Complexes 2c Research Articles

Synthesis, characterization, biological and dielectric studies of a proton transfer compound of pyridine-2,6-dicarboxylic acid with 1H-benzimidazole-2-amine and its vanadium and iron complexes

A proton transfer salt, (HBIA+)(HPDA−)·H2O (L), and its vanadium (HBIA)[VO2(PDA)] (C1) and iron complexes, (HBIA)[Fe(PDA)2]·2H2O (C2) [H2PDA = pyridine-2,6-dicarboxylic acid; BIA = 1H-benzimidazole-2-amine] have been synthesized and characterized by elemental analysis, FT-IR, UV–Visible, 1H and 13C NMR and single crystal X-ray diffraction (SC-XRD) studies. According to SC-XRD, compound L and C2 crystalizes in Monoclinic (P21/c) and C1 in Triclinic (P-1) crystal system and exist as multi-component proton transfer systems stabilized by COO−NH+ ion pair interactions. Thermal, biological and material aspects of compounds were explored by TG-DTA study, antimicrobial, antidiabetic and dielectric study. Antibacterial activity was evaluated against the microorganisms, Escherichia coli (ATCC 25,922), Staphylococcus aureus (ATCC 25,923), Pseudomonas aeroginosa (ATCC 2783), Streptococcus mutans (MTCC 890) and Klebsiella pneumonia (ATCC 13,883). Antifungal activity was evaluated against Aspergillus niger (ATCC16404) and Candida albicans (ATCC 10,231). Band gap energy values with UV–Visible spectra reveal the semiconducting nature of compounds. The vanadium complex shows significant antidiabetic activity (IC50value = 315 µg/mL) compared with the standard reference. Presence of easily polarizable water molecule is responsible for the high dielectric constant value (ԑ = 41.96 at 1 Hz) and ac conductivity (σac) for the iron complex C2.

Tumor-Targeting NHC-Au(I) Complex Induces Immunogenic Cell Death in Hepatocellular Carcinoma.

Immunogenic cell death (ICD) is a promising direction of cancer immunotherapy in hepatocellular carcinoma (HCC). A series of novel NHC-Au(I) complexes derived from 4,5-diarylimidazole, containing glycyrrhetinic acid (GA) as an efficient targeting ligand for HCC, were herein designed and synthesized. Among these, complex 4C exhibited excellent effectiveness for tumor targeting and antitumor activity, which induced the occurrence of ICD in HCC cells. Additionally, 4C can effectively inhibit TrxR enzyme activity, increase reactive oxygen species (ROS) expression, lead to redox homeostasis disorder, mediate mitochondrial dysfunction and endoplasmic reticulum stress (ERS), and cause the characteristic discharge of damage-associated molecular patterns (DAMPs) in HCC cells. More importantly, 4C showed a great ICD-inducing effect in a vaccination mouse model and activated antitumor immunity in a tumor-bearing C57BL/6 mouse model, which is consistent with the in vitro results. In conclusion, we found the potential of Au(I) complex with HCC-targeted capability for effective tumor immunotherapy.

Tumor selective Ru(III) Schiff bases complexes with strong in vitro activity toward cisplatin-resistant MDA-MB-231 breast cancer cells.

Novel ruthenium(III) complexes of general formula Na[RuCl2(L1-3-N,O)2] where L(1-3) denote deprotonated Schiff bases (HL1-HL3) derived from 5-substituted salicyladehyde and alkylamine (propyl- or butylamine) were prepared and characterized based on elemental analysis, mass spectra, infrared, electron spin/paramagnetic resonance (ESR/EPR) spectroscopy, and cyclovoltammetric study. Optimization of five isomers of complex C1 was done by DFT calculation. The interaction of C1-C3 complexes with DNA (Deoxyribonucleic acid) and BSA (Bovine serum albumin) was investigated by electron spectroscopy and fluorescence quenching. The cytotoxic activity of C1-C3 was investigated in a panel of four human cancer cell lines (K562, A549, EA.hy926, MDA-MB-231) and one human non-tumor cell line (MRC-5). Complexes displayed an apparent cytoselective profile, with IC50 values in the low micromolar range from 1.6 ± 0.3 to 23.0 ± 0.1µM. Cisplatin-resistant triple-negative breast cancer cells MDA-MB-231 displayed the highest sensitivity to complexes, with Ru(III) compound containing two chlorides and two deprotonated N-propyl-5-chloro-salicylidenimine (hereinafter C1) as the most potent (IC50 = 1.6µM), and approximately ten times more active than cisplatin (IC50 = 21.9µM). MDA-MB-231 cells treated for 24h with C1 presented with apoptotic morphology, as seen by acridine orange/ethidium bromide staining, while 48h of treatment induced DNA fragmentation, and necrotic changes in cells, as seen by flow cytometry analysis. Drug-accumulation study by inductively coupled plasma mass spectrometry (ICP-MS) demonstrated markedly higher intracellular accumulation of C1 compared with cisplatin.

Electronic Effect on Phenoxide Migration at a Nickel(II) Center Supported by a Tridentate Bis(phosphinophenyl)phosphido Ligand.

A phosphide nickel(II) phenoxide pincer complex (2) reacts with CO(g) to give a pseudo-tetrahedral nickel(0) monocarbonyl complex (3) possessing a phosphinite moiety. This metal-ligand cooperative (MLC) transformation occurs with a (PPP)Ni scaffold (PPP- = P[2-PiPr2-C6H4]2-), which can accommodate both square planar and tetrahedral geometries. The 2-electron reduction of a nickel(II) species induced by CO coordination involves group transfer to generate a P-O bond. For better mechanistic understanding, a series of nickel(II) phenolate complexes (2a-2e, XC6H4O- (X = OMe, Me, H, and CF3) and pentafluorophenolate) were prepared. Kinetic experimental data reveal that a phenolate species with an electron-withdrawing group reacts faster than those with electron-donating groups. The reaction kinetic experiments were conducted in pseudo-first order conditions at room temperature monitored by UV-vis spectroscopy. A pentafluorophenolate nickel(II) complex (2e) reveals instantaneous reactions even at -40 °C to give a nickel(0) monocarbonyl species (3e) and the reverse reaction is also possible. According to kinetic experiments, the rate determining step (RDS) would be the formation of a 5-coordinate intermediate 4 with a negative entropy value (ΔS‡ < 0), and a positive ρ value based on the Hammett plot indicates that the electron-deficient phenolate leads to a faster CO association. Furthermore, scramble experiments suggest that phenolate de-coordinates from the intermediate 4, which gives a (PPP)Ni-CO species 6. The cationic nickel monocarbonyl intermediate can possess a P--Ni(II), P•-Ni(I), or even a P+-Ni(0) character. Such an inner-sphere electron transfer is suggested when a π-acidic ligand such as CO coordinates to a metal ion. Another possible reaction is homolysis of a Ni-O bond to give P--Ni(I) or P•-Ni(0), when a phenoxyl radical is liberated. Considering the P-O bond formation, closed-shell nucleophilic and open-shell radical pathways are suggested. A phenolate pathway reveals a lower energy state for 2e relative to other complexes (2c and 2d), while its radical pathway undergoes via a higher energy state. Therefore, the formation of a P-O bond may occur with the binding of a closed-shell phenolate to the electron-deficient P center.

A Pyridyl-1,2-azaborine Ligand for Phosphorescent Neutral Iridium(III) Complexes

A novel 1,2-azaborine (i.e., 4-methyl-2-(pyridin-2-yl)-2,1-borazaronaphthalene, 1a) has been synthesized and used for the first time as a B-N alternative to common cyclometalating ligands to obtain neutral phosphorescent iridium(III) complexes (i.e., 2a, 3, and 4) of general formula [Ir(C∧N)2(N∧NB)], where C∧N indicates three different cyclometalating ligands (Hppy = 2-phenylpyridine; Hdfppy = 2-(2,4-difluoro-phenyl)pyridine; Hpqu = 2-methyl-3-phenylquinoxaline). Moreover, the azaborine-based complex 2a was compared to the isoelectronic C═C iridium(III) complex 2b, obtained using the corresponding 2-(naphthalen-2-yl)pyridine ligand 1b. Due to the dual cyclometalation mode of such C═C ligand, the isomeric complex 2c was also obtained. All new compounds have been fully characterized by NMR spectroscopy and high-resolution mass spectrometry (MS), and the X-ray structure of 2a was determined. The electronic properties of both ligands and complexes were investigated by electrochemical, density functional theory (DFT), and photophysical methods showing that, compared to the naphthalene analogues, the azaborine ligand induces a larger band gap in the corresponding complexes, resulting in increased redox gap (basically because of the highest occupied molecular orbital (HOMO) stabilization) and blue-shifted emission bands (e.g., λmax = 523 vs 577 nm for 2a vs 2b, in acetonitrile solution at 298 K). On the other hand, the 3LC nature of the emitting state is the same in all complexes and remains centered on the pyridyl-borazaronaphthalene or its C═C pyridyl-naphthalene analogue. As a consequence, the quantum yields of such azaborine-based complexes are comparable to those of the more classical C═C counterparts (e.g., photoluminescence quantum yield (PLQY) = 16 vs 22% for 2a vs 2b, in acetonitrile solution at 298 K) but with enhanced excited-state energy. This proves that such type of azaborine ligands can be effectively used for the development of novel classes of photoactive transition-metal complexes for light-emitting devices or photocatalytic applications.

Spin Crossover Behavior of FeII Complexes Bridged by Thiophene‐Functionalized Triazole Ligands with Different Sizes and Rigidities

AbstractFour thiophene functionalized triazole ligands (L1=4‐(thenyl)‐1,2,4‐triazole, L2=4‐(thiophene ethyl)‐1,2,4‐triazole, L3=N‐Thiophenylidene‐4H‐1,2,4‐triazole‐4‐amine, and L4=(4‐[(E)‐2‐(5‐sulfothiophene)vinyl]‐1,2,4‐triazole) were synthesized. These ligands have different lengths and rigidities, while ligand L4 has a sulfonic acid group that can form a hydrogen bond. Five 1D FeII chain complexes were synthesized: [Fe(L1)3](X)2 ⋅ nH2O [X=BF4−, n=1.5 (C1); X=ClO4−, n=1 (C2)], [Fe(L2)3](BF4)2 ⋅ 1.5H2O (C3); [Fe(L3)3](X)2 ⋅ nH2O [X=BF4−, n=2 (C4); X=ClO4−, n=2.5 (C5)]. The results of temperature‐dependent magnetic susceptibility reveal that complexes C1, C2, and C3 experienced the transition between two spin states. And C4 and C5 maintain high spin states at all temperature ranges. Binuclear complex [Fe2(L3)5(SCN)4] (C6) and mononuclear material [Fe(L4)2(H2O)4] ⋅ 2H2O (C7), these two zero‐dimensional molecules were also synthesized. They all display weak antiferromagnetic exchange coupling and a high spin state in the whole process.

The Transfer Hydrogenation of Cinnamaldehyde Using Homogeneous Cobalt(II) and Nickel(II) (E)-1-(Pyridin-2-yl)-N-(3-(triethoxysilyl)propyl)methanimine and the Complexes Anchored on Fe3O4 Support as Pre-Catalysts: An Experimental and In Silico Approach

The imino pyridine Schiff base cobalt(II) and nickel(II) complexes (C1 and C2) and their functionalised γ-Fe3O4 counterparts (Fe3O4@C1 and Fe3O4@C2) were synthesised and characterised using IR, elemental analysis, and ESI-MS for C1 and C2, and single crystal X-ray diffraction for C1, while the functionalised materials Fe3O4@C1 and Fe3O4@C2 were characterized using IR, XRD, SEM, TEM, EDS, ICP-OES, XPS and TGA. Complexes C1, C2 and the functionalised materials Fe3O4@C1 and Fe3O4@C2 were tested as catalysts for the selective transfer hydrogenation of cinnamaldehyde and all four pre-catalysts showed excellent catalytic activity. Complexes C1 and C2 acted as homogeneous catalysts with high selectivity towards the formation of hydrocinnamaldehyde (88.7% and 92.6%, respectively) while Fe3O4@C1 and Fe3O4@C2 acted as heterogeneous catalysts with high selectivity towards cinnamyl alcohol (89.7% and 87.7%, respectively). Through in silico studies of the adsorption energies, we were able to account for the different products formed using the homogeneous and the heterogeneous catalysts which we attribute to the preferred interaction of the C=C moiety in the substrate with the Ni centre in C2 (-0.79 eV) rather than the C=O (-0.58 eV).

Facet-Dependent Atomic Distances Shape Vanadate Adsorption Complexes on Hematite Nanocrystals.

The environmental fate of vanadate (V(V)) is significantly influenced by iron oxide nanocrystals through adsorption. Nevertheless, the underlying driving force controlling V(V) adsorption on hematite (Fe2O3) facets is poorly understood. Herein, V(V) adsorption on the {001}, {110}, and {214} Fe2O3 facets was explored using batch adsorption experiments, spectroscopic studies, and density functional theory (DFT) calculations. Adsorption experiments suggested that the order of V(V) adsorption capacity followed {001} > {110} > {214}. However, the affinity of V(V) to the {001} facet was the weakest, as evidenced by its least resistance to phosphate and sulfate competition. Our extended X-ray absorption fine structure (EXAFS) study indicated the formation of the inner-sphere monodentate mononuclear (1V) complex on the {001} facet and bidentate corner-sharing (2C) complexes on the {110} and {214} facets. Density functional theory (DFT) calculations showed the 1V complex is preferable when the adjacent Fe-Fe atomic distance is significantly larger than the O-O atomic distance of V(V). Otherwise, the 2C complex is formed if the distance is comparable. This determining factor in surface complex formation can be safely extended to other oxyanions that the compatibility in the atomic distance of Fe-Fe on Fe2O3 facets and O-O in oxyanions shapes the surface complex. The molecular-level understanding of the facet-dependent adsorption mechanism provides the basis for the design and application of oxyanion adsorbents.

Asymmetric transfer hydrogenation of ketones catalyzed by chiral macrocyclic cobalt(II) complexes

Using easily available CoBr2 and chiral cyclic PxNy-type ligands as starting materials, novel chiral cyclic cobalt(II) complexes could be conveniently prepared. Furthermore, we obtained the single crystals suitable for X-ray diffraction to confirm the structures of these cobalt(II) complexes. The asymmetric transfer hydrogenation (ATH) of ketones catalyzed by these well-designed cobalt(II) complexes was investigated. Among them, cobalt(II) complex containing chiral macrocyclic iminophosphine ligand CyP2N4 exhibited high catalytic activity and enantioselectivity (up to 99% ee). Density functional theory (DFT) calculations suggested that cobalt(II) complex (R,R,R',R')-CyP2N4-Co(II) (C1) is easier to form metal hydride, which is the key intermediate during the enantioselective transfer hydrogenation reaction. Study results also revealed that the unique macrocyclic structure of complex C1 could form a special microenvironment around cobalt ion. Therefrom the substrate coordinated with the central metal along this specific reaction channel during the asymmetric catalytic reaction, resulting high enantioselectivity.

Synthesis, Solid State Structure, and Cytotoxic Activity of a Complex Dimer of Yttrium with Anthranilic Acid against Cancer Cells

This paper presents the synthesis and isolation of a new binuclear complex of yttrium with anthranilic acid (HA). The complex [Y2(HA)6(H2O)4] Cl6.2C2H5OH (C1) was obtained as single crystals that its X-ray analysis revealed its triclinic P-1 space group in addition to anti-prismatic geometry around each of the yttrium ions. In the complex, the anthranilic acid ligands are bidentate, zwitter ionic and neutral, and the yttrium ions’ charge is only compensated by six chloride ions. The cytotoxicity of this complex against human breast cancer MDA-MB-231 cells, prostate cancer PC-3 cells, and bladder cancer T-24 cells was evaluated. This yttrium complex displayed more cytotoxic activity against the bladder cancer cells with an IC50 value of 307.7 μg/ml (223 μM). On the other hand, the activities of complex C1 against the MDA-MB-231 and PC-3 cells were less significant respectively with IC50 values of 1097 μg/ml (796 μM) and 921 μg/ml (669 μM).

Effect of substitution on deep-blue Ir(III) N-heterocyclic carbene (NHC) emitters.

The development of Ir(III)-NHC phosphors that display deep-blue luminescence without sacrificing the high photoluminescence quantum yield (PLQY) has become a pivotal area of research. In this respect, two novel deep-blue Ir-NHC emitters (C1 and C2) with strategically designed pro-carbenic imidazolium ligands (L1 and L2) incorporating a heavy bromine atom at the ligand-scaffold were synthesized in good yields (∼80% for L1, L2 and 65% for C1, C2). The ground and excited state properties of the complexes were photophysically determined and the results were found to be in accordance with theoretical calculations at the DFT and TD-DFT levels. Due to the strong σ-donation of the carbene ligands, complexes C1 and C2 displayed oxidation at low anodic potentials. Both the complexes showed deep-blue emission either in solution (λem ∼ 400-425 nm) or as PMMA-doped films of varying concentrations (λem ∼ 400 nm) with an ∼15 times enhanced PLQY with respect to benchmark Ir-NHC complexes. The strategy of incorporating the heavy bromine atom to reduce the molecular vibrations in C1 and C2 was further supported by ∼250 times reduced non-radiative decay constants (knr) and Huang-Rhys constants of C1 and C2 in comparison to those of the benchmark complexes. These facts were also supported by triplet frequency calculations of C1 and C2 to identify the absence of vibrations.

New copper(I) complexes of bulky 5-substituted-2-iminopyrrolyl ligands as catalysts for azide-alkyne cycloaddition.

Five dinuclear copper(I) complexes of the type [Cu{κN,κN'-5-R-NC4H2-2-C(H)N(2,6-iPr2C6H3)}]2 (1a-e; R = 2,4,6-iPr3C6H2 (a), R = 2,6-Me2C6H3 (b), R = 3,5-(CF3)2C6H3 (c), R = 2,6-(OMe)2C6H2 (d), R = CPh3 (e)) were prepared by the reaction of the respective 5-R-2-iminopyrrolyl potassium salts KLa-e and [Cu(NCMe)4]BF4 in moderate yields. These new copper(I) complexes were characterized by NMR spectroscopy, elemental analysis and, in selected cases, by single crystal X-ray diffraction and their structural and electronic features further analyzed by DFT calculations and cyclic voltammetry, respectively. X-ray diffraction studies reveal dimeric Cu structures assembled by 2-iminopyrrolyl bridging ligands adopting a transoid conformation (complexes 1a and 1d), while complexes 1c and 1e displayed a cisoid conformation of those moieties, with respect to the Cu(I) centers. Additionally, VT-1H NMR and 1H-1H NOESY NMR experiments on complexes 1a-e exhibited complex fluxional processes in solution, assigned to a conformational inversion of the respective Cu2N4C4 metallacycles in all complexes but 1c, accompanied by a cisoid-transoid isomerization in the cases of complexes 1d,e. The Cu(I) complexes were also analyzed by cyclic voltammetry, where all complexes exhibit two oxidation processes, where the first oxidation is reversible, with the exception of 1b and 1c, which also show the highest oxidation potentials. The oxidation potentials follow clear trends related to the structural parameters of the complexes, in particular the Cu⋯Cu distance and the Cu2N4C4 macrocycles torsion angles. All new 5-substituted-2-iminopyrrolyl Cu(I) complexes 1a-e served as catalysts for azide-alkyne cycloaddition (CuAAC) reactions, being able to generate the respective 1,2,3-triazole products in yields as high as 82% and turnover frequencies (TOFs) as high as 859 h-1, after optimizing the conditions. The activity, as measured by the TOF, is in accordance with the oxidation potential of the corresponding complexes, the easier the oxidation, the higher the TOF value. Complex 1-H, where R = H, proved to be a poor catalyst for the same reactions, indicating that the 5-substitution in the ligand framework is crucial in stabilizing any potential catalytic species.

Synthesis, characterization, X-ray crystal structure, antioxidant, antimicrobial, and DNA binding interaction studies of novel copper (II)-isoxazole binary complexes

Cu (II) binary complexes of the type [Cu(HLx)2], where x = 1–3, HL1 = 2-((E)-(3,5-dimethylisoxazol-4-ylimino)methyl)-6-methylphenol (C1), HL2 = 2-((E)-(3,5-dimethylisoxazol-4-ylimino)methyl)-6-ethoxyphenol (C2) and HL3 = 2-((E)-(3,5-dimethylisoxazol-4-ylimino)methyl)-4,6-di-tert-butylphenol (C3) have been synthesized and characterized by various analytical, structural, and spectral methods. Single crystal X–ray diffraction analysis of ligand HL1, complexes C2 &C3 revealed that the compounds are crystallized in monoclinic crystal system with the space groups of P1 21/c1 for HL1 &C2, and P1 21/n1 for C3. The antioxidant studies of the synthesized Cu(II) complexes were carried out and it was shown as significant activity against DPPH radical. The synthesized Schiff bases and Cu(II) complexes were explored for antimicrobial activities and the complexes exhibited better potency against diverse microorganisms compared to Schiff bases as ligands. The interaction of Cu(II) complexes with CT–DNA has been explored with absorption and emission spectral techniques and the obtained results were evidence to the intercalative mode of DNA binding. The study of Agarose gel electrophoresis was resulted in three Cu(II) complexes stimulate the double strand breakage of pBR 322 plasmid DNA in the presence and absence of H2O2.

Electro- and photochemical H2 generation by Co(ii) polypyridyl-based catalysts bearing ortho-substituted pyridines.

Cobalt(ii) complexes featuring hexadentate amino-pyridyl ligands have been recently discovered as highly active catalysts for the Hydrogen Evolution Reaction (HER), whose high performance arises from the possibility of assisting proton transfer processes via intramolecular routes involving detached pyridine units. With the aim of gaining insights into such catalytic routes, three new proton reduction catalysts based on amino-polypyridyl ligands are reported, focusing on substitution of the pyridine ortho-position. Specifically, a carboxylate (C2) and two hydroxyl substituted pyridyl moieties (C3, C4) are introduced with the aim of promoting intramolecular proton transfer which possibly enhances the efficiency of the catalysts. Foot-of-the-wave and catalytic Tafel plot analyses have been utilized to benchmark the catalytic performances under electrochemical conditions in acetonitrile using trifluoroacetic acid as the proton source. In this respect, the cobalt complex C3 turns out to be the fastest catalyst in the series, with a maximum turnover frequency (TOF) of 1.6 (±0.5) × 105 s-1, but at the expense of large overpotentials. Mechanistic investigations by means of Density Functional Theory (DFT) suggest a typical ECEC mechanism (i.e. a sequence of reduction - E - and protonation - C - events) for all the catalysts, as previously envisioned for the parent unsubstituted complex C1. Interestingly, in the case of complex C2, the catalytic route is triggered by initial protonation of the carboxylate group resulting in a less common (C)ECEC mechanism. The pivotal role of the hexadentate chelating ligand in providing internal proton relays to assist hydrogen elimination is further confirmed within this novel class of molecular catalysts, thus highlighting the relevance of a flexible polypyridine ligand in the design of efficient cobalt complexes for the HER. Photochemical studies in aqueous solution using [Ru(bpy)3]2+ (where bpy = 2,2'-bipyridine) as the sensitizer and ascorbate as the sacrificial electron donor support the superior performance of C3.

New iron(III) complexes with 2-formylpyridine thiosemicarbazones: Synthetic aspects, structural and spectral analyses and cytotoxicity screening against MCF-7 human cancer cells

2-Formylpyridine thiosemicarbazone - iron (III) chelates [FeL2] Cl•2H2O {L = L1 (C1) [HL1 = 4-(4-Nitrophenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide] and L = L2 (C2) [HL2 = 4-(2,5-Dimethoxyphenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide]} were prepared. The two ligand anions in each complex resulted in saturation of the iron coordination number and consequently the existence of these complexes as 1:1 electrolytes. As well, the iron in these complexes exhibits low-spin electronic configuration. X-ray crystallography of complex C1 indicated its triclinic crystal system and P 1‾ space group. In addition, it proved the ligation through a thiol sulfur atom and two nitrogen atoms of pyridine and azomethine groups. This is while the presence of two water molecules of crystallization in the complex structure was also indicated. The ligand HL1 was selected for cytotoxicity screening against human MCF-7, A-549, HEPG-2 and HCT-116 cancer cells and the most enhanced activities were detected against the breast cells. Against these cells, the compounds HL1, HL2, C1 and C2 induced cytotoxicity, respectively, with IC50 values of 52.4, 145.4, 34.3 and 62.0 μM. However, against the healthy BHK cells, HL1 and HL2 caused cytotoxicity, respectively, with IC50 values of 54.8 and 110.6 μM and cytotoxicity with percent viabilities of 56.7 and 55.4% of the BHK cells by the complexes (137.4 μM of C1 and 131.9 μM of C2) was determined. These activities against MCF-7 cells are less significant compared with the measured value for doxorubicin. But this standard is more toxic to normal cells than the thiosemicarbazones (IC50 (doxorubicin) = 9.66 μM against MCF-7 cells and 36.42 μM against BHK cells).

Novel benzimidazolium salts and their silver(I)-N-heterocyclic carbene complexes: synthesis, characterization and their biological properties

This study was conducted to synthesize and characterize 1,3-dialkyl-5,6-dimethyl-benzimidazolium salts and their silver complexes. Four novel silver(I)-N-heterocyclic carbene complexes were synthesized and characterized by mass analyses, FT-IR and NMR spectroscopy. The biological capacity of the synthesized compounds was evaluated in vitro for their antimicrobial and antitumor activities. The minimum inhibitory concentration (MIC) of the 1,3-dialkyl-5,6-dimethyl-benzimidazolium salts and their complexes was determined for E. coli, P. aeruginosa, S. aureus, C. glabrata and C. albicans in vitro through BMD (Broth Microdilution). The results indicated that silver(I)-NHC complexes exhibit antimicrobial activity. In particular, complex 3c presented a significant broad-spectrum antimicrobial activity. The anticancer properties of the synthesized compounds were evaluated against MCF-7, HCT116, SH-SY5Y and BEAS-2B cell lines. Anticancer activity measurements were carried out according to the Alamar Blue assay. Efficacy was established by comparison of the salts and silver compounds with cisplatin.

A Colorimetric Distinct Color Change Cu(II) 4-{[1-(2,5-dihydroxyphenyl)ethylidene]amino}-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one Chemosensor and its Application as a Paper Test Kit.

In the current research work "4-{[1-(2,5-dihydroxyphenyl)ethylidene]amino}-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one" chemosensor (C1) synthesized by condensation reaction using "4-amino-1,2-dihydro-1,5-dimethyl-2-phenylpyrazol-3-one" and "2,5-dihydroxy actophenone" was used as the effective sensor of metal ion. The C1 shows absorption peak at 326nm due to the C = C bond (π-π*transition), while the absorption peak at 364nm is caused by the C = O bond (n-π*transition). In the presence of copper, C1 only demonstrated a redshift in absorption peak from 364 to 425nm. Even in the presence of other competing metal ions, the hypsochromic shift of the absorption band and the quenching of the fluorescence emission intensity were different for detecting Cu2+, in CH3OH-H2O (v/v = 6:4). The capacity of the C1 to bind with Cu2+ was further proved using DFT simulations. The complex C1 + Cu2+ has a HOMO-LUMO energy gap of 2.8002eV, which is lesser than C1 (2.9991eV) showing improvement in the stability of the C1 + Cu2+ complex. Using the Benesi-Hildebrand and Scatchard plots, calculated Kb values were to be 47,340 and 48369M-1 respectively, showing the creation of stable complexation between Cu2+ and C1 with 1:1 stoichiometry. The limit of detection (LOD) for Cu2+ ion was 649nM. Strip sheets were also built and tested to detect varying amounts of Cu2+ in aqueous solution, and their color change suggested that they might be used for on-site Cu2+ detection in polluted water.

Molecular docking, synthesis and antimicrobial evaluation of metal complexes with Schiff base

The appearance of resistant bacteria was found to reduce the efficiency of antimicrobial therapies with the current antibiotics, thereby increasing the need for more efficient drugs for the treatment of infections. A microbial infection affects tremendously to the human health and antimicrobials are one of the mainly successful forms of chemotherapy which saves the human population from the risk of infectious diseases. In this regard, the present study involves synthesis of transition metal complexes have often shown the immense antimicrobial activity. In this article, metal complexes were synthesized using different metals such as of Zn(II), Hg(II), Pt(II) and Pd(II), using Schiff’s base derived from amino and carbonyl ligand. All the synthesized compounds were characterized using IR, NMR, and mass spectral data and also by UV–visible spectra, molar electric conductance, magnetic susceptibility and thermal studies. Moreover, the antimicrobial activities of metal complexes were demonstrated using both gram negative and gram positive bacteria. The synthetic series of title compounds 6a-d, the compounds 6c and 6d with platinum and palladium metal were found to be active. The complex 6c has shown excellent antimicrobial activity and the result was also confirmed by molecular docking.

Homo- and heteroleptic 3-methylbenzoates of zinc(II) ion based on N-donor heterocycles; structure, DNA binding and pharmacological evaluation

Herein, one homoleptic (C1) and three heteroleptic zinc(II) carboxylates (C2-C4) were synthesized by using 3-methylbenzoic acid (HL) as primary ligand and N- donor heterocycles, i.e., 2,2′-bipyridine (C2), 1,10-phenanthroline (C3) and 2,9-dimethyl-1,10-phenanthroline (C4) as hetero-ligands. The complexes were characterized by multiple techniques that include (1H and 13C) nuclear magnetic resonance (NMR), Fourier Transform infrared (FTIR) spectroscopy and single crystal X-ray diffraction (XRD) analysis. The FTIR spectra of complexes suggested different coordination modes of the carboxylate ligand around the metal center. The single crystal XRD analysis confirmed dinuclear (C2 and C3) complexes having five coordinated zinc centers with distorted square pyramidal geometry, whereas in the mononuclear complex C4, the tetra-coordinated zinc(II) has a distorted tetrahedral geometry that can also be regarded as five coordinated if the bonding of oxygen (O4) lying at the margined distance of Zn-O bond is to be considered. The SS-DNA interaction study has shown enhanced DNA binding affinity for the heteroleptic complexes C2-C4 compared to the free ligand acid HL and homoleptic complex C1. The in vitro antibacterial and antifungal study validated the chelation theory and overtone’s concept. The enzyme inhibition study data revealed a concentration dependent inhibition of the alkaline phosphatase by the synthesized complexes.

Antiparasitic activities of bimetallic N‐heterocyclic carbene gold(I) complexes with ferrocene ligands: Relevance of chlorido and phosphino ligands

Gold(I) complexes carrying imidazole‐2‐ylidene ligands and ferrocene substituents were prepared. Their activities against protozoal Leishmania major and Toxoplasma gondii parasites were analyzed. Certain gold(I) complexes with chlorido and 1,1′‐bis(triphenylphosphino)ferrocene ligands revealed promising antiparasitic effects. The new chlorido complexes 5b and 5c showed high activities against T. gondii tachyzoites and L. major promastigotes while the new ferrocene‐bridged bis‐gold(I) complexes 8a and 8b were particularly active against L. major amastigotes and considerably selective as to toxicity results from Vero cells and macrophages.