Synthesis,characterization, and structure of a new cobalt(II) Schiff-base complex with quinoxaline- 2-carboxalidine-2-amino-5-methylphenol

The mononuclear cobalt(II) complex [CoL₂] · H₂O (where HL is quinoxaline-2-carboxalidine-2-amino-5-methylphenol) has been prepared and characterized by elemental analysis, conductivity measurement, IR, UV-Vis spectroscopy, TG?DTA, and X-ray structure determination. The crystallographic study shows that cobalt(II) is distorted octahedral with each tridentate NNO Schiff base in a cis arrangement. The crystal exhibits a 2-D polymeric structure parallel to [010] plane, formed by O?H ··· N and O?H ··· O intermolecular hydrogen bonds and π?π stacking interactions, as a racemic mixture of optical enantiomers. The ligand is a Schiff base derived from quinoxaline-2-carboxaldehyde.     

Synthesis,structure, cytotoxic activities,and DNA-binding of 1-D copper(II) and zinc(II) coordination polymers

Two 1-D coordination polymers have been synthesized and identified as [Zn(ox)(en)] _n (H₂O)_{2 n} (1) and [Cu₂(dmeo)(N₃)₂] _n (2), where en represents diaminoethane, ox and dmeo stand for dianions of oxalic acid and N,N′-bis[2-(dimethylamino)ethyl]oxamide, respectively. Polymer 1 was characterized by elemental analysis, molar conductance measurement, IR and electronic spectra, and single-crystal X-ray diffraction. Polymer 1 consists of 1-D chains bridged by oxalate. The Zn^II can be described as a distorted octahedral environment and the Zn^II···Zn^II separation through the μ-oxalato-bridge is 5.5420(9)?Å. Hydrogen bonds assemble the coordination polymers to a 3-D supermolecular structure. The crystal structure of 2 has been reported previously. However, the bioactivities were not studied. The DNA-binding properties and cytotoxic activities of the two coordination polymers are investigated. The results suggest that the two polymers interact with HS-DNA in groove binding with binding affinity following the order of 1?>?2, which is consistent with their anticancer activities.     

Synthesis,crystal structure and magnetic property of a three-dimensional manganese(II) complex

The solvothermal reaction of MnCl₂·4H₂O, H₂asp and CH₃ONa gave rise to a new manganese(II) complex, {[Mn(asp)(H₂O)]·(H₂O)₂} _n (1) (H₂asp?=?5-aminoisophthalic acid). Single-crystal X-ray diffraction analysis reveals that complex 1 is a three-dimensional consisting of two-dimensional layers extended by hydrogen bonding interactions. The two-dimensional layer contains 8-, 14-, and 16-membered rings. A variable temperature magnetic measurement of 1 displays weak antiferromagnetic behavior.     

Structure,spectroscopic, and magnetic properties of a new cobalt(II) complex with 5-sulfoisophthalic anion

A complex of [Co(H₂SIP)(Phen)(H₂O)₃] ? H₂O (H₂SIP = 5-sulfoisophthalic anion, Phen = 1,10-phenanthroline) has been synthesized by hydrothermal reaction. Crystal structure determination revealed that the complex crystallizes in the monoclinic space group P2(1)/c, in which Co(II) is distorted octahedral coordinating with one carboxylate sulfonate ligand, one phen, and three coordinated waters. Molecules of [Co(H₂SIP)(Phen)(H₂O)₃] ? H₂O are connected to form a 3-D structure by intermolecular hydrogen bonds and π–π stacking interactions. IR spectra, UV-Vis spectra, and magnetic susceptibilities have been analyzed to obtain values of the ligand field and magnetic parameters: Α = 1.33, λ = ?102.3 cm^?1, κ = 0.96, and Δ = 252.2 cm^?1.     

Synthesis and structure of a 1-D copper(II) coordination polymer bridged both by oxamido and carboxylate: in vitro anticancer activity and reactivity toward DNA and protein BSA

A 1-D copper(II) coordination polymer formulated as {[Cu₂(bdpox)(dabt)](NO₃)·H₂O}_n, where H₃bdpox and dabt denote N-benzoate-N′-[3-(diethylamino)propyl]oxamide and 2,2′-diamino-4,4′-bithiazole, respectively, was synthesized and characterized by elemental analyses, molar conductance measurement, IR and electronic spectra studies, and single-crystal X-ray diffraction. The crystal structure analysis reveals that copper(II) ions are bridged by both cis-oxamido and carboxylato groups to form a 1-D coordination polymer with corresponding Cu···Cu separations of 5.2420(10) and 5.1551(8) Å. The endo- and exo-copper(II) ions of the cis-oxamido-bridge are located in distorted square-planar and square-pyramidal geometries, respectively. There is a 2-D hydrogen bonding network in the crystal. The in vitro anticancer activities suggest that the copper(II) complex is active against selected tumor cell lines. The reactivities toward herring sperm DNA and bovine serum albumin (BSA) reveal that the copper(II) complex can interact with DNA by intercalation and effectively quench the intrinsic fluorescence of BSA via a static mechanism. The influence of hydrophobicity of the substituents in bridging ligands on DNA and protein binding properties and the in vitro anticancer activities of such copper(II) polymers is discussed.     

Synthesis,crystal structure,and properties of a seven-coordinate manganese(II) complex formed with the tripodal tetradentate ligand tris (N -methylbenzimidazol-2-ylmethyl)amine and salicylate

A seven-coordinate manganese(II) complex with the tripod tetradentate ligand tris(N-methylbenzimidazol-2-ylmethyl)amine (Mentb), [Mn(Mentb)(salicylate)(DMF)](ClO₄) ? (DMF), was synthesized and characterized by elemental, electrical conductivity, infrared, and UV-Vis spectral measurements. The crystal structure of the complex has been determined by single-crystal X-ray diffraction. Mn^II is bonded to a Mentb, a salicylate and dimethylformamide through four nitrogens and three oxygens, resulting in seven-coordination. Cyclic voltammograms of the complex indicate a quasi-reversible Mn³⁺/Mn²⁺ couple. The X-band electron paramagnetic resonance spectrum exhibits a six-line manganese hyperfine pattern with g = 2, A = 93, confirming that the material is high-spin Mn(II).     

Synthesis,crystal structure and magnetic properties of a new 1-D oxamidate-bridged Cu(II)-Mn(II) polymer

A new coordination polymer, {[Cu(aeop)Mn(H₂O)₃]₂}_n (H₄aeop = N′-(2-aminoterephthalic acid)-N′′-(1,3-propanediamine)oxamidate), has been synthesized and characterized structurally and magnetically. This complex features a 1-D ladder-like chain structure constructed from neutral tetranuclear units through the syn-anti carboxylate bridges. This crystal forms in the triclinic system, space group P 1, with a = 9.653(1) Å, b = 9.686(1) Å, c = 10.903(1) Å, α = 80.984(1)°, β = 69.776(1)°, γ = 80.729(1)° and z = 2. The relationship between its magnetic properties and structure has also been investigated.     

Synthesis, structure, and magnetic properties of two 1-D helical coordination polymeric Cu(II) complexes

Two helical coordination polymeric copper(II) complexes bearing amino acid Schiff bases HL or HL′, which are condensed from 2-hydroxy-1-naphthaldehyde with 2-aminobenzoic acid or l-valine, respectively, have been prepared and characterised by X-ray crystallography. In [CuL]_n (1) the copper(II) atoms are bridged by syn-anti carboxylate groups giving infinite 1-D right-handed helical chains which are further connected by weak C-H?Cu interactions to build a 2-D network. While in [CuL′]_n (2) the carboxylate group acts as a rare monatomic bridge to connect the adjacent copper(II) atoms leading to the formation of a left-handed helical chain. Magnetic susceptibility measurements indicate that 1 exhibits weak ferromagnetic interactions whereas an antiferromagnetic coupling is established for 2. The magnetic behavior can be satisfactorily explained on the basis of the structural data.     

Synthesis and study of the structure of new 3d-metal coordination compounds with substituted 2-amino-4(5H)-ketothiophens

A series of new 3d-metal complexes based on 2-amino-3-(1-methylbenzimidazol-2-yl)-4(5H)-ketothiophen (HL¹) and 2-amino-3-(2-benzothiazolyl)-4(5H)-ketothiophen (HL²) were synthesized. Compounds of the general formulas [ML₂] and [M(HL¹)₂Cl₂] (where M = Co²⁺, Ni²⁺, Zn²⁺, Cu²⁺) were prepared by the reaction of the above mentioned ligands with the corresponding acetate (for [ML₂]) or chloride (for [M(HL¹)₂Cl₂]) salts in a methanol or a methanol–chloroform medium. The choice of the anion in the initial metal salt, as well as the selection of the ligand, is crucial for obtaining coordination compounds with a neutral or deprotonated form of the 2-amino-4(5H)-ketothiophens. Thus, in contrast to HL¹, complexes with the neutral form of HL² cannot be obtained under the same conditions. All the complexes were studied by spectroscopic methods and X-ray crystallography (for [CuL¹₂] · H₂O). The coordination polyhedron of the copper atom is formed by four nitrogen atoms from two ligand anions and the geometry of the coordination sphere is intermediate between tetrahedral and square-planar.     

Syntheses,structural characterizations and microbial activities of Ni(II) and Zn(II) 5-aminoisophthalate coordination polymers

Two coordination polymers with 5-aminoisophthalic acid (H₂aip), [Ni(μ-aip)(H₂O)₂(tmeda)]_n (1) and {H₂dap[Zn₂(μ-aip)(μ₃-aip)₂]?9H₂O}_n (2) (H₂aip = 5-aminoisophthalic acid, tmeda = N,N,N′-N′-tetramethylethylenediamine, dap = 1,3-diaminopropane) have been synthesized. Elemental and thermal analyses, magnetic susceptibilities, IR, AAS, mass and UV–vis spectroscopic studies have been performed to characterize the compounds. Nickel(II) has octahedral geometry by two oxygens of different carboxylates, bidentate, tmeda as bidentate chelating and two water ligands. Zn(II) has tetrahedral geometry by three oxygens of different carboxylate groups and one nitrogen by amine of aip. 1 crystallizes in the orthorhombic crystal system with space group Pccn and 2 in monoclinic crystal system with space group P2₁/c. Complex 2 exhibits photoluminescence properties in the solid state at room temperature. This study determined the susceptibility patterns of 1 and 2 against bacterial, yeast and mold micro-organisms. Antimicrobial activities were done on 12 different micro-organisms using the micro-dilution method. Tested microbial species were inhibited by 1 with a Minimum inhibitory concentrations (MIC) of 375–3000 μg mL^?1. Compound 2 showed antimicrobial activities against tested micro-organisms with a MIC of 188–1500 μg mL^?1. Compound 2 showed antibacterial activity against Legionella pneumophila sg1 375 μg mL^?1 (MIC value).     

A twofold interpenetrated 3-D Cu(II) coordination polymer based on 5-(pyridin-4-yl)isophthalic acid: synthesis,crystal structure,and magnetic properties

A new copper(II) coordination polymer, [Cu(PIA)·2H₂O]_n (1) [H₂PIA = 5-(pyridin-4-yl)isophthalic acid], has been synthesized and characterized by elemental analysis, IR spectroscopy, TGA, powder, and single-crystal X-ray diffraction. Structural analysis shows that each PIA^2? in 1 bridges three Cu(II) ions, and likewise each Cu(II) ion connects to three PIA^2? ligands, giving a 3-D framework with utp topology and left-/right-handed helical channels. Interestingly, two such identical frameworks interlock with each other to generate a twofold interpenetrated structure that is stabilized by hydrogen bonding and π–π interactions. In addition, the thermal stability and the magnetic properties of 1 have been investigated.     

Synthesis, crystal structure, spectroscopic and photoluminescence studies of manganese(II), cobalt(II), cadmium(II), zinc(II) and copper(II) complexes with a pyrazole derived Schiff base ligand

Varying coordination modes of the Schiff base ligand H₂L [5-methyl-1-H-pyrazole-3-carboxylic acid (1-pyridin-2-yl-ethylidene)-hydrazide] towards different metal centers are reported with the syntheses and characterization of four mononuclear Mn(II), Co(II), Cd(II) and Zn(II) complexes, [Mn(H₂L)(H₂O)₂](ClO₄)₂(MeOH) (1), [Co(H₂L)(NCS)₂] (2), [Cd(H₂L)(H₂O)₂](ClO₄)₂ (3) and [Zn(H₂L)(H₂O)₂](ClO₄)₂ (4), and a binuclear Cu(II) complex, [Cu₂(L)₂](ClO₄)₂ (5). In the complexes 1-4 the neutral ligand serves as a 3N,2O donor where the pyridine ring N, two azomethine N and two carbohydrazine oxygen atoms are coordinatively active, leaving the pyrazole-N atoms inactive. In the case of complex 5, each ligand molecule behaves as a 4N,O donor utilizing the pyridine N, one azomethine N, the nitrogen atom proximal to the azomethine of the remaining pendant arm and one pyrazole-N atom to one metal center and the carbohydrazide oxygen atom to the second metal center. The complexes 1-4 are pentagonal bipyramidal in geometry. In each case, the ligand molecule spans the equatorial plane while the apical positions are occupied by water molecules in 1, 3 and 4 and two N bonded thiocyanate ions in 2. In complex 5, the two Cu(II) centers have almost square pyramidal geometry (τ = 0.05 for Cu1 and 0.013 for Cu2). Four N atoms from a ligand molecule form the basal plane and the carbohydrazide oxygen atom of a second ligand molecule sits in the apex of the square pyramid. All the complexes have been X-ray crystallographically characterized. The Zn(II) and Cd(II) complexes show considerable fluorescence emission while the remaining complexes and the ligand molecule are fluorescent silent.     

Synthesis,crystal structure and magnetic properties of a three-dimensional cyano-bridged heterometallic complex of manganese(II) and molybdenum(IV)

A bimetallic cyano-bridged complex {[Mn(ImH)(H₂O)₂]₂[Mo(CN)₈]·4H₂O} _n (ImH?=?imidazole) has been prepared and characterized. Single-crystal X-ray analysis reveals that the complex crystallizes in space group C2/c with a?=?15.665(2), b?=?14.616(2), c?=?12.307(2)?Å, α?=?90, β?=?108.31(1), γ?=?90°. The structure of the complex demonstrates a three-dimensional network through cyano-bridges. Each Mo(IV) atom has six –CN–Mn linkages and two terminal cyano ligands arranged in a square antiprismatic arrangement. The Mn(II) atom is in a distorted octahedral environment formed by three MoCN?→?Mn linkages along with one imidazole and two water molecules in cis configuration. Variable temperature magnetic susceptibility shows an antiferromagnetic coupling between Mn²⁺ ions through the NC–Mo^IV–CN diamagnetic bridges within the three-dimensional network. The IR spectra have also been investigated.     

Synthesis,crystal structure,and magnetism of [Mn(hfac)2NIT(Ph-m-OPh)]

A new complex [Mn(hfac)₂NIT(Ph-m-OPh)] has been synthesized and structurally characterized by X-ray diffraction. It crystallizes in the monoclinic space group P2(1)/c. The structure consists of a 1-D chain with Mn(II) bridged by NIT(Ph-m-OPh). The manganese(II) is in a distorted octahedral environment formed by one oxygen from NIT(Ph-m-OPh) and three atoms from hexafluoro acetylacetone (hfac) in the equatorial plane and two oxygens from hfac and the other NIT(Ph-m-OPh) in the axial position. The units of [Mn(hfac)₂NIT(Ph-m-OPh)] are connected as a 1-D chain by Mn(II) and oxygen of N–O in bridging NIT(Ph-m-OPh) along the b-axis. The 2-D layer in the ab plane is formed via hydrogen interactions to connect neighboring chains. The complex exhibits intramolecular antiferromagnetic interactions between Mn(II) and NIT(Ph-m-OPh).     

Synthesis,characterization, and antibacterial activity of a manganese(II) complex of triaryltriazole

A manganese(II) complex of 4-(4-methylphenyl)-3,5-bis(2-pyridyl)-4H-1,2,4-triazole (MBPT) was synthesized and characterized by X-ray crystallography. [Mn(MBPT)₂(H₂O)₂](ClO₄)₂?·?4H₂O is a divalent mononuclear manganese(II) complex with manganese coordinated to four nitrogens from two triazole ligands and two oxygens from two water molecules in a slightly distorted octahedral geometry. The complex and ligand were tested in vitro for their antibacterial activities. The title complex showed a wide range of bactericidal activities.     

UV-visible spectroscopic and electrochemical study of the complex formation between Fe(II) and 5-amino-1,10-phenantroline (5-Aphen) in aqueous solution

The system Fe(II)-5-Aphen-H₂O was studied. The spectroscopic and electrochemical results show that only one stable complex between Fe(II) and 5-Aphen forms, having a 1:3 stoichiometric ratio. The spectrophotometry study allowed determination of the formation constant of the complex (log β₃ = 23.42 ± 0.06). Also, the stability of the complex was evaluated as a function of pH; it was found that it decomposed at low pH values depending on the concentration and a pseudo-first order kinetics constant associated with k′ = 0.011 min⁻¹. The results are in agreement with the electrochemical behaviour observed in the system, which indicated that at pH 1.33 the destruction of the complex [Fe(5-Aphen)3]²⁺ took place as a function of time; however, when the experiments were carried out at pH 6.19 the complex was stable. The thermodynamic data obtained through the use of MEDUSA allowed construction of predominance zone diagrams of the system Fe(II)-5-Aphen-H₂O under the experimental conditions used. The thermodynamic results represented in the PZD describe the experimental behaviour reported in this work.     

A new mixed ligand coordination polymer of Mn(II): structural aspect and cryomagnetic study

A new 1-D polymeric chain complex [Mn(pydc)(1,10-phen)]_n· nH₂O (pydc = pyridine-2,3-dicarboxylate, 1,10-phen = 1,10-phenanthroline) has been synthesised and characterised by elemental analysis, FT-IR spectrum, thermal analysis and variable temperature magnetic susceptibility studies. Single crystal X-ray diffraction study reveals that the central Mn(II) ion is in a distorted octahedral coordination geometry, and is coordinated to pydc and 1,10-phen. The complex shows interesting hydrogen bond modes involving the dicarboxylates and lattice water molecules. The presence of weak antiferromagnetic coupling with J = −0.72 cm⁻¹ for the complex has been concluded from the cryomagnetic susceptibility studies.     

Synthesis,crystal structure,and DNA binding of a new oxalato-bridged binuclear zinc(II) complex

A new binuclear zinc(II) complex bridged by μ-oxalate, and end-capped with 2,2′-bipyridine (bpy), [Zn₂(ox)(bpy)₄](ClO₄)₂ · H₂O, has been synthesized and characterized by elemental analyses, molar conductance, IR, and electronic spectra and single-crystal X-ray diffraction. The single-crystal X-ray analysis reveals that the [Zn₂(ox)(bpy)₄]²⁺ cation has two zinc(II) centers bridged by a planar bis(bidentate) oxalate group with Zn···Zn distance of 5.482(3) Å; each zinc(II) is in a distorted octahedral environment. The crystal structure is stabilized by non-classical C–H···O hydrogen bonds and π–π stacking interactions to form a 3-D supramolecular structure. The interaction of the complex with calf-thymus DNA (CT-DNA) was explored by using electronic and fluorescence spectra and viscosity measurements. The results reveal that the complex intercalates with CT-DNA with intrinsic binding constant of 4.1 × 10⁴ M^?1.     

Four Zn(II)/Cd(II)-3-amino-1,2,4-triazolate frameworks constructed by in situ metal/ligand reactions: Structures and fluorescent properties

Four Cd(II) and Zn(II) complexes with the in situ-generated ligand of 3-amino-1,2,4-triazolate (AmTAZ⁻) were isolated from the solvothermal reactions of the corresponding Cd(II) or Zn(II) salts with 5-amino-1H-1,2,4-triazole-3-carboxylic acid (AmTAZAc). Their structures were determined by single-crystal X-ray diffraction analysis. [Zn(AmTAZ)(CH₃COO)] (1) presents a two-dimensional framework constructed from Zn(II) ions and μ₃-AmTAZ⁻ ligands. A remarkable feature of [Zn₄(AmTAZ)₄(SO₄)(OH)(C₂O₄)_0.5]·2H₂O (2) is the construction of the building units of octagonal cylinders which interact with each other by sharing one face or overlapping, resulting in the formation of a three-dimensional framework with three kinds of 1D channels. [Cd(AmTAZ)Br] (3) crystallizes in a chiral space group P2₁2₁2₁, giving a homochiral three-dimensional framework with two types of helical channels (left- and right-handed). Different from the others, the 3-amino-1,2,4-triazole molecules in [Cd(AmTAZH)SO₄] (4) behave as neutral μ₂-2,4-bridges to connect the two-dimensional CdSO₄ sheets into a three-dimensional framework. Of all, 2 and 3 display different fluorescent properties probably due to different metal ions, coordination environments and structural topologies.