Search

Nickel(ii)-salen or nickel(ii)-salphen catalyzed alpha-alkylation of ketones and nitriles with primary alcohols is reported. Various alpha-alkylated ketones and nitriles were obtained in high yields through a borrowing hydrogen strategy by using 1-3 mol% of nickel catalyst and a catalytic amount of NaOH (5-10 mol%) under aerobic conditions., TUBITAK [2211/C]; Council of Higher Education [YOK 100/2000], S. Genc and B. Arslan thank TUBITAK (2211/C) and the Council of Higher Education (YOK 100/2000) for their Ph.D. scholarship. The authors also thank the Ege University Directorate of Library and Documentation, EGE-PIK and Enago for providing editing service.

Threading intercalators bind DNA with high affinities. Here, we describe single‐molecule studies on a cell‐permeant luminescent dinuclear ruthenium(II) complex that has been previously shown to thread only into short, unstable duplex structures. Using optical tweezers and confocal microscopy, we show that this complex threads and locks into force‐extended duplex DNA in a two‐step mechanism. Detailed kinetic studies reveal that an individual stereoisomer of the complex exhibits the highest binding affinity reported for such a mono‐intercalator. This stereoisomer better preserves the biophysical properties of DNA than the widely used SYTOX Orange. Interestingly, threading into torsionally constrained DNA decreases dramatically, but is rescued on negatively supercoiled DNA. Given the “light‐switch” properties of this complex on binding DNA, it can be readily used as a long‐lived luminescent label for duplex or negatively supercoiled DNA through a unique “load‐and‐lock” protocol., Using single‐molecule optical tweezers and confocal microscopy we perform kinetic analysis of a novel dinuclear ruthenium(II) DNA imaging probe. Reversable binding is observed on relaxed DNA, however on stretching DNA, threading can occur, resulting in high affinity stable binding. Threading is highly stereoisomer specific and dependent on DNA supercoiling state. This DNA probe has exciting potential for DNA structure specific imaging.

The photophysical properties, especially the intersystem crossing (ISC) of two heavy-atom-free BODIPY derivatives with twisted π-conjugated frameworks (benzo[b]-fused BODIPY, BDP-B; and [a]phenanthrene-fused BODIPY, BDP-P), are studied with steady-state and time-resolved optical and electron paramagnetic resonance (TREPR) spectroscopic methods as well as with ADC(2) theoretical investigations. Interestingly, BDP-B has a planar π-conjugation framework, but it displays weaker UV-vis absorption (ε = 3.8 × 104 M-1 cm-1 at 569 nm) and fluorescence (ΦF < 0.1%), a short-lived singlet-excited state (fluorescence lifetime, τF = 0.2 ns), and a long-lived triplet state (τT = 132.3 μs). In comparison, the more twisted BDP-P shows stronger UV-vis absorption (ε = 9.8 × 104 M-1 cm-1 at 640 nm) and fluorescence (ΦF = 70%), longer singlet-excited-state lifetime (τF = 6.4 ns), and shorter triplet-state lifetime (τT = 18.9 μs). In contrast to helicenes (ΦT = ca. 90%), the ISC of BDP-P and BDP-B is nonefficient (ΦT < 23%). The electron spin selectivity of the ISC of the derivatives is different, manifested by the phase pattern of the TREPR spectra as AAEAEE and EEEAAA for BDP-B and BDP-P, respectively. The spatially confined T1 state wave function of the twisted molecule keeps the T1 state energy high (1.44-1.61 eV). A dark S1 state was identified for BDP-B. This work demonstrated that the twisted π-conjugated framework does not necessarily induce efficient ISC and we found a dark singlet state for BODIPY, which is rare. ispartof: JOURNAL OF PHYSICAL CHEMISTRY B vol:125 issue:23 pages:6280-6295 ispartof: location:United States status: published

Curcumin is among phytochemicals with increasing popularity; unfortunately, its therapeutic potential is restricted due to poor water solubility and bioavailability. The current work undertakes the effort to improve the therapeutic potential of curcumin by complexing it with a cell penetrating peptide using copper ions. A mononuclear complex was synthesized from copper(II) acetate and curcumin. Then this complex was conjugated to the cell penetrating peptide, pVEC. The structural characterization of the complexes was achieved using UV-Vis and Fourier transform infrared spectroscopies. Dynamic and electrophoretic light scattering measurements have confirmed the complexation of curcumin with the peptide to form nanoparticles. Both solubility and kinetic stability of curcumin greatly improved upon complex formation with pVEC through copper ions. Then the antibacterial activity of curcumin in the complex was tested. The amount of curcumin in the minimum inhibitory concentration was similar to 30, similar to 8, and similar to 15 fold lower, respectively for Escherichia coli, Bacillus subtilis, and Staphylococcus aureus when complexed with pVEC; however, this improvement was specifically noteworthy for the gram-negative E. coli since the contribution of pVEC in the complex to the observed activity was negligible in this bacterium. With enhanced solubility and stability, metallo curcumin conjugated pVEC complex possesses potential for different therapeutic applications.

As a platinum-containing anticancer drug, cisplatin is the keystone for treating many malignancies. Nephrotoxicity is the main dose-limiting toxicity, and several hydration therapies and supplementary strategies are utilized to reduce cisplatin-induced kidney damage, so the discovery and development of effective and safe antitumor drugs are still on the path of human health. Herein, a new four-coordinated Pt complex [Pt(TSC)Cl] using N(4)-phenyl-2-formylpyridine thiosemicarbazone (HTSC) was synthesized and characterized by single-crystal X-ray diffraction, (HNMR)-H-1, FT-IR, LC/MS and CHN elemental analysis. The Pt(TSC)Cl complex revealed antiproliferative activity against A549, MCF-7 and Caco-2 cell lines with a low micromolar IC50 (200-1.75 mu M). Specifically, the Pt(TSC)Cl complex displayed more selectivity in Caco-2 cells (IC50 = 2.3 mu M) than cisplatin (IC50 = 107 mu M) after 48 h of treatment. Moreover, compared with cisplatin, a known nephrotoxic drug, the Pt(TSC)Cl complex exhibited lower nephrotoxicity against Hek293 normal cells. We also found that the Pt(TSC)Cl complex can effectively prevent cancer cell propagation in sub-G1 and S phases and induce apoptosis (more than 90%). Real time PCR and western analysis demonstrated that the expression pattern of apoptotic genes and proteins is according to the intrinsic apoptosis pathway through the Bax/Bcl-2-Casp9-Casp3/Casp7 axis. Collectively, our findings indicated that the Pt(TSC)Cl complex triggers apoptosis in Caco-2 cell lines, while low nephrotoxicity was shown and may be considered a useful anticancer drug candidate for colorectal cancers for further optimization and growth. The authors were financially supported by the National Institute for Medical Research Development (NIMAD) [Grant Number 964557] for the financial support of this research. The authors also highly appreciate Research Council University of Tabriz and University of Melbourne for X-ray crystallography.

Metal complexes of thiosemicarbazones have been receiving considerable attention in biological applications such as antimicrobial and anticancer therapies. In this work, Co(II), Zn(II) and Mn(II) complexes of 2-hydroxy-5-methoxyacetophenone thiosemicarbazone (HMAT) were synthesized for the first time and characterized by EPR, FT-IR, NMR, UV-Vis spectroscopies, TG/DSC and elemental analysis. X-ray powder diffraction analysis was carried out for Zn(II) complex. HMAT and its Cu(II), Co(II), Zn(II) and Mn(II) complexes were tested as enzyme inhibitory agents. All compounds are effective inhibitor of cytosolic carbonic anhydrase I and II isoforms (hCA I and II) enzymes. IC(50)values of HMAT and its Cu(II), Co(II), Zn(II) and Mn(II) complexes were determined as 93.35, 324.46, 25.67, 1.06 and 22.36 mu M for CA I isozyme and 99.02, 86.64, 57.76, 10.34 and 36.48 mu M for CA II isozyme, respectively. The evaluation of potential cytotoxic effects of the compounds was performed against normal epithelial breast mammary gland CRL-4010, estrogen-positive low metastatic MCF-7 and triple negative highly metastatic MDA-MB-231 breast adenocarcinoma cell lines by MTT assay. The results showed that the tested metal complexes have high cytotoxic effects than their ligand molecule. In particular, the Cu(II) complex displayed preciously high cytotoxic properties different from the others. Given these facts, the Cu(II) complex could be debated as potential chemotherapeutic molecule against drug-resistant breast cancer cells. Minimum inhibitory concentrations of the compounds against the test organisms were also detected for the microbiological analysis., Necmettin Erbakan University Scientific Research Foundation [BAP-161715001], This study was supported by the Necmettin Erbakan University Scientific Research Foundation (BAP-161715001)

Titanium(IV) complexes of amino-tris(phenolate) ligands (LTiX, X = chloride, isopropoxide) together with bis(triphenylphosphine)iminium chloride (PPNCl) are active catalyst systems for the ring-opening copolymerization of carbon dioxide and cyclohexene oxide. They show moderate activity, with turnover frequency values of ∼60 h–1(0.02 mol % of catalyst, 80 °C, 40 bar of CO2) and high selectivity (carbonate linkages >90%), but their absolute performances are lower than those of the most active Ti(IV) catalyst systems. The reactions proceed with linear evolution of polycarbonate (PCHC) molar mass with epoxide conversion, consistent with controlled polymerizations, and evolve bimodal molar mass distributions of PCHC (up toMn= 42 kg mol–1). The stoichiometric reaction between [LTiOiPr] and tetraphenylphosphonium chloride, PPh4Cl, allows isolation of the putative catalytic intermediate [LTi(OiPr)Cl]−, which is characterized using single-crystal X-ray diffraction techniques. The anionic titanium complex [LTi(OR)Cl]−is proposed as a model for the propagating alkoxide intermediates in the catalytic cycle.

A series of chiral and achiral cyclic seleno-and thiourea compounds bearing benzyl groups on N-atoms were prepared from enetetramines and appropriate Group VI elements in good yields. All the synthesized compounds were characterized by elemental analysis, FT-IR, H-1 NMR and C-13 NMR spectroscopy, and the molecular and crystal structures of (R,R)-4b and (R,R)-5b were confirmed by the single-crystal X-ray diffraction method. These assayed for their activities against metabolic enzymes acetylcholinesterase, butyrylcholinesterase, and alpha-glycosidase. These selenourea and thiourea derivatives of chiral and achiral enetetramines effectively inhibit AChE and BChE with IC50 values in the range of 3.32-11.36 and 1.47-9.73 mu M, respectively. Also, these compounds inhibited alpha-glycosidase enzyme with IC50 values varying between 1.37 and 8.53 mu M. The results indicated that all the synthesized compounds exhibited excellent inhibitory activities against mentioned enzymes as compared with standard inhibitors. Representatively, the most potent compound against alpha-glycosidase enzyme, (S,S)-5b, was 12-times more potent than standard inhibitor acarbose; 7b and 8a as most potent compounds against cholinesterase enzymes, were around 5 and 13-times more potent than standard inhibitor tacrine against achethylcholinesterase (AChE) and butyrylcholinesterase (BChE), respectively., Dokuz Eylul University [2010.KB.FEN.13], The authors thank Dokuz Eylul University for the use of the Oxford Rigaku Xcalibur Eos Diffractometer (purchased under University Research Grant No: 2010.KB.FEN.13).

N,N '-bis(aniline)glyoxime (H2L, 1) has been prepared from aniline and (E,E)-dichloroglyoxime (DCGO) or (E,E)-dibromoglyoxime (DBGO). The reaction of N,N '-bis(aniline)glyoxime (H2L, 1) with solution of PtCl2 in dimethylsulfoxide produced brown-colored bis(E,E-dioximato)platinum(II) complex {[(E,E)-Pt(HL)(2)]} (1a) featuring N-chelating ligand. The crystal structure of this complex has been identified by X-ray diffraction on a single-crystal. In vitro assay of proliferation, cell death, DNA-damage and cell uptake activities of 1 and 1a were tested in HCC cell lines, SNU-182 and HUH-7. 1a has an anti-proliferative effect in HCC cells, however, 1 did not. Furthermore, the cellular uptake of 1a was relatively high compared to cisplatin cellular platinum levels. Compatible with proliferation and cellular uptake results, treatment with 1a caused DNA-damage and subsequent apoptosis in both HCC cell lines. Research Fund of the Gebze Technical University (BAP) [2018-A108-72] This work was financially supported by Research Fund of the Gebze Technical University (BAP, Project Number: 2018-A108-72).

Herein, new Cu(II), Ru(II) and Pd(II) complexes including (2E,2'Z)-2,2'-(1,2-phenylenebis(azan-1-yl-1-ylidene)) bis(5-fluoro-2,3dihydropyrimidin-4(1H)-one) Schiff base ligand were synthesized and characterized. Cu(II), Ru (II), and Pd(II) metal complexes were characterized through microanalysis, molar conductivity, magnetic sus-ceptibility, mass spectrometer, FT-IR, 1H-13C NMR, UV-Vis, and thermal analysis. The antioxidant activities of the compounds were compared with the results of 5-fluorouracil (5-FU) by using different methods. The syn-thesized compounds exhibited quite strong activities compared to the parent drug. The cytotoxicity of reference drug 5-FU and the synthesized compounds against human colon cancer cells (Caco-2) and fibroblast cells (L-929) were determined using in vitro MTT assay. In addition, it was investigated whether electroporation (EP) enhanced the anticancer effect of these compounds in the Caco-2 cancer cells. According to the study's findings, the Ru(II) complex showed a low cytotoxic effect (IC50: 100.4 mu M). However, the new ligand and its Cu(II) and Pd (II) complexes showed a better cytotoxic effect in Caco-2 cells than the reference drug 5-FU. The same com-pounds (ligand, Cu(II), and Pd(II) complexes) showed 4-9 times lower cytotoxic effect in L-929 healthy fibroblast cells than in cancerous cells. 5-FU, ligand, Cu(II), and Pd(II) compounds used in combination with EP reduced the viability of Caco-2 cancer cells to 45.09%, 42.46%, 38.04%, and 30.85%, respectively. Therefore, the ligand and its Cu(II) and Pd(II) complexes may be promising anticancer agents, especially when used in combination with EP. Alparslan University Scientific Research Fund in Turkey [BAP-20-FEF-4901-09] This study was financially supported by Mus? Alparslan University Scientific Research Fund in Turkey (BAP-20-FEF-4901-09) . The authors thank the Mus? Alparslan University Central Research Laboratory for the anticancer activities of the compounds.

In the study, by using 5-amino-4-arylazo-3-methyl-1H-pyrazole derivatives and 2-hydroxy-5(phenyldiazenyl) benzaldehyde; eight novel heterocyclic disperse disazo-azomethine dyes were synthesized, their chemical structures were characterized via FT-IR and 1 H NMR studies. Synthesized compounds were also investigated computationally by performing various techniques. In the computational part of the study, geometry optimizations, frequency analyses, frontier molecular orbital (FMO) calculations, molecular electrostatic potential (MEP) map calculations, FT-IR and NMR spectral analyses were performed on the compounds. Additionally, to reveal their potentials against SARS-CoV-2 main protease (SARS-CoV-2 M-pro), acetylcholine esterase (AChE), heat shock protein (HSP90 alpha) and nicotinamide N-methyl transferase (NNMT), molecular docking calculations were also performed on the synthesized compounds. Molecular dynamics (MD) simulations were carried out on the top-scoring ligand-receptor complexes to evaluate the stability of the complexes and the interactions between ligands and receptors in more detail. Results showed that synthesized compounds can interact with all these four receptors effectively and can be promising structures for further studies. (C) 2021 Elsevier B.V. All rights reserved.

Flavonoids are natural products which are known to have biological activity for human health. In this study, new mixed ligand complexes of Ni(II) and Cu(II) were synthesized by using flavonoid (quercetin or naringenin) and heterocyclic imine (2,2':6',2 ''-terpyridine or 2,2'-bipyiridine) ligands. The new complexes are [Ni(narH-1)(terpy)Cl]center dot 4H(2)O (1, nar = naringenin, terpy = 2,2':6',2 ''-terpyridine), [Cu(narH-1)(terpy)Cl]center dot H2O (2), and [Cu(queH-1)(bpy)(O3N)]center dot 1.5H(2)O (3, que = quercetin, bpy = 2,2'-bipyiridine). The structural features of the synthesized mixed ligand complexes were investigated using elemental analysis, thermogravimetric analysis, Fourier transform infrared spectroscopy, magnetic susceptibility and molar conductivity measurements. The resulting data demonstrated an octahedral geometry for Complex 1 and Complex 2 and square pyramidal geometry for Complex 3. Antioxidant capacity and total phenolic content of Complexes 1-3 were measured by the Folin-Ciocalteu and ABTS methods. Anti- proliferative effect of complexes were tested by SRB and ATP assays on MCF-7 (breast cancer), A549 (nonsmall cell lung cancer), PC-3 (prostate cancer) and HeLa (human cervical cancer) cell lines. Apoptosis was identified using by the fluorescence imaging, caspase cleaved cytokeratin-18 and flow cytometry analysis. Complex 2 and 3 had high total phenolic content and antioxidant activity. Complex 2 was found to show selective cytotoxicity through the induction of apoptosis on MCF-7 cells with having a very low IC50 value ( 50 mu M). In conclusion, Complex 2 is a highly promising and novel compound for breast cancer and warrants further animal experiments. (C) 2019 Elsevier B.V. All rights reserved. Research Fund of Bursa Uludag University [OUAP (F)-2014/27] We thank the Research Fund of Bursa Uludag University for the financial support given to the research Project (Project Number OUAP (F)-2014/27). WOS:000487930600079 Q3

Graphic abstract An outbreak of respiratory disorder caused by coronavirus has been named as coronavirus infection 2019 (COVID-19). To find a specific treatment against this disease researchers are at the frontline. To cure COVID-19, favipiravir (FPV) has been reported as an effective drug based on its high recovery rate. Among nanomaterials, fullerene C60 has achieved enormous attention as a drug delivery vehicle due to its good bioavailability and low toxicity. Hence, in this work, we have investigated the potential of metal-doped fullerene as a drug carrier, based on DFT calculations by using M06-2X functional and 6-31G(d) basis set in water media. In this research electronic parameters and adsorption energy of FPV on interaction with metal-doped (Cr, Fe, and Ni) fullerene is studied. The charge transfer between drug and doped fullerene has been studied through electrophilicity indexes. The structural and electronic properties are explored in terms of adsorption energy through frontier molecular orbital (FMO) and density of state (DOS). It is observed that doping of fullerene C60 with Cr, Fe, and Ni metals significantly enhances the drug delivery rate and provides numerous advantages including controlled drug release at specific target sites which minimize the generic collection in vivo and reduce the side effects. Thusly, it is suggested that our designed metal-doped complexes might be efficient candidates as drug delivery materials for COVID-19 infection. Supplementary Information The online version contains supplementary material available at 10.1007/s11696-021-01815-4.

Guanine-rich sequences of DNA are known to readily fold into tetra-stranded helical structures known as G-quadruplexes (G4). Due to their biological relevance, G4s are potential anticancer drug targets and therefore there is significant interest in molecules with high affinity for these structures. Most G4 binders are polyaromatic planar compounds which π-π stack on the G4's guanine tetrad. However, many of these compounds are not very selective since they can also intercalate into duplex DNA. Herein we report a new class of binder based on an octahedral cobalt(III) complex that binds to G4 via a different mode involving hydrogen bonding, electrostatic interactions and π-π stacking. We show that this new compound binds selectivity to G4 over duplex DNA (particularly to the G-rich sequence of the c-myc promoter). This new octahedral complex also has the ability to template the formation of G4 DNA from the unfolded sequence. Finally, we show that upon binding to G4, the complex prevents helicase Pif1-p from unfolding the c-myc G4 structure.

WOS: 000464613300006, Background: Hydrazones, one of the important classes of organic molecules, are pharmaceutical agents comprising -CO-NH-N=CH- group in the structure therefore and exhibiting significant biological activity. Methods: 5-Chloro-N'-[(substituted)methylidene] pyrazine-2-carbohydrazide (3a-g) and their Pd(II) complexes (4a-h) were synthesized and investigated in vitro anticancer activity on A549, Caco2 cancer and normal 3T3 fibroblast cell lines, using the MTT assay. Results: Anticancer activity screening results revealed that some compounds showed remarkable cytotoxic effect. Among them, 5-chloro-N'-[(4-hydroxyphenyl)methylidene] pyrazine-2-carbohydrazide (3c) displayed higher cytotoxic activity against A549 cancer cell line than the reference drug cisplatin. Conclusion: Compound 3c showed high cytotoxic activity against A549 cancer cell line but it showed low cytotoxic effect against normal 3T3 fibroblast cell line. Antiproliferative and antimetastatic effects of 3c were determined by the real-time monitoring of cell proliferative system (RTCA DP). The cell proliferation, metastatic and invasive activities of A549 cells were decreased due to increased concentration of 3c., Marmara University Scientific Research Commission [SAG-C-YLP-191212-0350, SAG-D-100615-0258], This study was supported by Marmara University Scientific Research Commission [Grant SAG-C-YLP-191212-0350 and SAG-D-100615-0258]. We thank Prof. Dr. Ahmet Karadag and Huseyin Akbas for TGA analysis.

Chemical insertion of carbon dioxide into epoxides under ambient conditions has become one of the most important methods for the construction of cyclic organic carbonates. Various active salen, salophen, and phenolate ligand based complexes have been reported for the synthesis of cyclic organic carbonates. Here we demonstrate a series of ONO pincer type cobalt (III) complexes as efficient catalysts for the cycloaddition of carbon dioxide to epoxides in neat conditions at atmospheric pressure with and without co-catalyst. A turnover number of up to 200,000 under atmospheric pressure is achieved. Moreover, the in situ generated complex shows high activity and the catalyst can be reused for at least 11 cycles without any decline in catalytic performance. Catalytic insertion of carbon dioxide into epoxides offers a useful route to cyclic carbonates. Here cobalt(III) ONO pincer complexes are shown to catalyze this reaction at ambient pressure with turnover numbers of up to 200,000.

Chelate-aryl and chelate-chelate stacking interactions of nickel bis(dithiolene) were studied at the CCSD(T)/CBS and DFT levels. The strongest chelate-aryl stacking interaction between nickel bis(dithiolene) and benzene has a CCSD(T)/CBS stacking energy of -5.60 kcal mol-1. The strongest chelate-chelate stacking interactions between two nickel bis(dithiolenes) has a CCSD(T)/CBS stacking energy of -10.34 kcal mol-1. The most stable chelate-aryl stacking has the benzene center above the nickel atom, while the most stable chelate-chelate dithiolene stacking has the chelate center above the nickel atom. Comparison of chelate-aryl stacking interactions of dithiolene and acac-type nickel chelate shows similar strength. However, chelate-chelate stacking is stronger for dithiolene nickel chelate than for acac-type nickel chelate, which has a CCSD(T)/CBS interaction energy of -9.50 kcal mol-1. © 2018 the Owner Societies. Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/2927]

The first examples of (arene)Os(II) curcuminoid derivatives have been prepared and characterized. The neutral complexes [(p-cym)Os(curc)Cl] (1) and [( p-cym)Os(bdcurc)Cl] ( 2), together with the cationic derivatives [( p-cym)Os(curc)(PTA)][SO3CF3] (3) and [( p-cym)Os(bdcurc)(PTA)][SO3CF3] (4) (PTA = 1,3,5-triaza-7-phosphaadamantane) were characterized by NMR spectroscopy and ESI mass spectrometry, and the crystal structure of 1 was determined by X-ray diffraction analysis. The cytotoxicity of the complexes was evaluated in vitro against human ovarian carcinoma cells (A2780 and A2780cisR), as well as against non-tumorous Human Embryonic Kidney cells (HEK293). Binding of the complexes to potential pharmacological targets and serum carriers was also explored.

The geometry and bonding of N-heterocyclic carbenes to metal surfaces depends on the substituents on the N-atoms., N-heterocyclic carbenes (NHCs) bind very strongly to transition metals due to their unique electronic structure featuring a divalent carbon atom with a lone pair in a highly directional sp2-hybridized orbital. As such, they can be assembled into monolayers on metal surfaces that have enhanced stability compared to their thiol-based counterparts. The utility of NHCs to form such robust self-assembled monolayers (SAMs) was only recently recognized and many fundamental questions remain. Here we investigate the structure and geometry of a series of NHCs on Au(111) using high-resolution X-ray photoelectron spectroscopy and density functional theory calculations. We find that the N-substituents on the NHC ring strongly affect the molecule–metal interaction and steer the orientation of molecules in the surface layer. In contrast to previous reports, our experimental and theoretical results provide unequivocal evidence that NHCs with N-methyl substituents bind to undercoordinated adatoms to form flat-lying complexes. In these SAMs, the donor–acceptor interaction between the NHC lone pair and the undercoordinated Au adatom is primarily responsible for the strong bonding of the molecules to the surface. NHCs with bulkier N-substituents prevent the formation of such complexes by forcing the molecules into an upright orientation. Our work provides unique insights into the bonding and geometry of NHC monolayers; more generally, it charts a clear path to manipulating the interaction between NHCs and metal surfaces using traditional coordination chemistry synthetic strategies.

The use of organic dyes to promote organic reactions by photoredox catalysis is continuously expanding and was recently reviewed by Nicewicz. The synthesis of new dyes, their application in flow photoredox reactions, and their use in stereoselective and multicomponent transformations have considerably expanded the repertoire of application of organic dyes in photoredox mediated reactions. The low costs of these dyes, their tailored synthesis and availability in combination with the development of new concepts and careful catalytic cycle design (made possible by the application of fine theoretical investigations and deep understanding) are guiding the widespread application of organic dyes in the metallaphotoredox catalysis area. Developments and recent applications of different metal catalyzed processes mediated by organic dyes are covered by this review. This journal is

1,2-Bis(2'-nitrophenoxy)-3-R-benzenes {R = H (1), CH3 (2) and OCH3 (3)} have been prepared from the S-N-Ar reaction between 1-fluoro-2-nitrobenzene and 3-R-catechol (aromatic diol), and are then reduced to the corresponding diamines 1,2-bis(2'-aminophenoxy)-3-R-benzene {R = H (4), CH3 (5) and OCH3 (6)}, respectively. Reaction of these diamines with 2-hydroxy-1-naphthaldehyde gives tetradentate Schiff base ligands {H2L: R = H (H2L1), CH3 (H2L2) and OCH3 (H2L3)}, respectively. The Schiff base ligands coordinate to metal(II) ions to provide the complexes ML1, ML2 and ML3 (M = Cu and Zn), respectively. X-ray molecular structure determinations were performed to explore stereochemical rigidity as the origin of chirality induction in the dinitro (2), diamine (5) and Schiff base ligands (H2L1 and H2L2) as well as in the complexes (ZnL2, ZnL3 and CuL3), respectively. The structures feature an N2O2-chromophore from bis(2-oxo-1-naphthaldiminate) moieties with one additional weak Cu/Zn center dot center dot center dot O (ether) contact to give a 4 + 1 coordination with a distorted square-pyramidal geometry for ZnL2, ZnL3 and CuL3, respectively. Without considering this additional contact, the structures are distorted tetrahedral or distorted square-planar for the Zn or Cu complexes, such that a chiral Lambda- and Delta-configuration at the metal atom is induced. All three metal complexes crystallize as a crystalline racemate or racemic mixture of Lambda/Delta-ML. The supramolecular packing in the structures is organized by inter-/intra-molecular pi-pi and C-H center dot center dot center dot pi interactions, respectively. The optimized structures and excited state properties from DFT/TDDFT calculations support the experimental results.

Metal ions play an important role in diverse biological processes, and much of the basic knowledge derived from studying native bioinorganic systems are applied in the synthesis of new molecules with the aim of diagnosing and treating diseases. At first glance, metalloproteins and metallodrugs are very different systems, but metal ion coordination, redox chemistry and substrate binding play essential roles in advancing both of these research fields. In this article, we discuss recent metalloprotein and metallodrug studies where electron paramagnetic resonance spectroscopy served as a major tool to gain a better understanding of metal-based structures and their function.

Presented here is a comprehensive study of highly oxidized multiple‐decker complexes composed of TbIII and CdII ions and two to five phthalocyaninato ligands, which are stabilized by electron‐donating n‐butoxy groups. From X‐ray structural analyses, all the complexes become axially compressed upon ligand oxidation, resulting in bowl‐shaped distortions of the ligands. In addition, unusual coexistence of square antiprism and square prism geometries around metal ions was observed in +4e charged species. From paramagnetic 1H NMR studies on the resulting series of triple, quadruple and quintuple‐decker complexes, ligand oxidation leads to a decrease in the magnetic anisotropy, as predicted from theoretical calculations. Unusual paramagnetic shifts were observed in the spectra of the +2e charged quadruple and quintuple‐decker complexes, indicating that those two species are actually unexpected triplet biradicals. Magnetic measurements revealed that the series of complexes show single‐molecule magnet properties, which are controlled by the multi‐step redox induced structural changes., This work was financially supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Numbers JP14J02656 (Y.H.), JP20225003 (M.Y.), JP15K05467 (K.K.), JP24750119 (K.K.), 18K14242 (Y.H.), 19K05401(Y.K), Tohoku University Molecule & Material Synthesis Platform in Nanotechnology Platform Project, CREST, JST JPMJCR12L3 (M.Y.), PhD scholarship from the Beilstein‐Institut zur Förderung der Chemischen Wissenschaften (M.D.), the German‐Japanese University Consortium (HeKKSaGOn), the state of Baden‐Württemberg through bwHPC and the German Research Foundation (DFG) through grant no INST 40/467‐1 FUGG (JUSTUS cluster), European Union (ERC StG 2012–306826 e‐GAMES), Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBER‐BBN), the Spanish Ministry of Economy and Competitiveness (projects FANCY CTQ2016‐80030‐R, MOTHER MAT2016‐80826‐R and the “Severo Ochoa” Programme for Centers of Excellence in R&D, SEV‐2015‐0496), Generalitat de Catalunya (2017SGR918), 111 Project (B18030) from China (M.Y.), the scientific grants R‐143‐000‐A80‐114, R‐143‐000‐A65‐133 from the National University of Singapore. We thank Dr. Norihisa Hoshino for EPR measurements, Dr. Tetsuko Nakaniwa and Prof. Dr. Genji Kurisu and Dr. Takefumi Yoshida for SCXRD measurements. This paper is Contribution No. 62 from the Research Center for Thermal and Entropic Science.

A series of arene Ru(II) salt complexes of the type [(eta(6)-arene)RuCl(eta(2)-dppm)](+)[ECl3](-) (arene = C6H6, p-cymene, 1,3,5-Me3C6H3; E = Ge, Sn) bearing trichlorogermanate and trichlorostannate anions are reported. Starting from the known complexes: [(eta(6)-C6H6)RuCl2(eta(1)-dppm)] (1), [(eta(6)-p-cymene)RuCl2(eta(1)-dppm)] (3) and the novel complex [(eta(6)-1,3,5-Me3C6H3)RuCl2(eta(1)-dppm)] (7) (dppm = 1,1-bis(diphenylphosphino)methane), reactions with SnCl2 or GeCl2(dioxane) respectively afforded, by halide abstraction at the ruthenium(II) centres in 1, 3 or 7 the salts: [(eta(6)-C6H6)RuCl(eta(2)-dppm)](+) SnCl3- (2), [(eta(6)-p-cymene)RuCl(eta(2)-dppm)](+) SnCl3- (4), [(eta(6)-C6H6)RuCl(eta(2)-dppm)](+) GeCl3- (5), [(eta(6)-p-cymene) RuCl(eta(2)-dppm)](+) GeCl3- (6), [(eta(6)-1,3,5-Me3C6H3)RuCl(eta(2)-dppm)](+) SnCl3- (8) and [(eta(6)-1,3,5-Me3C6H3) RuCl(eta(2)-dppm)](+) GeCl3- (9). The trichlorostannate complexes 2, 4 and 8 are extremely rare examples of ruthenium complexes bearing the SnCl3- counter anion, and the complexes 5, 6 and 9 are the first examples of ruthenium trichlorogermanate complexes to be reported. All compounds were isolated in high yields as air stable materials and were spectroscopically characterized by multinuclear NMR: (H-1, P-31 {H-1}, C-13{H-1}), Infra-red (IR), UV-Vis, and high resolution electrospray ionization mass spectrometry (HR-ESI-MS), the latter both in (+) and (-) mode. Additionally, single crystal X-ray diffraction analyses of salts 4 and 6 are reported, revealing pseudotetrahedral Ru(II) centres with eta(6) bound p-cymene ligands and eta(2)-bound dppm ligands with statistical disorder on the ECl3- anions (E = Ge (6), Sn (4)). Density functional theory calculations (B3LYP with the basis set 6-31 + G(d,p) for H, C, P and Cl atoms; while for Ru, Ge, and Sn atoms DGDZVP basis set) are reported for salts 4 and 6 revealing localization of the LUMOs on the ruthenium-arene rings and some localization on the chloride atom. Finally, MTT in vitro cytotoxicity assays for the MCF-7 and MDA-MB-231 breast cancer cell lines are reported for all complexes and compared to cisplatin. All complexes show remarkable in vitro cytotoxic activity and most are considerably more cytotoxic than cisplatin in both breast cancer cell lines: IC50 values range from 2.25 mu M (compound 2) to 5.97 mu M (compound 9) (cisplatin = 5.74 mu M) in MCF-7 cells; 2.20 mu M (compound 2) to 6.39 mu M (compound 5) (cisplatin = 13.98 mu M) in MDA-MB-231. Moreover, when compared to nonmalignant breast epithelial cells (MCF12A), all complexes exhibit promising selectivity indices (SI) with compound 5 having the highest SI in MCF-7 cells at 4.8; and compound 6 at 3.65 in MDA-MB-231, with most of the other compounds also being considerably more selective than cisplatin on both celllines (SI = 2.26 on MCF-7 and 0.93 on MDA-MB-231). A clonogenic assay was conducted for salts 5 and 6 and the results reveal that both compounds inhibited long-term (14 days) survival in both breast cancer cell lines tested indicating these drugs are very promising candidates for pre-clinical studies. (C) 2020 The Authors. Published by Elsevier B.V.

Three novel gold(III) complexes with bidentate di(N-heterocyclic carbene) (diNHC) ligands of the general formula [AuL2](PF6)3 (L = diNHC) were isolated by transmetalation of the carbene ligand from the corresponding silver(I) complexes [Ag2L2](PF6)2 to KAuBr4 in the presence of AgPF6. In this regard, the scope of the stereo-electronic properties of the ligand has been investigated. Over a number of seven tested ligands, three ligands led to the formation of the desired gold(III) complex, whereas in the other cases a gold(I) complex of the formula [Au2L2](PF6)2 was isolated as the main product. The anion sensing ability of the prepared gold(III) complexes towards the halides Cl−, Br− and I− has been studied in DMSO-d6 and D2O by means of 1H-NMR titration experiments and in one case also by UV-vis. Replacement of a methyl with a n-butyl wingtip substituent on the imidazole ring strongly favours the interaction with the larger iodide anion with respect to chloride. Introduction of an OH group in the bridge gives rise to metal- and ligand-centred interactions, which allow discrimination of the nature of the involved anion. The formation of the gold(III) complex-halide aggregates has been also analysed with X-ray crystallography studies.

International audience; The utilization of photodynamic therapy (PDT) for the treatment of various types of cancer has gained increasing attention over the last decades. Despite the clinical success of approved photosensitizers (PSs), their application is sometimes limited due to poor water solubility, aggregation, photo-degradation, and slow clearance from the body. To overcome these drawbacks, research efforts are devoted toward the development of metal complexes and especially Ru(II) polypyridine complexes based on their attractive photophysical and biological properties. Despite the recent research developments, the vast majority of complexes utilize blue or UV-A light to obtain a PDT effect, limiting the penetration depth inside tissues and, therefore, the possibility to treat deep-seated or large tumors. To circumvent these drawbacks, we present the first example of a DFT guided search for efficient PDT PSs with a substantial spectral red shift toward the biological spectral window. Thanks to this design, we have unveiled a Ru(II) polypyridine complex that causes phototoxicity in the very low micromolar to nanomolar range at clinically relevant 595 nm, in monolayer cells as well as in 3D multicellular tumor spheroids.

OLED technology beyond small or expensive devices requires light-emitters, luminophores, based on earth-abundant elements. Understanding and experimental verification of charge transfer in luminophores are needed for this development. An organometallic multicore Cu complex comprising Cu–C and Cu–P bonds represents an underexplored type of luminophore. To investigate the charge transfer and structural rearrangements in this material, we apply complementary pump-probe X-ray techniques: absorption, emission, and scattering including pump-probe measurements at the X-ray free-electron laser SwissFEL. We find that the excitation leads to charge movement from C- and P- coordinated Cu sites and from the phosphorus atoms to phenyl rings; the Cu core slightly rearranges with 0.05 Å increase of the shortest Cu–Cu distance. The use of a Cu cluster bonded to the ligands through C and P atoms is an efficient way to keep structural rigidity of luminophores. Obtained data can be used to verify computational methods for the development of luminophores., Nature Communications, 11 (1), ISSN:2041-1723

Interest in base metal catalysis motivates the development of Cu-based photoredox catalysts for organic synthesis. However, only a few Cu catalysts have been applied in photoredox reactions, the majority of which contain one or two 1,10-phenanthroline ligands. Here we design a 4,6-disubstituted 2,2'-bipyridine ligand for Cu. Two heteroleptic [Cu(NN)(PP)][PF6] complexes, where NN stands for the 2,2'-bipyridine ligand and PP stands for a bisphosphine ligand, have been synthesized and characterized. They exhibit longer excited state lifetimes and higher Cu(I) / Cu(II) potentials compared to the most widely used Cu catalyst, [Cu-(dap)(2)]Cl. The complex with Xantphos as the PP ligand is an efficient catalyst for chlorotrifluoromethylation of terminal alkenes, especially styrenes, which had been challenging substrates for previously reported photoredox reactions. This chlorotrifluoromethylation method enables the convenient introduction of a trifluoromethyl group into organic molecules under mild conditions, which is important for medicinal chemistry.

Reactions of P-chloro-1,3,2-diazaphospha[3]ferrocenophanes with ECl3 (E = Al, Ga) under solvent-free conditions and with Na[Mn(CO)(5)] furnished salts featuring a ferrocenophane-based phosphenium cation and neutral phosphenium complexes, respectively. All products were characterized by spectroscopic studies. Single-crystal X-ray diffraction studies confirmed the ionic nature of the phosphenium tetrachloroaluminate and the structural analogy between the phosphenium complexes and Fischer-type carbene complexes. Distinct deviations in the conformation of the ansa bridge suggest electronic stabilization of the electrophilic phosphorus atom by phosphorus-nitrogen pi interactions in the free cation and by phosphorus-metal pi bonding in the complexes. The observation of short intermolecular contacts in the crystalline phosphenium salt and its chemical behavior toward donor solvents attest to the cation having an unusually high degree of Lewis acidity, which was confirmed by DFT studies and related to the presence of a rather large N-P-N angle. Computational studies indicate further that the free phosphenium cation exhibits a closed-shell electronic structure with a formal Fe(II) oxidation state and is thus a true analogue to ferrocenophane-based diaminotetrylenes.

International audience; Controlling the electronic coupling between electron donor and acceptor subunits in a dyad is pivotal for the development of novel organic materials, for instance, thermally activated delayed fluorescence (TADF) materials and triplet photosensitizers. Herein, we prepared two compact electron donor/acceptor dyads based on phenothiazine (PTZ) and naphthalimide (NI) with different conformation restrictions induced by the C–N (NI-N-PTZ) or C–C (NI-C-PTZ) linkers. The effect of electronic coupling (matrix elements, VDA) on the photophysical properties, especially the intersystem crossing (ISC) and the TADF, were investigated. NI-C-PTZ shows stronger ground-state electronic coupling (VDA = 2548 cm–1) compared to NI-N-PTZ (VDA = 870 cm–1). TADF was observed only for NI-N-PTZ due to its smaller electronic coupling. Time-resolved electron paramagnetic resonance (TREPR) spectroscopy indicated the presence two triplet excited states and three ISC mechanisms in NI-N-PTZ with different electron spin polarizations (ESP): radical pair ISC (RP-ISC) and spin–orbital charge transfer ISC (SOCT-ISC) for one triplet state, and spin–orbital coupling ISC (SO-ISC) for another. Moreover, for the second one, an inversion of the electron spin polarization (ESP) was observed at 0.5–1.1 μs delay time. NI-N-PTZ represents a rare example for compact electron donor/acceptor dyad showing TADF emission in the red spectral region.

Protic NHC iridium complexes, obtained from the corresponding azido-phenylene-isocyanide precursor complexes, were investigated for ligand-based reactivity. Under redox-neutral conditions, acetonitrile inserts into the N-H bonds to provide kappa(2)-NHC-imidoyl ligand-based complexes, while under reductive conditions the complex also expels one N-H proton to provide the corresponding deprotonated analogues. Using zinc as a reductor activates the NHC-iridium complex to form an asymmetric bimetallic iridium hydrido complex, in which two anionic N-deprotonated NHCs bridge the bimetallic core. X-ray crystal structures are reported for the azido-phenylene-isocyanide precursor complex, the protic NHC complex, and the asymmetric bimetallic iridium hydride complex. Density functional computations and a QTAIM analysis of the bimetallic iridium hydrido complex are provided.

Five new Au-III-peptidodithiocarbamato complexes of the type [(AuBr2)-Br-III(dtc-AA(1)-AA(2)-OR] (in which AA(1)=N-methylglycine (Sar), l/d-Pro; AA(2)=l/d-Ala, -aminoisobutyric acid (Aib); R=OtBu, triethylene glycol methyl ether), differing with regard to the amino acid sequence and/or the chiral amino acid configuration, were designed to enhance tumor selectivity and bioavailability. The gold(III)-based moiety was functionalized to exploit the targeting properties of the peptidomimetic ligand toward two peptide transporters (namely PEPT1 and PEPT2), which are upregulated in several tumor cells. The compounds were synthesized and fully characterized, mainly by means of elemental analysis, one- and two-dimensional NMR spectroscopy, FT-IR, and UV/Vis spectrophotometry. The crystal structures of three compounds were also solved by X-ray diffraction. In vitro cytotoxicity studies using a panel of human tumor cell lines (A549 [non-small-cell lung carcinoma], MCF-7 [breast cancer], A2780 [ovarian carcinoma], H1975 [non-small-cell lung carcinoma], H460 [large-cell lung carcinoma], and A431 [human epidermoid carcinoma]) showed the dtc-Pro-Aib-OtBu derivative to be very effective, with GI(50) values much lower than those of cisplatin. This complex was thus selected for evaluating stability under physiological conditions and possible interactions with serum albumin, as well in PARP-1 enzyme inhibition assays and preliminary ex vivo toxicity experiments on healthy rat tissues.

The oligomerisation of ethylene with chromium-based catalysts containing asymmetric BIMA (bis(benzimidazole)methylamine) ligands produces linear alpha olefins (LAOs) that follow an alternating distribution. The catalytic activity and the degree of alternation is affected by the different ligands; in particular variations at the backbone of the ligand affect the nature of the distribution. For certain catalysts a deviation from regular alternating behaviour is observed, whereby increased amounts of 1-hexene and 1-octene (up to 29 mol%) are obtained compared to the amount expected from the distribution analysis based on C₁₀–C₃₄ LAOs. This behaviour towards more selective oligomerisation to 1-hexene and 1-octene can be explained by varying probabilities of single and double ethylene insertion. The deviations will depend on the size of the metallacycle and are most pronounced early on during the metallacycle growth.

Two pyrazole-based ligands bearing a pyridine moiety, 3-methyl-1-(pyridin-2-yl)-5-pyrazolone (HLpy), and 3-methyl-1-(pyridin-2-yl)-4-trifluoroacetyl-5-pyrazolone (HQpy,CF3), were prepared and fully characterized in the solid-state and the tautomerism of both ligands in solution was also rationalized by using Density Functional Theory. Neutral ruthenium(II) arene complexes of composition [Ru(arene)(Lpy)Cl] and [Ru(arene)(Qpy,CF3)Cl] [arene = p-cymene (cym) or hexamethylbenzene (hmb)]) were synthesized and characterized by IR, 1H, 13C, 15N and 19F NMR spectroscopy, elemental analysis and ESI mass spectrometry. The structures of complexes [Ru(hmb)(Lpy)Cl] and [Ru(hmb)(Qpy,CF3)Cl] were determined by X-ray crystallography, showing κ2-N,N’-coordination not only for Lpy but also for Qpy,CF3 ligand. DFT studies confirm that κ2O,O’-coordination, generally observed in metal complexes with 4-acyl-5-pyrazolone ligands, is not favored in this case. The cytotoxicity of ligands and complexes was evaluated against human ovarian carcinoma cells (A2780 and A2780cisR, cisplatin sensitive and cisplatin-resistant, respectively), and non-tumorous human embryonic kidney SV40 transformed (HEK293T) cells to reveal essentially equivalent activity in the cisplatin sensitive and cisplatin-resistant ovarian carcinoma cells.

We report here on the synthesis of a series of mono-and dinuclear gold(I) complexes exhibiting sulfonated bis(NHC) ligands and novel hydroxylated mono(NHC) Au(I) compounds, which were also examined for their 'biological activities. Initial cell viability assays show strong antiproliferative activities of the hydroxylated mono(NHC) gold compounds (8 > 9 > 10) against 2008 human ovarian cancer cells even after 1 h incubation. In order to gain insight into the mechanism of biological action of the gold compounds, their effect on the pivotal cellular target seleno-enzyme thioredoxin reductase (TrxR), involved in the maintenance of intracellular redox balance, was investigated in depth. The compounds' inhibitory effects on TrxR and glutathione reductase (GR) were studied comparatively, using either the pure proteins or cancer cell extracts. The results show a strong and selective inhibitory effect of TrxR, specifically for the hydroxylfunctionalized NHC gold(I) complexes (8-10). Valuable information on the gold compounds' molecular reactivity with TrxR was gained using the BIAM (biotin-conjugated iodoacetamide) assay and performing competition experiments by mass spectrometry (MS). In good agreement, both techniques suggest the binding affinity of the mono(NHC) Au(I) complexes toward selenols and thiols. Notably, for the first time, bis-carbene formation from mono-carbenes in buffered solution could be observed by MS, which may provide new insights into the speciation mechanisms of bioactive Au(I) NHC complexes. Furthermore, the compounds' interactions with another relevant in cellulo target, namely telomeric G-quadruplex DNA-a higher-order DNA structure playing key roles in telomere function- was investigated by means of FRET melting assays. The lack of interactions with this type of nucleic acid secondary structure support the idea of selective targeting of the hydrophilic Au(I) NHC compounds toward proteins such as TrxR.