the complexes exist as an equilibrating mixture of linkage isomers, as suggested by comparison of their NMR spectra at room temperature and 373 K, as well as 2D exchange spectroscopy. The complexes are photoluminescent in fluid solution at room temperature, with emission either at 625 or 640 nm from the metal-to-ligand charge transfer excited states of triplet multiplicity, which seems to be exclusively dependent on the nature of the diimine ligand. The oxygen-sensitive excited state lifetime decay ranges between 12.5 and 27.5 ns for the complexes bound to 2,2′-bipyrdine, or between 130.6 and 155.2 ns for those bound to 1.10-phenanthroline. Quantum yields were measured within 0.4 and 1.5%. The complexes were incubated with human lung (A549), brain (T98g), and breast (MDA-MB-231) cancer cells, as well as with normal human skin fibroblasts (HFF-1), revealing low to moderate cytotoxicity, which for some compounds exceeded that of a standard anti-cancer drug, cisplatin. Low cytotoxicity combined with significant cellular uptake and photoluminescence properties provides potential for their use as cellular imaging agents. Furthermore, the complexes were assessed in disc diffusion and broth microdilution assays against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), Escherichia coli (E. coli), and Pseudomonas aeruginosa (P. aeruginosa) bacterial strains, which revealed negligible antibacterial activity in the dark or after irradiation. Show less

Here, we report a novel mechanism to selectively degrade target proteins. 3-(3-Phenoxybenzyl)amino-β-carboline (PAC), a tubulin inhibitor, promotes selective degradation of αβ-tubulin heterodimers. Biochemical studies have revealed that PAC specifically denatures tubulin, making it prone to aggregation that predisposes it to ubiquitinylation and then degradation. The degradation is mediated by a single hydrogen bond formed between the pyridine nitrogen of PAC and βGlu198, which is identified as a low-barrier hydrogen bond (LBHB). In contrast, another two tubulin inhibitors that only form normal hydrogen bonds with βGlu198 exhibit no degradation effect. Thus, the LBHB accounts for the degradation. We then screened for compounds capable of forming an LBHB with βGlu198 and demonstrated that BML284, a Wnt signaling activator, also promotes tubulin heterodimer degradation through the LBHB. Our study provided a unique example of LBHB function and identified a novel approach to obtain tubulin degraders. Show less

Two Zn(ii) complexes based on tetrazol were prepared. Nanoparticles of the complexes can inhibit the proliferation of cancer cells in vitro. This work provided a strategy on designing anticancer materials based on coordination complexes. Show less

AbstractThe long‐standing history of platinum coordination complexes in nucleic acid recognition attests to the unique suitability of such species for therapeutic applications. Here, we report the synthetic exploration and development of a family of di‐imine ligands, and their platinum(II) complexes, elaborated on a 3‐(2‐pyridyl)‐[1,2,4]triazolo[4,3‐a]pyridine platform which, in its unsubstituted form, has recently been shown to display exceptional capabilities for guanine quadruplex (G4) targeting. The identification of facile, high‐yielding synthetic methods for the derivatization of this platform for the incorporation of additional sites of interactions with guanine quadruplex loops and grooves, along with the optimization of platinum(II) complexation methods, are discussed. Gratifyingly, preliminary biophysical screening of this novel family of binders validates all but one family members as robust G4 binders and highlights enhanced selectivity for quadruplex versus duplex DNA compared to the parent compound. These results bear promise for practical developments based on this platform. Show less

AbstractWell‐defined copolymers containing luminescent iridium and hybrid iridium/rhenium fragments are prepared utilizing parent poly(n‐butyl acrylamide‐co‐N‐(1H‐tetrazol‐5‐yl) acrylamide) as macromolecular chelating species. The parent (co)polymers are prepared via the modification of a precursor poly(pentafluorophenyl acrylate) (polyPFPA) homopolymer, prepared by reversible addition‐fragmentation chain transfer polymerization, with n‐butylamine and 5‐aminotetrazole. Reaction of the parent copolymers with [Ir2(ppy)4(μ−Cl2)] (ppy = 2‐phenylpyridine) yields modified copolymers containing the Ir(ppy)2 fragment as a pendent group. Attachment of the Ir species is confirmed by a combination of photophysical studies, UV–Vis spectroscopy, and visually under irradiation with UV light. Importantly, it is demonstrated that the chelation of the Ir(ppy)2 fragment to a polymeric scaffold does not impact the fundamental photophysical properties of the Ir species. Attachment of a second luminescent metal species, Re(CO)3(phen) (phen = 1,10‐phenanthroline), gives hybrid materials containing Re(I) and Ir(III). The photophysical properties of these hybrid materials are consistent with the presence of both metal species and indicate the occurrence of energy transfer phenomena from the polymer‐bound Ir to Re metal centers. Finally, it is demonstrated that the Ir modified polymers and the Ir/Re hybrid materials offer potential in tissue imaging applications with scope to tune both luminescent properties and biological specificity as evidenced from preliminary brain tissue staining experiments. Show less

Transition metal coordination complexes have provided cancer treatment with new insights to overcome the limitations of current chemotherapeutic agents. Utilization of bifunctional tetrazole–carboxylate ligands with Zn(II) obtained two self-assembled complexes [Zn(HL1)(bipy)3/2(H2O)]·CH3OH·4(H2O) (1) (H3L1 = 1,3,5-tri(2-carboxymethyltetrazol-5-yl) benzene) and [Zn(L2)2(H2O)2]2·2H2O (2) (HL2 = (5-pyridin-3-yl-tetrazol-2-yl)-acetic acid). The X-ray diffraction results showed that the two complexes displayed a two-dimensional (2D) layer structure and a one-dimensional (1D) layer structure. Nanocoprecipitation with DSPE-PEG-2000 resulted in the formation of complex nanoparticles (NPS) with excellent water dispersion. In vitro CCK-8 assay indicated the two NPs exert high cytotoxicity and sensitivity and a low half-maximum inhibitory concentration (IC50) towards HeLa than HepG2 cells. In addition, the cytotoxicity was also confirmed by live/dead co-stained experiments. The presented experimental results showed the 1 and 2 NPs were capable of inhibiting cell proliferation in vitro and may help design coordination complex-based anticancer candidates for cancer cells. Show less

Abstract As a kind of multifunctional materials with high porosity, tunable pore structure and easy functionalization, coordination complexes have been widely used in various fields. Here, three complexes were prepared by self‐assembly with Co(II) ions using tetrazolylacetic acids as ligands, 2,2′,2′′‐(benzene‐1,3,5‐triyltris(2 H ‐tetrazole‐5,2‐diyl)) triacetic acid (H 3 tzpha), 2‐(5‐(pyrazin‐2‐yl)‐2 H ‐tetrazol‐2‐yl) propanoic acid (Hpztzma) and 2‐(5‐(pyridin‐2‐yl)‐2 H ‐tetrazol‐2‐yl) acetic acid (Hpytza), and were characterized by X‐ray crystallography. These complexes can also self‐assemble into nanoparticles (NPs) in aqueous solution by nanocoprecipitation. In vitro CCK‐8 assay on three kind of human cancer cells (HeLa, HepG2 and Huh7) cells showed these Co(II) complexes have the best cytotoxicity against HeLa cells. And complex 1 had a half maximal inhibitory concentration (IC 50 value) of 14.8 μg mL −1 , which was superior to 16.5 μg mL −1 and 15.2 μg mL −1 of complex 2 and 3 . In addition, the effect of different ligands on cancer cell ablation was explored. The results showed the three NPs can effectively inhibit the proliferation of cancer cells in vitro and provided a strategy on designing highly efficient anticancer materials based on coordination complexes. Show less

Abstract The crystal structure of the Cu(II) binuclear complex with 5-phenyltetrazole and 4,4'-dimethyl-2,2'-bipyridine (dmbipy), [Cu2(dmbipy)2L4], has been determined. The complex crystallizes in a monoclinic space group P21/c. The distorted square-pyramidal environment of Cu(II) atoms is formed by five nitrogen atoms belonging to three 5-phenyltetrazolate anions and one dmbipy molecule. Due to the presence of the intermolecular interactions π···π and C–H···π, the binuclear molecules combine into a supramolecular layered structure. The bonding energy has been calculated in terms of the density functional theory for two models of the [Cu2(dmbipy)2L4] complex with various coordination modes of the bridging 5-phenyltetrazole. Show less

In this study, Ni(II) and Co(II) complexes [Co(H2O)2L2] (1), [Ni(H2O)2L2] (2), [Co(phen)L2] (3), [Ni(phen)L2]·2H2O·EtOH (4·2H2O), and [Ni(phen)2(H2O)L]·L·2H2O (5), where L—4,5-dichloro-isothiazole-3-carboxylate anion and phen—1,10-phenanthroline are reported. All complexes have been characterized by physicochemical and spectroscopic methods. Mass spectrometry and UV–Vis spectroscopy have been used to show the behavior of complexes in ethanol solution and phosphate buffer saline. Crystal structures of mononuclear complexes 1, 4 and 5 have been determined by single-crystal X-ray diffraction. In the structure of 4, mononuclear units have been found to form infinite zigzag chains due to the presence of Cl•••Cl non-covalent interactions which can be regarded as halogen bonding. All complexes have been screened in vitro for their cytotoxic activity against Hep2 cancer cell line. The complexes obtained showed no activity (IC50 > 50 µM) in comparison with structurally related Cu(II) complex [Cu(phen)(H2O)L2] exhibiting dose-dependent toxicity comparable to that of cisplatin (IC50 = 3.06 ± 0.07 µM (Cu(II) complex), IC50 = 9.2 ± 0.5 µM (cisplatin)). DNA binding constants were determined using absorption titration: Cu(II), Ni(II) and Co(II) complexes possessed similar DNA binding efficacy (Kb ~ 104). Show less