Bidentate Fashion Research Articles

Synthesis, characterization, crystal structure, in-vitro cytotoxicity, antibacterial, and antifungal activities of nickel(II) and cobalt(III) complexes with acylthioureas

Two thiourea derivatives 1-pentanoyl-3-methyl-3-(4-chlorophenyl)thiourea (HL1) and 1-(3-fluorobenzoyl)-3,3-diphenyl-thiourea (HL2) and their nickel(II) (1) and cobalt(III) (2) complexes have been prepared. The synthesized compounds have been adequately characterized by spectroscopic techniques including elemental analyses, FT-IR, 1H and 13C NMR, and single crystal diffraction. The FT-IR and 1H NMR studies of complexes reveal the occurrence of ligands in the deprotonated states which are coordinated to metal ions in a bidentate fashion. Moreover, this deprotonation brings carbonyl group to contribute to electronic delocalization in the frame –C(O)NC(S)–. Complexes 1 and 2 are crystallized in monoclinic C2/c and triclinic P-1 space groups, respectively. In-vitro bioactivities of synthesized compounds such as brine shrimp lethality assay, antibacterial screening against Enterobacter aerogenes, Bordetella bronchiseptaca and Salmonella typhimurium strains, and antifungal investigation versus Fusarium solani, Aspergillus fumigatus and Mucor fungal strains have also been evaluated. In general, the antibacterial activities of tested compounds are found significantly higher as compared to their antifungal inhibition and cytotoxic activities.

Quantum-Based Modeling of Dephosphorylation in the Catalytic Site of Serine/Threonine Protein Phosphatase-5 (PPP5C)

Serine/threonine protein phosphatase-5 (PP5; PPP5C) is a member of the phosphoprotein phosphatase (PPP) gene family. The PPP catalytic domains feature a bimetal system (M1/M2), an associated bridge hydroxide (W1(OH−)), an M1-bound water/hydroxide (W2), and a highly conserved core sequence. The PPPs are presumed to share a common mechanism: The seryl/threonyl phosphoryl group of the phosphoprotein coordinates the metal ions, W1(OH−) attacks the central phosphorous atom, rupturing the antipodal phosphoester bond and releasing the phosphate-free protein. Also, a histidine/aspartate tandem is responsible for protonating the exiting seryl/threonyl alkoxide. Here, we employed quantum-based computations on a large section of the PP5 catalytic site. A 33-residue, ONIOM(UB3LYP/6-31G(d):UPM7) model was built to perform computations using methylphosphate dianion as a stand-in substrate for phosphoserine/phosphothreonine. We present a concerted transition state (TS) in which W1(OH−) attacks the phosphate center at the same time that the exiting seryl/threonyl alkoxide is protonated directly by the His304/Asp274 tandem, with W2 assigned as a water molecule: W2(H2O). Arg275, proximal to M1, stabilizes the substrate and TS by binding both the ester oxygen (Oγ) and a phosphoryl oxygen (O1) in a bidentate fashion; in the product state, Tyr451 aids in decoupling Arg275 from O1 of the product phosphate ion. The reaction is exothermic (ΔH = −2.0 kcal/mol), occurs in a single step, and has a low activation barrier (ΔH‡ = +10.0 kcal/mol). Our work is an improvement over an earlier computational study that also found bond rupture and alkoxide protonation to be concerted, but concluded that Arg275 is deprotonated during the reactant and TS stages of the pathway. In that earlier study, the critical electron-withdrawal role that Arg275 plays during the hydroxide attack was not correctly accounted for.

The first structurally characterized sulfonamide derivatized Zn(II)-dipicolylamine complexes with eight membered chelate rings. Synthetic and structural studies

Di(2-picolyl)amine has attracted a great deal of attention as the most popular chelating group in synthesizing biological sensors to detect zinc(II) ions. This study reveals the first structurally characterized zinc complexes of the sulfonamide derivatized di(2-picolyl)amine (dpa) moiety with a rare eight membered chelate ring. The novel synthesized zinc(II) complexes; Zn(N(SO2R1dpa)Cl2 (C1), Zn(N(SO2R2dpa)Cl2 (C2), Zn(N(SO2R3dpa)Cl2 (C3), where R1 = 1-naphthalene, R2 = 2-naphthalene, R3 = 5-(dimethylamino)naphthalene were characterized using single crystal X-ray diffraction analysis, 1H NMR, FTIR, UV–Visible and fluorescence spectroscopy. Structural analysis showed that the complexes possess distorted tetrahedron geometry around the zinc centre and that the zinc metal centre is bound to the two pyridyl nitrogens of the dpa group in a bidentate fashion creating a large eight membered chelate ring. The signal attributed to the methylene group (CH2) in the free ligand spectra remains a singlet in the 1H NMR spectra of the zinc complexes but has shifted more downfield. Spectral studies of the complexes revealed that the complexes are fluorescent at concentrations of 0.1 mM with intense fluorescence peaks (C1: 335 nm, C2: 343 nm and C3: 528–551 nm) and, thus, can be further investigated on their potential to be used as imaging agents or biological sensors.

A novel bidentate ligand containing oxime, hydrazone and indole moieties and its BF2+ bridged transition metal complexes and their efficiency against prostate and breast cancer cells

AbstractIn this study, a novel bidentate ligand containing oxime, hydrazone, and indole moieties and its BF2+‐bridged transition metal complexes [Ni(II), Cu(II), and Co(II)] were synthesized and their cytotoxic activities against prostate and breast cancer cells were investigated. The vic‐dioxime ligand bearing indole–hydrazone side groups was synthesized by reacting antiglyoximehydrazine (GH2) with 3‐methoxy indole. The ligand forms mononuclear complexes with a metal‐to‐ligand ratio of 1:2 with M = Co(II)(H2O)2, Ni(II), and Cu(II). These metal complexes were then reacted with BF3(C2H5)2O to obtain BF2+‐bridged transition metal complexes. The Co(II) complex of the ligand is proposed to be octahedral with water molecules as axial ligands, whereas the Ni(II) and Cu(II) complexes are proposed to be square planar. Spectral studies showed that the ligand bonded to the metal ion in a neutral bidentate fashion through the azomethine nitrogen atom and the imine oxime group. Structural assignments are supported by a combination of 1H nuclear magnetic resonance (NMR), 13C NMR, Fourier‐transform infrared, LC/MS, elemental analyses, and magnetic susceptibility testing. For determining the cytotoxic effects of the novel anticancer products, cancer cells were cultured. The antiproliferative effects were determined using the MCF‐7 breast cancer and PC‐3 prostate cancer cell lines. The antiproliferative effects of the products were analyzed and their apoptotic or necrotic effects were determined with the Hoechst/propidium iodide double staining method in both cancer cell lines. Paclitaxel was used as the positive control (1 μm). The results indicated that the newly synthesized compounds are effective on both cell lines between concentrations of 5 and 40 μm and show their effects by apoptotic mechanisms. Besides, these products were found to be more effective on the MCF‐7 cell line. The cytotoxic efficiency of the newly synthesized products was more than that of paclitaxel (depending on concentration), which is a chemotherapeutic agent used in cancer therapy.

A Ru-bda Complex with a Dangling Carboxylate Group: Synthesis and Electrochemical Properties.

Ruthenium complexes containing the tetradentate 2,2'-bipyridine-6,6'-dicarboxylato (bda2-) equatorial ligand and ortho-subsituted pyridines in the axial position have been prepared and characterized using spectroscopic, crystallographic and electrochemical techniques. Complexes [Ru(Hbda)(DMSO)(pyC)] (1) and [Ru(bda)(DMSO)(pyA)] (2) (where pyC is 2-pyridinecarboxylate, pyA is pyridine-2-ylmethanol and DMSO is dimethyl sulfoxide) have been isolated in moderate to high yields. The solid state structures of (1-H)- and 2 reveal the strong chelate effect of the axial pyridine ligand that coordinates in a bidentate fashion leaving the bda2- equatorial ligand coordinating in a tridentate mode. In solution, compound 2 shows a dynamic equilibrium between different coordination modes of the bda2- and pyA ligands. This phenomenon does not occur for 1 because the carboxylate binds stronger than the labile alcohol in 2. Cyclic voltammetry analysis of 1 reveals a complex behavior with a pH-independent wave at E1/2 = 1.12 V that is tentatively associated with the two-electron RuIV/II couple. In sharp contrast, complex 2 shows a pH-dependent one-electron wave at E1/2 = 0.83 V (pH 1), assigned to the proton-coupled electron transfer process of the RuIII/II couple and a pH-independent wave at E1/2 = 1.06 V assigned to the RuIV/III couple. Compound 2 is used to prepare complex [Ru(bda)(pic)(pyA)] (4). This complex is air sensitive and converts to complex [Ru(bda)(pic)(pyE)] (5) (where pyE is methyl 2-pyridine carboxylate) in the presence of methanol. This oxidation also occurs by applying a positive potential to an aqueous solution of 4, producing the derivative [Ru(bda)(pic)(pyC)] (3). Cyclic voltammetry of 3 shows two pH-independent one-electron oxidation waves at E1/2 = 0.64 V and E1/2 = 1.0 V, corresponding to the RuIII/II and RuIV/III couples, respectively. In addition, a water oxidation catalytic wave appears at Eonset ≈ 1.4 V. Foot-of-the-wave analysis of this catalytic wave based on a water nucleophilic attack accounts for a TOFmax = 0.63-0.74 s-1.

Two new cadmium(II) coordination polymers based on imidazole-containing ligands: synthesis, structural characterization and fluorescence properties.

The judicious selection of suitable ligands is vitally important in the construction of novel metal-organic frameworks (MOFs) with fascinating structures and interesting properties. Recently, imidazole-containing multidentate ligands have received much attention. Two new CdII coordination frameworks, namely, poly[tris{μ-1,4-bis[(1H-imidazol-1-yl)methyl]benzene-κ2N3:N3'}tetrakis(nitrato-κ2O,O')dicadmium], [Cd2(NO3)4(C14H14N4)3]n, (I), and poly[[bis{μ3-1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene-κ3N3:N3':N3''}cadmium] hexafluorosilicate], {[Cd(C18H18N6)2](SiF6)}n, (II), have been synthesized and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. In polymer (I), the 1,4-bis[(1H-imidazol-1-yl)methyl]benzene ligand bridges Cd2+ ions with a distorted seven-coordinated pentagonal bipyramidal geometry, forming a one-dimensional ladder chain, and the nitrate anions coordinate to the Cd2+ ions in a terminal bidentate fashion. In the crystal, adjacent chains are further connected by C-H...O hydrogen bonds to generate a two-dimensional (2D) supramolecular structure. Polymer (II) exhibits a 2D layered structure in which 1,3,5-tris[(1H-imidazol-1-yl)methyl] benzene ligands join Cd2+ centres having a six-coordinated octahedral structure. The layers are connected by hexafluorosilicate anions via C-H...F hydrogen-bond interactions, giving rise to a three-dimensional supramolecular network structure in the solid state. In addition, powder X-ray diffraction (PXRD) patterns were recorded, thermogravimetric analyses (TGA) carried out and fluorescence properties investigated.

Preparation of Cr2O3, MnO2, Fe2O3, NiO, CuO, and ZnO oxides using their glycine complexes as precursors for in situ thermal decomposition

GLYCINE (Gly) complexes play an important role in human life. Zn(II), Cu(II), Ni(II), Fe(III), Mn(II), and Cr(III) complexes were synthesized with glycine (Gly). These complexes were characterized by infrared spectroscopy (FT-IR). Based on the stoichiometric data, Gly form a chelate complex in a bidentate fashion at a 1:3 ratio with the trivalent metal ions [Cr(III), Fe(III)] and a 1:2 ratio with the divalent ones [Mn(II), Ni(II), Cu(II) and Zn(II)]. Metal oxides were derived from each of the Gly complexes using thermal decomposition at 800°C. FT-IR analysis of the resulting solids revealed their formation in pure form.

Synthesis and Structure of Trimethylplatinum(IV) Iodide Complex of 4'‐(4‐Methoxyphenyl)‐2,2':6',2''‐terpyridine Ligand and its Halogen Bonding Property

The synthesis and structural characterization of a new trimethylplatinum(IV) iodide complex of 4'‐(4‐methoxyphenyl)‐2,2':6',2''‐terpyridine ligand L, {PtMe3IL} (1) is reported. The X‐ray crystal structure shows that the terpyridine ligand L binds the platinum(IV) metal center in bidentate fashion, which is well supported by the 1H NMR spectrum of 1. The complex 1 upon crystallization with 1,4‐diiodotetrafluorobenzene (DITFB) forms the halogen bonded complex 1a (1·DITFB). The structural investigation shows that 1a exhibits the halogen bonding interaction in which the non‐coordinated pyridyl nitrogen acts as halogen bond acceptors by forming I···N interaction with iodine atom of DITFB. In addition iodine atom of complex 1 also acts as weak halogen bond acceptor.

Synthesis, Characterization, and Application of Segphos Derivative Having Diferrocenylphosphino-Donor Moieties

An axially chiral bisphosphine, Fc-Segphos (1), which possesses diferrocenylphosphino-donor moieties, was prepared as a racemate, and its optical resolution was achieved by the use of chiral HPLC. Ligand 1 coordinated to a palladium(II) cation in a bidentate fashion to construct a unique chiral environment at the palladium center due to the sterically demanding ferrocenyl groups. Ligand (R)-1 was applied in the palladium-catalyzed asymmetric synthesis of axially chiral allenes showing good enantioselectivity of up to 92% ee. In general, (R)-1 displayed better enantioselectivity than the parent Segphos in the palladium-catalyzed reaction, and the Pd/(R)-1 species showed up to 18% ee enhancement over the (R)-Segphos-derived palladium catalyst.

The NpV and PuV Carbonate Systems: Thermodynamics and Coordination Chemistry

New stability constants for NpV and PuV carbonates have been established by coupling capillary electrophoresis (CE) and ICP‐MS at the ionic strength of 0.202 mol/kgwater in NaClO4 and at various temperatures. The thermodynamic data [variation of the molar enthalpy, ΔrHm(T°) and entropy, ΔrSm(T) of reaction] associated with the formation of the AnO2CO3– (An = Np, Pu), AnO2(CO3)23–, and AnO2(CO4)35– complexes were determined. A drastic decrease in molar entropy was observed between the second and third complexes, suggesting important structural changes. Ab initio molecular dynamics showed that the 1:3 complex is formed with two carbonate ligands located at a shorter distance and one at a longer distance, suggesting that the closer ligands are coordinated in a bidentate fashion to the plutonyl(V) moiety whereas the third ligand is monodentate. The variation of the electrophoretic mobilities as function of charge/size ratio confirms unambiguously that the triscarbonate complex of pentavalent plutonium structurally differs from that of hexavalent plutonium where all carbonates anions are bidentate.

Balancing connectivity with function in silver(i) networks of pyridyltriazole (tzpa) ligands results in the formation of a metallogel.

A new flexible and divergent 1,2,3-triazol-4-yl-picolinamide (tzpa) ligand 2 and the half-equivalent model ligand 1, both functionalised with pendant 3-pyridyl groups, are reported and their coordination behaviour with silver(i) ions is explored, both in the crystalline phase and through the formation of a supramolecular metallogel. The self-assembly of tzpa ligand 1 with AgCF3SO3 resulted in the formation of a 1D coordination polymer, binding in a bidentate fashion through the pyridyl and triazole nitrogen atoms of the tzpa binding site and a pendant pyridyl nitrogen atom of an adjacent ligand. Doubling the number of metal binding sites in ligand 2, while retaining the same metal binding domain, gives rise to the formation of a supramolecular metallogel on reaction with AgBF4 at 5 wt% in MeCN, possessing self-healing properties.

Unraveling the solvation geometries of the lanthanum(III) bistriflimide salt in ionic liquid/acetonitrile mixtures.

A synergic approach combining molecular dynamics (MD) and X-ray absorption spectroscopy (XAS) has been used to investigate the structural properties of the La(Tf2N)3 salt (where Tf2N = bistriflimide or bis(trifluoromethansulfonyl)imide) dissolved into several mixtures of acetonitrile and the 1,8-bis(3-methylimidazolium-1-yl)octane bistriflimide (C8(mim)2(Tf2N)2) ionic liquid (IL), with the IL molar fraction (χIL) ranging from 0 to 1. The XAS and MD results show that major changes take place in the La3+ first solvation shell when moving from pure acetonitrile to pure C8(mim)2(Tf2N)2. With increasing the IL concentration of the mixture, the La3+ first shell complex progressively loses acetonitrile molecules to accommodate more and more oxygen atoms of the Tf2N- anions. Except in pure C8(mim)2(Tf2N)2, La3+ is always able to coordinate both acetonitrile and Tf2N- anions, with a ratio between the two different ligands strongly dependent on the IL content. Moreover, the La3+ ion prefers to form a 10-coordinated first shell complex in all the investigated systems, with a slightly different geometry of the cluster depending on the composition of the La3+ first solvation shell. In particular, when moving from pure acetonitrile to pure C8(mim)2(Tf2N)2, the La3+ first solvation shell passes from a bicapped square antiprism geometry where all the Tf2N- anions act only as monodentate ligands, to a "1 + 5 + 4" structure in which the Tf2N- anion binds La3+ both in a monodentate and bidentate fashion. The great adaptability shown by the La3+ solvation structure allows it to reach the optimal balance among many different forces at play involving all of the different species present in the mixtures.

Cytotoxic and apoptotic effects of ternary silver(i) complexes bearing 2-formylpyridine thiosemicarbazones and 1,10-phenanthroline.

New silver(i) compounds containing 2-formylpyridine-N(4)-R-thiosemicarbazones and 1,10-phenanthroline (phen) were synthesized and characterized by spectroscopic techniques (IR and NMR), elemental analysis, ESI-MS and molar conductance measurements. In these complexes, both phen and thiosemicarbazone ligands are coordinated in a chelating bidentate fashion. Compounds 1-3 not only showed good in vitro antiproliferative activity against human lung (A549) and breast tumor cells (MDA-MB-231 and MCF-7), with IC50 values ranging from 1.49 to 20.90 μM, but were also demonstrated to be less toxic towards human breast non-tumor cells (MCF-10A). Cellular uptake studies indicated that compounds 1-3 were taken up by the MDA-MB-231 cells in 6 hours. Cell death assays in the MDA-MB-231 cells were conducted with compound 1 aiming to evaluate its effects on cell morphology, induction of apoptosis, the cell cycle, reactive oxygen species (ROS) formation and mitochondrial membrane potential (Δψm). Compound 1 caused morphological changes, such as cell shrinkage and rounding, increased the sub-G1 phase population, and induced apoptotic cell death, ROS formation and loss of mitochondrial membrane potential (Δψm). DNA binding results revealed that 1 interacted with the ct-DNA minor groove. Complexes 1-3 also exhibited good in vitro activity against M. tuberculosis H37Rv, with MIC values ranging from 3.37 to 4.65 μM.

INTERACTION OF CIS-Pd(NH3)2Cl2 WITH DIPHOSPHONIC ACIDS IN SOLUTIONS AT PHYSIOLOGICAL CHLORIDE-IONS CONCENTRATION

The complex formation of cis-Pd(NH3)2Cl2 with 1-hydroxyethylidene-1,1-diphosphonic (HEDP, H4L1), 3-amino-1-hydroxypropylidene-1,1-diphosphonic (AHPrDP, H4L2), and 1-aminopropylidene-1,1-diphosphonic (APrDP, H4L3) acids in aqueous solutions with the concentration CKCl=0.15 mol/L, which corresponds to the concentration of chloride ions in the intercellular fluid, has been studied by spectrophotometry and pH potentiometry. The results of studying the interaction between cis-Pd(NH3)2Cl2 and diphosphonic acids have been interpreted taking into account the equilibrium concentration distribution of complexes forming in Pd(NH3)2Cl2 solutions at a chloride ion concentration of 0.15 mol/L. It has been found that when Pd(NH3)2Cl2 is dissolved in 0.15 mol/L KCl, ammonia molecules are substituted by chloride ions and a water molecule in the pH range of 2 – 4 to form chloro-aqua complexes [PdCl4]2- and [PdCl3(H2O)]-.
 In the case of complex formation of Pd(II) chloro-aqua complexes with HEDP and AHPrDP, complexes with [Pd 2OPO3 2Cl] chromophore with bidentate coordination of ligands by two oxygen atoms of phosphonic groups are formed in the acidic pH range. At pH>5, a [Pd(L1)(NH3)2]2- complex (lgβ=30.55(5)) is formed in the cis-Pd(NH3)2Cl2:HEDP=1:1 system, and at pH>6, a [Pd(HL2)(NH3)2]- complex (lgβ=40.29(2)) is formed in the cis-Pd(NH3)2Cl2:AHPrDP=1:1 system. The formation of complexes with [Pd 2OPO3 2Namine] chromophore takes place with the displacement of chloride ions from the coordination sphere of complexes with [Pd 2OPO3 2Cl] chromophore by ammonia molecules.
 In the system cis-Pd(NH3)2Cl2:APrDP=1:1, the ligand is coordinated to Pd(II) in a bidentate fashion by the nitrogen atoms of the amine group and oxygen atoms of the phosphonic group to form a [Pd(H2L3)Cl2]2- complex with [Pd Namine OPO3 2Cl] chromophore in the acidic pH range. When pH is increased to 5 and then to 7, a sequential substitution of chloride ions by ammonia molecules takes place to form a [Pd(HL3)(NH3)Cl]2- complex (lgβ=38,84(4)) with [Pd 2Namine OPO3 Cl] chromophore and a [Pd(HL3)(NH3)2]- complex (lgβ=43,14(2)) and [Pd(L3)(NH3)2]2- complex (lgβ=34.91(2)) with [Pd 3Namine OPO3] chromophore.

Rare‐Earth Amido and Borohydrido Complexes Supported by Tetradentate Amidinate Ligands: Synthesis, Structure, and Catalytic Activity in Polymerization of Cyclic Esters

Amido [ButC(NC6H4‐2‐OMe)2]2LnN(SiMe3)2 (Ln = Y (3), Nd (4)) and borohydrido complexes [ButC(NC6H4‐2‐OMe)2]2LnBH4 (Ln = Y (5), Nd (6)) coordinated by new amidinate ligand bearing two pendant anisolyl groups are synthesized. According to X‐ray analysis in complexes 3 and 4 one amidinate ligand is coordinated to the Ln3+ cation in a bidentate fashion (κ2‐NN), while the second one is tetradentate (κ4‐NNOO). At the same time in borohydrido neodymium complex 6 the amidinate ligands demonstrate κ4‐NNOO and κ3‐NNO coordination modes. Complexes 3–6 proved to be efficient initiators for ring‐opening polymerization of rac‐lactide and allow for achieving quantitative conversion of 500 equivalents of monomer into polymer in 0.3–4.5 h at 25 °C. The polymerization of ε‐caprolactone initiated by 3–6 proceeds much faster under similar conditions.

Sodium, Potassium, and Lithium Complexes of Phenanthroline and Diclofenac: First Report on Anticancer Studies.

Diclofenac or 2-[(2′,6′-dichlorophenyl)amino]phenyl}acetic acid (dcf) is a nonsteroidal anti-inflammatory drug, and 1,10-phenanthroline (phen) is a well-known enzyme inhibitor. In this study, three new alkali metal complexes (1–3) containing both phen and dcf were prepared, and their structures were characterized by a variety of analytical techniques including infrared and UV–vis spectroscopy, 1H NMR and 13C NMR elemental analysis, mass spectrometry, and single-crystal X-ray diffraction analysis. In these complexes, phen binds via a N,N′-chelate pocket, while the monoanionic dcf—ligand remains either uncoordinated (in the case of 1 and 3) or coordinated in a bidentate fashion (in the case of 2). All three complexes crystallize in the triclinic space group P-1. [Na2(phen)2 (H2O)4][dcf]2 (1) is a dinuclear sodium complex, where two crystallographically identical Na+ cations adopt a distorted five-coordinate spherical square-pyramidal geometry, with a [N2O3] donor set. [K2(phen)2(dcf)2(H2O)4] (2) is also a dinuclear complex where the crystallographically unique K+ cation adopts a distorted seven-coordinate geometry comprising a [N2O5] donor set. [Li(phen)(H2O)2][dcf] (3) is a mononuclear lithium complex where the Li+ cation adopts a four-coordinate distorted tetrahedral geometry comprising a [N2O2] donor set. The complexes were evaluated for their anticancer activity against lung and oral cancer cell lines as well as for their antibacterial potential. The prepared complexes displayed very good antibacterial and anticancer activities with an excellent bioavailability.

1,2,3-Triazol-5-ylidene bearing a pyridine auxiliary based bidentate PEPPSI type palladium(II) complex: Synthesis, structure, and application in the direct arylation of pyridine N-oxide

A novel PEPPSI (pyridine enhanced precatalyst preparation stabilization and initiation) type palladium(II) complex has been synthesized and fully characterized by NMR, HR-MS, as well as elemental analysis. The molecular structure was finally confirmed by single crystal X-ray diffraction, and it revealed that the pyridyl-armed 1,2,3-triazole ligand is coordinated to the palladium in bidentate fashion. This air and moisture insensitive complex has proven to be a suitable catalyst for the arylation of pyridine N-oxides and 2-bromopyrroles with a broad functional group tolerance, demonstrating that the robustness and high efficiency of our complex.

Synthesis, spectroscopic characterization and DNA binding studies of Cu(II) complex of Schiff base containing benzothiazole moiety

A Schiff base ligand L has been synthesized by the condensation of thiophene-2-carbaldehyde and 2-amino-6-methylbenzothiazole. It has been characterized by elemental analysis, Infrared (IR), 1H NMR and mass spectrometry. Copper (II) complex, ML2 has been synthesized by the reacting ligand L and Copper (II) acetate in 2:1 molar ratio. The Cu(II) complex was characterized by elemental analysis, molar conductance, electronic spectrum, IR and electronic paramagnetic resonance spectrum. TGA has been done to check the thermal stablity of Cu(II) complex. Spectroscopic studies revealed that ligand L binds with the Cu(II) ion as bidentate fashion. On the basis of spectral studies, a distored octahedral geometry has been assigned for Cu(II) complexof ligand L. The DNA binding studies of Cu(II) complex ML2 have been investigated by UV-vis absorption and fluorescence spectroscopy. The binding mode of ML2 with CT-DNA could be assigned as intercalation of the metal complex between DNA base pairs.

C–Hortho⋯Pd interactions in palladium complexes derived from tetrasulfur-difluorinated ligands. Experimental, computational and catalytic studies

The symmetric ligands [Ar-S-CH2-Ph-S-(CH2)-]2, L1 (Ar = o-FPh) and L2 (Ar = p-FPh), and their PdII complexes (1 and 2) were synthesized and structurally characterized. Molecular structures of complexes 1 and 2 display the L1 and L2 ligands coordinating palladium in a κ2-SS bidentate fashion. The metal center exhibits a square planar geometry involving the two sulfur atoms and two chloride atoms which are oriented in cis disposition. Interestingly, the two ortho-hydrogen atoms from the phenyl rings in both complexes are engaged in Pd⋯Hortho interactions with distances from 2.976 to 3.280 Å. These distances can suffer an increase or decrease in their longitude due to the presence of intramolecular C–H⋯π interactions. Additionally, the presence of Pd⋯H interactions in palladium complexes (1 and 2) were identified by an NCI analysis. The complexes 1, 2 and a similar complex 3 that also displays Pd⋯Hortho interactions have been evaluated in the Suzuki-Miyaura cross-coupling reactions.

Interactions of phosphorylated cyclohexapeptides with uranyl: insights from experiments and theoretical calculations

Two phosphorylated cyclohexapeptides (CPs) bearing one (CP1) or two phosphates (CP2) were synthesized to explore the interactions between uranyl ions and very small cyclic peptides. According to the results of the ESI–MS and fluorescence titrations, the 1:1 uranyl-CPs complexes are the main products with the affinity constants of 7.3 × 104 and 2.0 × 105 for CP1 and CP2, respectively. Density functional theory calculations indicate phosphoryl and carboxyl groups coordinate uranyl in mono-dentate and bi-dentate fashions due to steric effects, which is consistent with the results of extended X-ray absorption fine structure spectroscopy.