Synthesis,characterization, electrochemistry,catalytic, and antimicrobial studies of ruthenium(III) complexes containing ONO donor ligands

A series of ruthenium(III) complexes [RuX(EPh₃)₂L] (where X = Cl or Br; E = P or As; L = deprotonated dibasic tridentate ligand) were prepared by the reaction of [RuX₃(EPh₃)₃] with Schiff bases (H₂L¹–H₂L⁴). The ligands were prepared by the condensation of N-4 phenyl/methyl semicarbazide with o-vanillin/o-hydroxy acetophenone. The complexes were characterized by elemental, physico-chemical, and electrochemical methods. Catalytic studies of these complexes for the oxidation of alcohols and aryl–aryl coupling were carried out. Antimicrobial experiments were also carried out.     

Trigonal (-3) symmetry octahedral lanthanide(III) complexes of zwitterionic tripodal ligands: luminescence and magnetism

Sandwich coordination complexes, [Ln^III(H₃L)₂]X₃?solvents, of Tb(III), Eu(III), Dy(III), Ho(III) and Er(III) were prepared with two new zwitterionic ester-substituted tripodal amine ligands, tris((2-hydroxy-5-n-butyl benzoate)aminoethyl)-amine (H₃L¹) and tris((2-hydroxy-5-methyl benzoate)aminoethyl)-amine (H₃L²). These ligands were synthesised by condensation of the appropriately substituted salicylaldehyde with tris(2-aminoethyl)amine (tren) followed by in situ reduction of the tris-imine to tris-amine. Subsequent 2:1 reaction with lanthanide(III) ions yields [Ln^III(H₃L)₂]X₃?solvents (L = L¹, L²; X = Cl^?, NO₃^?; solvents = MeOH or H₂O). All complexes were characterised by microanalysis, infrared spectroscopy, high resolution mass spectrometry and solid-state photoluminescence measurements. The crystal structures of [Tb^III(H₃L¹)₂]Cl₃·6MeOH, [Dy(H₃L¹)₂]Cl₃·6MeOH, [Eu^III(H₃L¹)₂]Cl₃·6MeOH and [Tb^III(H₃L¹)₂](NO₃)₃ reveal high-crystallographic ?3 symmetry at the O₆-coordinated octahedral lanthanide(III) ions and that the tripodal ligands are bound in zwitterionic form: the protons from the phenolic oxygens have migrated to the amino nitrogens. Photoluminescence measurements indicate various degrees of energy transfer of the ligand chromophore to the lanthanide ions, as both ligand and lanthanide emission features are observed. Despite the high-crystallographic symmetry and the likely small transverse magnetic anisotropy of the complexes, no evidence of slow relaxation of the magnetisation, characteristic of a single-molecule magnet, was observed for [Tb^III(H₃L¹)₂]Cl₃·MeOH·3H₂O, [Dy^III(H₃L¹)₂]Cl₃·6H₂O, [Ho^III(H₃L¹)₂](NO₃)₃·2H₂O, [Er^III(H₃L¹)₂]·H₂O and [Tb^III(H₃L¹)₂](NO₃)₃ down to 2.0 K.     

Synthesis and crystal structure of yttrium(III) and lanthanide(III) complexes with a new terpyridine-like ligand 2,4-bis(3,5-dimethylpyrazol-1-yl)- 6-diethylamino-1,3,5-triazine

A new planar aromatic tridentate terpyridine-like ligand, 2,4-bis(3,5-dimethylpyrazol-1-yl)-6-diethylamino-1,3,5-triazine (L), has been synthesized and the structures of its complexes [YL(NO₃)₃] (1) and [LnL(NO₃)₃(H₂O)]L [Ln?=?La (2), Ce (3), Pr (4), Nd (5), Eu (6)] have been determined by X-ray crystal structural analysis. The structures of the five lanthanoid complexes are isomorphous and isostructural but different from the crystal structure of the yttrium complex [YL(NO₃)₃]. The latter shows a nine-coordinate metal center whereas the crystal structure of the lanthanoid complexes [LnL(NO₃)₃(H₂O)]L show a 10-coordinate metal center. The?π–π?stacking and hydrogen bonding between the coordinated and uncoordinated L molecules sensitized the Ln luminescence. The thermal behavior of the ligand and its complexes is discussed.     

Spectral characterization and antimicrobial activity of Cu(II) and Fe(III) complexes of 2-(5-Cl/NO2-1H-benzimidazol-2-yl)-4-Br/NO2-phenols

The compounds of 2-(5-chloro/nitro-1H-benzimidazol-2-yl)-4-bromo/nitrophenols (HL_X : X = 1–4) and their copper(II) nitrate and iron(III) nitrate complexes have been synthesized and characterized. The structures of the complexes were confirmed on the basis of elemental analysis, thermal gravimetric analysis, molar conductivity and magnetic moment measurements, FT-IR, mass, and UV-Vis spectroscopy techniques. The complexes show high-thermal stability with >350°C m.p. In all complexes, the ligands are bidentate via one imine nitrogen and a phenolate oxygen. Cu(II) complexes having 1 : 2 M : L ratio are classified as non-electrolytes, whereas 1 : 1 M : L ratio is observed in Fe(III) complexes except [Fe(L₃)₂(H₂O)₂](NO₃) ? 3H₂O. The antimicrobial activities of the ligands and the complexes were evaluated using the disc diffusion method in DMSO as well as minimum inhibitory concentration dilution method against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Proteus mirabilis. Antifungal activities were reported for Candida albicans. The complexes [Fe(L₃)₂(H₂O)₂](NO₃) ? 3H₂O and [Cu(L₃)₂] ? 2H₂O are more effective against S. epidermidis than ciprofloxacin.     

Ni(II) and Cu(II) complexes of new unsymmetrical N2O2 Schiff bases derived from 3-(2-aminobenzylimino)-1-phenylbutan-1-ol: synthesis,structure, antibacterial properties,and electrochemistry

Two new N₂O₂ unsymmetrical Schiff bases, H₂L¹ = 3-[({o-[(E)-(o-hydroxyphenyl)methylideneamino]phenyl}methyl)imino]-1-phenyl-1-buten-1-ol and H₂L² = 3-[({o-[(E)-(2-hydroxy-1-naphthyl)methylideneamino]phenyl}methyl)imino]-1-phenyl-1-buten-1-ol, and their copper(II) and nickel(II) complexes, [CuL¹] (1), [CuL²] (2), [NiL¹] (3), and [NiL²] (4), have been synthesized and characterized by elemental analyses and spectroscopic methods. The crystal structures of these complexes have been determined by X-ray diffraction. The coordination geometry around Cu(II) and Ni(II) centers is described as distorted square planar in all complexes with the CuN₂O₂ coordination more distorted than the Ni ones. The electrochemical studies of these complexes indicate a good correlation between the structural distortion and the redox potentials of the metal centers. The ligand and metal complexes were also screened for their in vitro antibacterial activity.     

Pb(II) and Bi(III) complexes involving a Schiff base ligand: syntheses,structures, physical,and antioxidant properties

Two new complexes, {[PbL(NO₃)₂H₂O]H₂O}_n (1) and [BiL₂(NO₃)₂]NO₃ (2), based on (E)-3-chloro-6-[2-(pyrazin-2-ylmethylene)hydrazinyl]pyridazine (L) were synthesized and characterized by IR spectra, single-crystal X-ray diffraction, and elemental analyzes. X-ray single crystal diffraction experiments of 1 and 2 display that extensive hydrogen bonds and π…π stacking interactions construct the 1-D infinite chain {[PbL(NO₃)₂H₂O]H₂O}_n and [BiL₂(NO₃)₂]NO₃ into two 3-D supramolecular frameworks. Interestingly, pure phase PbO nano-particles were synthesized by thermolysis of 1 and characterized by scanning electron microscopy and X-ray powder diffraction analyzes. Furthermore, antioxidant activities of L, 1, and 2 were also studied.     

Synthesis,structure, and urease inhibitory activities of Co(III), Mn(II) and Zn(II) complexes with hydrazone derived from protocatechuic acid

[Co^III(L₁)₂·H₂O]NO₃ (1), [Mn^II(L₁)₂·H₂O] (2), and [Zn^II(L₁)₂·H₂O] (3) with a hydrazone derived from protocatechuic acid (HL₁ = C₁₅H₁₃N₃O₃) were designed, synthesized, and characterized by C, H, N elemental analyses, single-crystal X-ray diffraction, and IR spectra, which revealed that the three complexes are similar structures. Docking study has been done. The urease inhibitory activities of the three complexes were tested. Complexes 1 and 3 showed strong inhibitory activity against jack bean urease with IC₅₀ values of 45.9 and 11.64 μM. Complex 2 had no obvious inhibitory activity to urease; the IC₅₀ was > 50 μM.     

Synthesis,crystal structure,antioxidation and fluorescence of two lanthanide complexes with a noncyclic polyether Schiff base ligand

Two lanthanide (Sm and La) complexes with the Schiff base ligand bis(3-methoxysalicylidene)-3-oxapentane-1,5-diamine (Bod) have been synthesized and characterized by physico-chemical and spectroscopic methods. [Sm(Bod)(NO₃)₃] {bis(3-methoxysalicylidene)-3-oxapentane-1,5-diamine samarium(III) trinitrate} (1) is a discrete mononuclear species and [La(Bod)(NO₃)₃(DMF)]_n {bis(3-methoxysalicylidene)-3-oxapentane-1,5-diamine dimethylformamide lanthanum(III) trinitrate}_n (2) formed an inorganic coordination polymer. In the two complexes, the metal ions are both ten-coordinate and the geometric structure around the Ln(III) ions can be described as distorted hexadecahedral. An antioxidant assay in vitro shows that complexes 1 and 2 exhibit better scavenging activity than both the ligand and the usual antioxidants on hydroxyl and superoxide radicals. Under excitation at room temperature, a red shift in the fluorescence band of the ligand in the complexes compared with that of the free ligand can be attributed to coordination of the rare earth ions to the ligand. Furthermore, 1 produced characteristic Sm(III) luminescence, which indicates the ligand Bod is a good organic chelator to absorb energy and transfer it to the Sm³⁺ ion.     

Lanthanide(III) Nitrate Complexes of Two 17 Membered N3O2-Donor Macrocycles

The interaction of lanthanide(III) ions with two N₃O₃-macrocycles, L¹ and L², derived from 2,6-bis(2-formylphenoxymethyl)pyridine and 1,2-diaminoethane has been investigated. Schiff-base macrocyclic lanthanide(III) complexes LnL¹(NO₃)₃ · xH₂O (Ln = Nd, Sm, Eu or Lu) have been prepared by direct reaction of L¹ and the appropriate hydrated lanthanide nitrate. The direct reaction between the diamine macrocycle L² and the hydrated lanthanide(III) nitrates yields complexes LnL²(NO₃)₃· H₂O only for Ln = Dy or Lu. The reduction of the Schiff-base macrocycle decreases the complexation capacity of the ligand towards the Ln(III) ions. The complexes have been characterised by elemental analysis, molar conductivity data, FAB mass spectrometry, IR and, in the case of the lutetium complexes, ¹H NMR spectroscopy.     

Carboxylate-bridged copper(II) complexes: synthesis,crystal structures,and superoxide dismutase activity

Two copper(II) complexes, [Cu₂(μ-benzoato)(L¹)₂]NO₃·2H₂O (1) and [Cu₂(μ-succinato)(L²)₂(H₂O)]ClO₄ (2), have been synthesized, where L¹ = N′-[(E)-phenyl(pyridin-2-yl)methylidene]benzoylhydrazone and L² = N′-[(E)-pyridin-2-ylmethylidene]benzoylhydrazone. These complexes were characterized including by single-crystal X-ray diffraction studies. The copper is five-coordinate in 1 while in 2 one copper is five-coordinate and the other is six-coordinate. Electrochemical behavior of these complexes was measured by cyclic voltammetry. The conproportionation equilibrium constants (K_con) for both complexes have been estimated. The superoxide dismutase (SOD) activities of 1 and 2 were measured by nitro blue tetrazolium assay. Complex 1 has better SOD activity than 2.     

Self-assembled biomimetic catalysts: studies of the catalase and peroxidase activities of Mn(III)-Schiff base complexes

Five Mn(III) nitrate complexes have been synthesized from dianionic hexadentate Schiff bases obtained by the condensation of 3-ethoxy-2-hydroxybenzaldehyde with different diamines. The complexes have been characterized by elemental analysis, ESI mass spectrometry, IR and ¹H NMR spectroscopy, r. t. magnetic, and molar conductivity measurements. Parallel-mode EPR spectroscopy of 1 is also reported. Ligand H₂L³ and complexes [MnL¹(H₂O)₂](NO₃)(CH₃OH) (1), [MnL³(H₂O)₂]₂(NO₃)₂(CH₃OH)(H₂O) (3), and [MnL⁴(H₂O)₂](NO₃)(H₂O)₂ (4) were crystallographically characterized. The X-ray structures show the self-assembly of the Mn(III)–Schiff base complexes through µ-aquo bridges between neighboring axial water molecules and also by π–π stacking interactions, establishing dimeric and polymeric structures. The peroxidase and catalase activities of the complexes have been studied. Complexes with the shorter spacer between the imine groups (1–2) behave as better peroxidase and catalase mimics, probably due to their ability to coordinate the hydrogen peroxide substrate to manganese.     

Mixed ligand Cu(II) complexes containing o-vanillin-l-tryptophan Schiff base and heterocyclic nitrogen bases: synthesis,structural characterization,and biological properties

[Cu(L)] (1) and mixed ligand copper(II) complexes [Cu(L)(A)] (2 and 3), where L is the Schiff base derived from o-vanillin and l-tryptophan and A is pyridine (2) and imidazole (3), were synthesized and characterized using conventional and spectral techniques. 2 was structurally characterized using single crystal X-ray crystallography showing that Cu(II) is coordinated through N₂O₂ donors in a square plane. The EPR spectra of the complexes in frozen solution support a square-based structure. Electrochemical behavior of the complexes has been studied by cyclic voltammetry. The DNA-binding properties of L and 1–3 with calf thymus DNA were investigated by spectral and kinetic methods. For all the complexes, the maximum value of binding constant (0.38 × 10⁶) was achieved with 3 by spectroscopic titration. The ability of compounds to break pUC19 DNA was checked by gel electrophoresis. The ligand and copper complexes exert cytotoxicity against MCF-7 cell line.     

Synthesis,Characterization and Antifungal Activity of Metal Complexes of 2-(5-((2-Chlorophenyl)Diazenyl)-2-Hydroxybenzylidene) Hydrazinecarbothioamide

Abstract

New metal complexes of Co(II), Cu(II), Ni(II), Zn(II), Mn(II), Fe(III), Ru(III), UO₂(II), and VO(II) with the Schiff base, 2-(5-((2-chlorophenyl)diazenyl)-2-hydroxy- benzylidene) hydrazine-carbothioamide (H₂L) have been prepared and characterized by elemental and thermal analyses, FT-IR, UV–Vis, mass spectra, ¹H-NMR, and ESR as well as conductivity and magnetic moments measurements. The IR spectra showed that the ligand acts as neutral tridentate, neutral bidentate or monobasic tridentate ligand. The geometries of metal complexes were either octahedral or square pyramidal. The ESR spectra of the solid copper(II) complexes indicated an axial symmetry type of a d_(x2-y2) ground state with considerably ionic or covalent environment. The effect of the presence of an azo group on the biological activity of the ligand was investigated. The ligand and its complexes are biologically inactive due to the presence of azo group.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the related elements to view the free supplemental file.     

Synthesis,spectroscopic (IR,electronic, FAB-mass,and PXRD), magnetic,and antimicrobial studies of new iron(III) complexes containing Schiff bases and substituted benzoxazole ligands

Mixed ligand complexes of iron(III), [Fe(sb)₂(py)Cl]?·?2H₂O (1–9) [where sbH?=?Schiff bases (derived from condensation of 2-aminopyridine (sapH), 2-aminophenol (saphH), o-toluidine (o-smabH), aminobenzene (sabH), p-toluidine (p-smabH), 3-nitroaniline (snabH), and anthranilic acid (saaH) with salicylaldehyde and substituted (mercapto-)benzimidazole (mbzH), {2-(o-hydroxyphenyl)}benzoxazole, (pboxH)], have been synthesized by the interactions of iron(III) chloride with corresponding ligands in 1?:?2 molar ratio in refluxing pyridine. These complexes have been characterized by elemental analyses, melting points, spectral, and magnetic studies. Powder X-ray diffraction studies of some representative complexes are also reported herein. The antibacterial and antifungal activities of the free ligands and their iron(III) complexes were found in vitro. The complexes showed good antibacterial and antifungal effect to some bacteria and fungi. Two standard antibiotics (chloromphenicol and terbinafine) were used for comparison with these complexes.     

Variation in coordinative property of two different N<Subscript>2</Subscript>O<Subscript>2</Subscript> donor Schiff base ligands with nickel(II) and cobalt(III) ions: characterisation and single crystal structure elucidation

A nickel(II) and a cobalt(III) complex of two different potentially tetradentate Schiff bases with different binding modes have been synthesised. The nickel(II) complex [NiL¹] · CH₃OH (1) was formed, on reacting the metal salt with a perfectly symmetrical N₂O₂ tetradentate Schiff base ligand H ₂ L ¹ , which is the 1:2 condensation product of 1,3-diamino propane and 2-hydroxyacetophenone. The cobalt(III) complex [Co(HL²)₃] · (ClO₄)₃ · H₂O (2) was synthesised using an asymmetric N₂O₂ tetradentate Schiff base ligand HL ² on condensing N,N-dimethyl-1,3-diamino propane with o-vanillin in 1:1 mmol ratio. Although both Schiff bases are N₂O₂ functionalised, they showed variation in their coordinative property with nickel(II) and cobalt(III) ions. Both the complexes were characterised by IR spectroscopy and cyclic voltammetry and their single crystal structures clearly indicate that 1 is a mononuclear species whereas 2 is a hydrogen-bonded dimer.     

Synthesis and electrocatalytic reactivity for water oxidation of two cerium complexes

Two cerium complexes with and without manganese ion, [MnCe₄(dipic)₆(H₂O)₂₀][Ce(dipic)₃]₂·7H₂O (dipic = dipicolinate) (1) and [Ce₂(H₂O)₄(O₂CMe)₆][Ce(H₂O)₄(NO₃)₂(O₂CMe)]₂·2H₂O·2MeOH (2), have been prepared, and their electrocatalytic reactivity for water oxidation has been investigated. Compound 1 is a heterometallic 3d-4f compound which possesses four Ce(IV) ions, two Ce(III) ions, and one Mn(II). Compound 2 is composed of three neutral parts, one of which is a dinuclear cerium molecule lying on an inversion center, and the other two are symmetric monomer units; the four cerium ions in 2 are all Ce(III). Electrochemical studies of 1 and 2 show that 1 can catalyze water oxidation at the potential ~1.5 V with an overpotential of ca. 900 mV versus NHE. Control potential electrolysis (CPE) experiments at 1.50 V of 1 displayed a stable current density of 2.5 mA/cm², and the calculated Faradaic efficiency is 60%. However, no electrocatalytic reactivity was observed for 2. By comparison experiments, it was found that the electrocatalysis of 1 may result from the cooperative catalytic effect of the 4f cerium ion and 3d transition metal manganese ion.     

一个手性四核铜配合物的合成、结构和CD光谱

香草醛和L-2-氨基-3-苯基-1-丙醇缩合得到的手性希夫碱配体(L-H2vap)与Cu(ClO4)2.6H2O,Gd(NO3)3.6H2O和三乙胺在4-羟基苯甲酸的存在下反应得到L-[Cu4(Hvap)2(vap)2(MeOH)2](ClO4)2.2MeOH.H2O(1)。通过元素分析、红外、热重分析和固体CD光谱对1结构进行了表征,并通过X-射线单晶衍射确定其单晶结构,结果表明1属于单斜晶系,P21手性空间群,Z=2,包含船型{Cu4O4}结构。1的Cu4簇通过配体、溶剂分子和高氯酸根离子的氧原子间的氢键沿b轴形成超分子链。固体CD光谱证实了1的手性。     

Cerium(IV) Nitrate Complexes With Bidentate Phosphine Oxides

The reactions between ceric ammonium nitrate, (NH₄)₂Ce(NO₃)₆, (CAN) and the bidentate phosphine oxides, 4,5-bis(diphenylphosphine oxide)-9,9-dimethylxanthene (L¹), oxydi-2,1-phenylene bis(diphenylphosphine dioxide) (L²), 1,2-bis(diphenylphosphino)ethane dioxide (L³) and 1,4-bis(diphenylphosphino)butane dioxide, L⁴ have been investigated. The crystal structures of the molecular Ce(NO₃)₄L¹ ( 1 ), and ionic [Ce(NO₃)₃L³₂][NO₃]⋅CHCl₃ ( 3 ), [Ce(NO₃)₃L³₂][NO₃] ( 4 ) and the polymeric [Ce(NO₃)₃L⁴_1.5] [NO₃] ( 5 ) and the cerium(III) complex [Ce(NO₃)₂L¹₂][NO₃] ( 2 ) are reported. The thermal stability of the complexes has been examined by thermogravimetry with the gaseous decomposition products analysed by infrared spectroscopy. Evolution of CO₂ is found for both Ce(III) and Ce(IV) complexes with the later also forming NO₂. The formation of the complexes in solution has been studied by ³¹P NMR spectroscopy and further complexes [Ce(NO₃)₃L¹₂]⁺[NO₃]⁻ and [Ce(NO₃)₂L¹₃]²⁺2[NO₃]⁻ identified in CD₃CN solution. The complex ( 1 ) exists as a single molecular species in solution and is stable in dichloromethane whilst ( 3 ) decomposes on standing in both CD₂Cl₂ and CD₃CN to Ce(III) containing species. Complexes of L² have been identified by solution ³¹P NMR spectroscopy and these decompose in solution to give Ce(NO₃)₃L²₂. This study represents the first structural characterisations of Ce(IV) complexes with bidentate phosphine oxides.     

Synthesis and thermal decomposition kinetics of La(III) complexwith unsymmetrical Schiff base ligand

A new unsymmetrical solid Schiff base (LLi) was synthesized using L-lysine, o-vanillin and 2-hydroxy-l-naphthaldehyde. Solid lanthanum(III) complex of this ligand [LaL(NO₃)]NO₃·2H₂O have been prepared and characterized by elemental analyses, IR, UV and molar conductance. The thermal decomposition kinetics of the complex for the second stage was studied under non-isothermal condition by TG and DTG methods. The kinetic equation may be expressed as: dα/dt=Ae^−E/RT(1−α)². The kinetic parameters (E, A), activation entropy ΔS ^# and activation free-energy ΔG ^# were also gained.     

Synthesis,structural characterization,molecular docking,and urease inhibition studies of dinuclear cobalt(II) complexes derived from 3,5-bis(pyridin-2-yl)-4-amino-1,2,4-triazole

Two dinuclear Co(II) complexes, [Co₂(L)₂(EtOH)₄]·4ClO₄ (1) and [Co₂(L)₂(H₂O)₂(NO₃)₂]·2NO₃ (2) (L?=?4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole), have been obtained and characterized by IR, elemental analysis, and single-crystal X-ray diffraction analysis. The stabilization of their crystal lattices is maintained by strong H-bonds between counterions and host framework, which lead to various supramolecular architectures. The urease inhibitory properties of 1, 2, and L were investigated, where the two complexes revealed strong urease inhibition activities. Docking simulations of 2 have been performed with H. pylori urease (PDB code: 1E9Z) to rationalize their binding models.