Synthesis,spectra and X-ray crystal structure of a new type of macrocyclic hexanuclear iron(III) cluster

A macrocyclic iron(III) 18-azametallacrown-6 compound, [Fe₆(5-Brashz)₆(H₂O)₆]?·?20H₂O(5-Brashz?=?N-acetyl-(5-bromosalicylhydrazide)), where the pentadentate ligands bridge the metal ions, was synthesized and characterized. Due to the meridional coordination of the ligand to the metal ion, the ligand is not only bridging the ring metal ions using a hydrazide N–N group, but also enforcing the stereochemistry of the metal ions as a propeller shape with alternating Λ/Δ configuration. The disc-shaped hexanuclear cluster is about 14.5?Å in diameter, 16.8?Å in thickness and has a vacant cavity in the center of the cluster.     

Synthesis,crystal structure,spectroscopy, and nuclease activity of copper(II) complexes containing N,N-bis(2-pyridylmethyl)amine ligand

[Cu(bpea)Cl]ClO₄ (1) and a new copper(II) complex [Cu(bpma)(Ph-COO)(H₂O)]ClO₄ (2) [bpea?=?N,N-bis(2-pyridylmethyl)ethylamine; bpma?=?N,N-bis(2-pyridylmethyl)methylamine] have been synthesized. Complex 2 was crystallized in monoclinic space group P2₁/c with unit cell parameters a ?=?16.460(6)?Å, b ?=?11.222(4)?Å, c?=?12.522(5)?Å, and β?=?97.985(6)°. Interactions of the complexes with calf thymus DNA (CT-DNA) have been investigated by UV absorption, fluorescence, and cyclic voltammetry; thus, modes of CT-DNA binding for the complexes have been proposed. Furthermore, DNA cleavage activities by the complexes were performed in the absence of any external agents. The influence of complex concentration or reaction time on the DNA cleavage was studied.     

Synthesis,crystal structure and magnetic properties of a dinuclear manganese(III) tetradentate Schiff-base complex

A dinuclear manganese(III) tetradentate Schiff-base complex, [Mn₂(salophen)₂(4,4′-bipy)₃](BPh₄)₂ (1) (salophen = N,N′-o-phenylene-bis(salicylideneaminato)), has been synthesized and structurally characterized. Compound 1 crystallized in the triclinic, P 1 space group, a = 13.431(4), b = 13.791(4), c = 13.886(4) Å, α = 73.599(5)°, β = 80.410(6)°, γ = 71.241(5)°, V = 2328.3(12) ų. Complex 1 contains two Mn(salophen) moieties bridged by 4,4′-bipy to form a dinuclear unit, with two terminal 4,4′-bipy ligands. Variable temperature magnetic susceptibility (2–300 K) shows very weak ferromagnetic interactions between the Mn(III) ions.     

Synthesis,crystal structure and magnetic property of a binuclear iron(III) citrate complex

The compound (Hql)₂[Fe₂(cit)₂(H₂O)₂]·4H₂O (1) [ql = quinoline, cit^4– = C(O^–)(CO^– ₂)(CH₂CO^– ₂)₂], prepared by reacting ferric nitrate, sodium citrate and quinoline in a molar ratio of 1:1:1 in aqueous solution, was characterized by density measurements, elementary analysis, i.r., X-ray crystallography and magnetic measurements. The X-ray crystallography results reveal that the molecule (1) consists of a binuclear iron(III) citrate anionic complex [Fe₂(cit)₂(H₂O)₂]^2– and two protonated quinolines [Hql]⁺. The anionic complex has a centro-symmetric structure, in which two Fe³⁺ ions are bridged by two ₂-alkoxo groups of the two deprotonated citrate ligands. The other coordination sites of the two slightly distorted octahedra are completed by all the carboxylate groups of the two cit^4– ligands in a monodentate mode, and two coordinated water molecules. Magnetic measurements indicate that the two Fe³⁺ ions are antiferromagnetically coupled below 200 K. A least-squares fit of variable-temperature (1.5–291 K) molar susceptibility data to a dimer model gave the coupling constant J/k = –6.35(7) K and Landé factor g = 2.052(9), where the spin-only Heisenberg–Dirac–van Vleck Hamiltonian is expressed as H = –2J S ₁ S ₂.     

Synthesis,crystal structure and magnetic properties of a new binuclear copper(II)-copper(II) complex of a macrocyclic oxamide

The binuclear metal complex [Cu(μ-exoO₂)cyclamCu(bpy)](ClO₄)₂·H₂O (bpy?=?2,2′-bipyridine and (exoO₂)cyclam?=?1,4,8,11-tetraazacyclotradecanne-2,3-dione) has been synthesized and characterized by single-crystal X-ray analysis and spectroscopic and magnetic measurements. The structure consists of homobinuclear [Cu(μ-exoO₂)cyclamCu(bpy)]²⁺ cations, a weakly coordinated water molecule and perchlorate ions. In each binuclear unit, Cu1, coordinated by four nitrogen atoms of the macrocyclic organic ligand is connected to Cu2 via the exo-cis oxygen atoms of the macrocyclic ligand with Cu···Cu separations of 5.151?Å; Cu2 assumes square-pyramidal geometry. Magnetic properties measured at 2–300?K show antiferromagnetic exchange between adjacent copper(II) ions.     

Synthesis,crystal structure and magnetic property of a maleonitriledithiolate nickel(III) complex containing an ammonium crown ether cation

The synthesis, molecular structure and spectroscopic and magnetic properties of (NH₄)₂(15-crown-5)₃[Ni(mnt)₂]₂ (mnt?=?maleonitriledithiolate dianion) are reported. The most notable structural feature of (NH₄)₂(15-crown-5)₃[Ni(mnt)₂]₂ is that the ions form a stacked structure with well-separated columns along the c and a axes. Variable temperature magnetic susceptibility measurements indicate strong antiferromagnetic interactions in the complex.     

Mononuclear and binuclear iron(III) complexes incorporating N4O3 coordinating heptadentate ligand: Synthesis,structure and magnetic properties

The N₄O₃ coordinating heptadentate ligand afforded the mononuclear [Fe^III(HL)][BPh₄] (1) and binuclear [Fe₂^IIIL(OAc)₂][BPh₄] (2) complexes. In complex 1, the ligand binds in a trianionic N₂O₃ fashion whereas in the case of 2 the ligand binds in the trianionic N₄O₃ form in which the iron ions are held together by μ-phenoxo and bis μ-acetato bridges. In 1, the Fe(III) center has a trigonal bipyramidal geometry (τ = 0.84) whereas in 2 both the Fe(III) centers have a distorted octahedral geometry. Complex 2 shows an intramolecular weak antiferromagnetic interaction. Gas phase geometry optimizations have been performed using density functional theory without any symmetry constraints. The gas phase optimized structures agree well with the X-ray structure.     

Synthesis,crystal structure and magnetic property of a one-dimensional copper(II) complex with 2,5-dimethylpyrazine-1,4-dioxide as bridging ligand

A one-dimensional polynuclear copper(II) complex [Cu(μ_1,6-dmpzdo)(SCN)₂] _n (where dmpzdo?=?2,5-dimethylpyrazine-1,4-dioxide) has been synthesized and its crystal structure determined by X-ray crystallography. The coordination geometry of Cu(II) atom is a square plane and each Cu(II) ion is connected by two μ_1,6-dmpzdo bridging ligands, leading to the formation of a one-dimensional chain. ESR spectra indicate magnetic coupling between the bridged Cu(II) ions. The fitting of the variable-temperature magnetic susceptibility data (4–300?K) gave 2J?=??68.69?cm^?1.     

Synthesis,magnetic property and DNA cleavage behavior of a new dialkoxo‐bridged diiron(III) complex

A new dialkoxo‐bridged diiron(III) complex, [Fe₂(BMA)₂(CH₃O)₂Cl₂]·2Cl·4CH₃OH ( 1 ) [BMA = N,N‐bis(2‐benzimidazolylmethyl)amine], was synthesized and characterized by UV‐visible absorption and infrared spectra and magnetic susceptibilities. The complex crystallizes in the monoclinic system, space group P2(1)/n, a = 12.9659(19) Å, b = 10.0278(16) Å, c = 17.919(2) Å, β = 93.766(8)° , V = 2324.8(6) ų, Z = 2, F(000) = 1036, D_c = 1.426 g cm^?3, µ = 0.908 mm^?1. According to X‐ray crystallographic studies, each Fe(III) ion lies in a highly distorted octahedral environment, and two Fe(III) ions are bridged by the methoxyl oxygens. Cryomagnetic analyses indicated a moderate antiferromagnetic interaction between the high‐spin Fe(III) ions, with J = ? 27.05 cm^?1. Moreover, the binding interaction of DNA with the diiron complex was investigated by spectroscopic and agarose gel electrophoretic methods, showing moderate cleavage activity on pBR322 plasmid DNA at physiological pH and temperature. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis,crystal structure,and antibacterial activity of mononuclear nickel(II) and cobalt(III) Schiff-base complexes

Four new mononuclear complexes, [Ni(L¹)(NCS)₂] (1), [Ni(L²)(NCS)₂] (2), [Co(L¹)(N₃)₂]ClO₄ (3), and [Co(L²)(N₃)₂]ClO₄ (4), where L¹ and L² are N,N′-bis[(pyridin-2-yl)methylidene]butane-1,4-diamine and N,N′-bis[(pyridin-2-yl)benzylidene]butane-1,4-diamine, respectively, have been prepared. The syntheses have been achieved by reaction of the respective metal perchlorate with the tetradentate Schiff bases, L¹ and L², in presence of thiocyanate (for 1 and 2) or azide (for 3 and 4). The complexes have been characterized by microanalytical, spectroscopic, single crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that 1–4 are distorted octahedral geometries. The antibacterial activity of all the complexes and their constituent Schiff bases have been tested against Gram-positive and Gram-negative bacteria.     

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 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.     

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.     

Synthesis,crystal structure,magnetism, and biological activities of an oxo-bridged diiron(III) complex

An unsymmetrical oxo-bridged diiron(III) complex [Fe₂L₂(μ-O)], {H₂L?=?trans-N,N′-bis-(2hydroxy-1-naphthalidehydene)-cyclohexanediamine} has been synthesized and characterized by various physico-chemical techniques. In the complex, each deprotonated bi-anionic L^2? serves as a terminal tetradentate ligand (N₂O₂) and coordinates to one Fe to form a [FeL]⁺ unit. Two [FeL]⁺ units are further linked by an oxo-bridge to construct the binuclear oxo-Fe species with intramolecular Fe–Fe separation of 3.38?Å. Variable-temperature magnetic susceptibility studies revealed a strong antiferromagnetic interaction between two iron centers with J of ?112?cm^?1. The interaction of the complex with CT-DNA was studied by various spectroscopic and viscosity measurements, which indicated that the complex could interact with CT-DNA through intercalation. In addition, the complex is able to cleave pBR322 DNA in the presence of H₂O₂. Furthermore, the interaction of the compound with BSA was also investigated, which indicated that the complex could quench the intrinsic fluorescence of BSA by a static quenching mechanism.     

Synthesis,crystal structure,magnetic property and DNA cleavage activity of a new terephthalate-bridged tetranuclear copper(II) complex

A new terephthalate-bridged tetranuclear copper(II) complex has been synthesized and structurally characterized by X-ray crystallography: [Cu₄(L)₂(tp)(dmf)₂] (1) (H₃L = 1,3-bis(salicylideneamino)propan-2-ol, tp = terephthalate and dmf = N,N′-dimethylformamide). The dinucleating pentadentate character of the ligand (H₃L) and the desired pair-of-dimers arrangement, through the incorporation of the bridging terephthalate moiety, is clearly evident from the structure of 1. The copper atoms are coordinated in a slightly distorted square pyramidal arrangement within each dinucleating half of the complex and are bridged mono-atomically by the secondary alkoxo oxygen of the ligand and di-atomically by the terephthalate moiety. The apical position is occupied by the oxygen atom of the dmf. The structure of 1 reveals a short intramolecular Cu–Cu separation (ca. 3.1 Å), in combination with long intramolecular copper separations (ca. 11 Å). The variable temperature-dependent susceptibility measurement (2–300 K) of 1 reveals a dominant ferromagnetic coupling, 2J = 18.70 cm⁻¹. Complex 1 binds to double-stranded CT (calf-thymus) DNA giving a K_app value of 1.25 × 10⁷ M⁻¹ and displays efficient cleavage of supercoiled pUC19 DNA in the presence of H₂O₂ following a hydroxyl radical pathway.     

Synthesis,crystal structure,and magnetic properties of a linear trinuclear Cu(II) complex

A new linear trinuclear Cu(II) complex, [Cu₃(NTA)₂(4,4′-bpt)₄(H₂O)₂]?·?10H₂O (H₃NTA?=?nitrilotriacetic acid, 4,4′-bpt?=?4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole) (1), was obtained from evaporation of an aqueous solution containing Cu(NO₃)₂?·?6H₂O, 4,4′-bpt, nitrilotriacetic acid (H₃NTA), and NaOH. 1 was characterized using single-crystal X-ray diffraction, IR, and elemental analysis. In the trimer, the three linear copper ions are bridged by two NTA carboxylate groups in a syn–anti conformation and connected by 4,4′-bpt to produce a 1-D array. Temperature-dependent magnetic susceptibilities reveal the presence of weak antiferromagnetic exchange between metal centers.     

Synthesis,structure, DNA binding and cleavage ability of a new copper ciprofloxacin complex

The structure of 1 consists of [Cu(HCp)(phen)(H₂O)]²⁺ (HCp is ciprofloxacin and phen is 1,10-phenanthroline), two acetates, and four free water molecules. In each cation, copper displays a distorted square pyramid, coordinated to ring 3-carboxylate and 4-oxo oxygen from HCp, two nitrogens from phen, and one water molecule. There are five water molecules in each discrete complex with one coordinated to Cu center, and the other four linked to each other by intermolecular hydrogen bonds. Two uncoordinated acetates make the compound neutral. The complex exhibits higher DNA binding compared to HCp at the same conditions by fluorescence and viscosity measurements. Combining its structure with the DNA-binding result, the binding mechanism may be explained by intercalation. Moreover, 1 shows significant cleavage of DNA in the presence of a reducing agent, such as ascorbate by gel electrophoresis using supercoiled pBR322 DNA in Tris-HCl buffer (pH 7.4). The complex also has a higher activity against Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Klebsiella pneumoniae than HCp.     

Synthesis,crystal structure and magnetic properties of N -benzesulfonyl-L-glutamic acid-bridged binuclear nickel(II) complex

N-benzesulfonyl-L-glutamic acid-bridged binuclear nickel(II) complex, [Ni₂(Bs-Glu)₂(bipy)₂ (H₂O)₂]?·?3H₂O (Bs-Glu?=?N-benzesulfonyl-L-glutamic acid dianion, bipy?=?2,2′-bipyridine), has been synthesized and characterized structurally and magnetically. It crystallizes in the triclinic space group P 1. The α-carboxyl group coordinates to Ni(II) in a monodentate mode, while the γ-carboxyl group coordinates in a chelating mode. In the temperature range 2–300?K, magnetic measurements show that the exchange interaction of the two Ni(II) ions is antiferromagnetic, and the values for J, g are ?2.47?cm^?1 and 2.18, respectively.