Crystal structures and DNA-binding properties of PrIII complexes derived from 8-hydroxyquinoline-2-carboxaldehyde and three aroylhydrazines

Pr^III and three synthesized ligands, 8-hydroxyquinoline-2-carboxaldehyde-(benzoyl)hydrazone, 8-hydroxyquinoline-2-carboxaldehyde-(2′-hydroxybenzoyl)hydrazone, and 8-hydroxyquinoline-2-carboxaldehyde-(isonicotinyl)hydrazone, respectively, can form binuclear Pr^III complexes with 1?:?1 metal-to-ligand stoichiometry and nine-coordination at Pr^III indicated by X-ray crystal structural analyses. Ligands are dibasic tetradentate, binding to Pr^III through the phenolate oxygen, nitrogen of quinolinato unit, the C=N of methylene, and ^–O–C=N– enolized and deprotonated from O=C–NH– of the aroylhydrazone side chain. One DMF binds orthogonally to the ligand plane from one side to the metal ion, while another DMF and a bidentate nitrate simultaneously bind from the other. Dimerization of the monomeric unit occurs through the phenolate oxygen leading to a central planar four-membered (PrO)₂ ring. The crystal structures are similar to each other and to other nine-coordinate lanthanide complexes with geometry of distorted edge-sharing mono-capped square-antiprism of [LnL(NO₃)(DMF)₂]₂ (Ln = La^III, Nd^III, Sm^III, Eu^III, Tb^III, Dy^III, Ho^III, and Er^III) except for Yb^III with eight-coordinate Yb^III center with distorted edge-sharing dodecahedron of [YbL(NO₃)(DMF)]₂, derived from 8-hydroxyquinoline-2-carboxaldehyde and aroylhydrazines. The ligands and Pr^III complexes can bind to calf thymus DNA through intercalation with binding constants at 10⁵ M^?1 and probably be used as potential antitumor drugs.     

Synthesis,structure, protein binding,and cytotoxicity of zinc(II) complexes with tridentate NNO Schiff-base ligands

Mononuclear and trinuclear zinc(II) complexes (1 and 2) with tridentate NNO Schiff-base ligands (HL¹?=?N-2-pyridiylmethylidene-4-chloro-2-hydroxy-phenylamine, HL²?=?N-2-pyridiylmethylidene-2-hydroxy-5-chloro-phenylamine) have been synthesized and characterized by single-crystal X-ray diffraction and elemental analysis. The binding properties of zinc(II) complexes with calf thymus DNA (CT-DNA) and HSA were investigated by UV–visible, fluorescence, and circular dichroism spectra. The zinc(II) complexes bind significantly to CT-DNA by intercalation and bind to protein HSA through a static quenching mechanism. The in vitro cytotoxicity of the complexes on human tumor cells lines was assessed by 3-(4,5-dimathylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide, Hoechst 33258 staining experiments.     

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,characterization, and DNA-binding of Ln(III) complexes with 2-hydroxybenzylidene-2-phenylquinoline-4-carbonylhydrazone

2-Hydroxybenzylidene-2-phenylquinoline-4-carbonylhydrazone (H₂L) and five Ln(III) complexes, [Ln(H₂L)(NO₃)₂]NO₃ [Ln = La (1), Pr (2), Sm (3), Eu (4), and Tb (5)], have been synthesized and characterized by ¹H NMR, elemental analysis, conductivity measurements, mass spectra, IR spectra, and UV spectra. The interaction of these complexes with calf thymus DNA was investigated by UV absorption spectroscopy, fluorescence spectroscopy, circular dichroism spectroscopy and viscosity measurements. Results suggest that these complexes bind to DNA via groove binding.     

Low-dimensional compounds containing bioactive ligands. XXII. First crystal structure,cytotoxic activity and DNA and HSA binding of a zirconium(IV) complex with 8-hydroxyquinoline-2-carboxylic acid

A new zirconium(IV) complex, diaquabis(8-hydroxyquinoline-2-carboxylato-κ³N,O²,O⁸)zirconium(IV) dimethylformamide disolvate, [Zr(C₁₀H₅NO₃)₂(H₂O)₂]·2C₃H₇NO or [Zr(QCa)₂(H₂O)₂]·2DMF ( 1 ) (HQCaH is 8-hydroxyquinoline-2-carboxylic acid and DMF is dimethylformamide), was prepared and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray structure analysis. Complex 1 is a mononuclear complex in which the Zr^IV atoms sit on the twofold axis and they are octacoordinated by two N and six O atoms of two tridentate anionic QCa²⁻ ligands, and two aqua ligands. Outside the coordination sphere are two DMF molecules bound to the complex unit by hydrogen bonds. The structure and stability of complex 1 in dimethyl sulfoxide were verified by NMR spectroscopy. The cytotoxic properties of 1 and HQCaH were studied in vitro against eight cancer cell lines, and their selectivity was tested on the BJ-5ta noncancerous cell line. Both the complex and HQCaH exhibited low activity, with IC₅₀ > 200 µM. DNA and human serum albumin (HSA) binding studies showed that 1 binds to calf thymus (CT) DNA via intercalation and is able to bind to the tryptophan binding site of HSA (Trp-214).     

Synthesis,characterization and biological activities of mononuclear and binuclear Fe(III) complexes with some symmetric and unsymmetric Schiff-base ligands

A series of mononuclear and binuclear Fe(III) complexes of some new symmetrical and unsymmetrical Schiff bases containing quinoline derivatives were synthesized and characterized by elemental and thermal analysis, conductance measurements and IR spectra. In mononuclear complexes, the unsymmetric Schiff bases are monobasic tetradentate towards the Fe(III) ion. However, in binuclear complexes, the symmetric Schiff-base ligands behave as monobasic bidentate towards each Fe(III) ion. The structure of the solid complexes are discussed and based on magnetic susceptibility measurements, electronic and ESR spectral studies. The biological activities of the ligands and their complexes are reported.     

Synthesis and spectral studies of macrocyclic Cu(II) complexes by reaction of various diamines,copper(II) perchlorate and 1,4-bis(2-carboxyaldehyde phenoxy)butane

Six macrocyclic complexes, were synthesized by reaction of 1,4-bis(2-carboxyaldehyde phenoxy)butane and various amines and their copper(II) perchlorate complexes were synthesized by template effect reaction of 1,4-bis(2-carboxyaldehyde phenoxy)butane, Cu(ClO₄)₂?·?6H₂O and amines. The metal-to-ligand ratios were found to be 1?:?1. Cu(II) metal complexes are 1?:?2 electrolytes as shown by their molar conductivities (Λ_M) in DMF (dimethyl formamide) at 10^?3?M. The Cu(II) complexes are proposed to be square planar based on elemental analysis, FT–IR, UV–Vis, magnetic susceptibility measurements, molar conductivity measurements, and mass spectra.     

Synthesis,structures, and characterization of copper(II), nickel(II), and cobalt(III) metal complexes derived from an asymmetric bidentate Schiff-base ligand

An asymmetric bidentate Schiff-base ligand (2-hydroxybenzyl-2-furylmethyl)imine (L–OH) was prepared. Three complexes derived from L–OH were synthesized by treating an ethanolic solution of the appropriate ligand with an equimolar amount of metallic salt. Three complexes, Cu₂(L–O^?)₂Cl₂ (1), Ni(L–O^?)₂ (2) and Co(L–O^?)₃ (3), have been structurally characterized through elemental analysis, IR, UV spectra and thermogravimetric analysis. Single crystal X-ray diffraction shows metal ions and ligands reacted with different proportions 1?:?1, 1?:?2 and 1?:?3, respectively, so copper(II), nickel(II), and cobalt(III) have different geometries.     

Substituting group induced structural transformation from 1D zigzag chain to 2D grid network in cyano-bridged dimetallic complexes derived from Mn(Schiff-base) and [Cr(CN)5NO]: Synthesis, crystal structure and magnetic properties

Two cyano-bridged dimetallic complexes derived from Mn^III(Schiff-base) and [Cr^I(CN)₅NO]³⁻, [Mn(3-CH₃)salen]₃[Cr(CN)₅NO]·2.5H₂O (1) and [Mn(5-CH₃)salen]₆[Cr(CN)₅NO]₂·2CH₃OH·16H₂O (2) [salen = N,N′-ethylenebis (salicylideneiminato)dianion] were synthesized and characterized. The reaction conditions of the two complexes are identical. The substituting group (CH₃-) in the salen-type ligands gives different assembly styles for the two complexes, 1D zigzag chain for 1 while 2D grid network for 2. The magnetic investigation indicates the dominant antiferromagnetic interactions between the Mn(III) and Cr(I) mediated by the CN bridge. Due to the weak interchain antiferromagnetic interactions, no magnetic ordering phase was observed in complex 1. Interestingly, complex 2 showed the long range ferrimagnetic magnetic ordering with T_c = 9 K, in contrast to 1. Furthermore, the hysteresis loop confirms the nature of complex 2 as soft ferrimagnet.     

Synthesis,spectroscopic, thermal properties,Calf thymus DNA binding and quantum chemical studies of M(II) complexes

A new series of transition metal complexes of Cu(II), Co(II), Ni(II), Mn(II) and Cd(II) were prepared from the ligand of 5‐(4‐benzenesulfonic acid azo)‐2‐thioxo‐4‐thiazolidinone (H₂L). The M(II) complexes were structurally elucidated by elemental analysis, infrared spectra, spectral studies, thermal analysis, magnetic measurements and X‐ray diffraction analysis. Elemental analysis and IR result suggested the ligand was bonded to the metal ions in monobasic/neutral bidentate through the nitrogen atom of the hydrazone group and oxygen atom of carbonyl group. The bond length, bond angle, HOMO, LUMO and quantum chemical parameters were calculated to confirm the geometry of the ligand and the M(II) complexes. In vitro antimicrobial behavior of ligand (H₂L) and its M(II) complexes (1‐5) was screened with targeted bacterial and fungal strains. Spectroscopic (UV‐vis) technique was employed in order to study the binding mode and binding strength of the ligand (H₂L) and its M(II) complexes to Calf thymus DNA (CT‐DNA). Intercalation is the most possible mode of interaction of the ligand (H₂L) and its M(II) complexes with CT‐DNA and the determined binding constants. Molecular docking was used to predict the binding between the starts (4‐aminobenzenesulfonic acid (start 1) and 2‐thioxo‐4‐thiazolidinone (start 2)) and tautomers (A‐C) of ligand (H₂L) with the receptors of prostate cancer mutant (PDB code: 2Q7K) and breast cancer mutant (PDB code: 3HB5).     

Mononuclear Fe(III) and tetranuclear [Fe(III)Gd(III)]2 complexes with a Schiff-base ligand derived from the o-vanillin: Synthesis, crystal structures and magnetic properties

The mononuclear high-spin iron(III) complexes [Fe(3-MeOsalpn)Cl(H₂O)] (1) and [Fe(3-MeOsalpn)(NCS)(H₂O)]·0.5CH₃CN (2) and the tetranuclear oxo-bridged compound [{Fe(3-MeOsalpn)Gd(NO₃)₃}₂(μ-O)]·CH₃CN (3) [3-MeOsalpn²⁻ = N,N′-propylenebis(3-methoxysalicylideneiminate)] have been prepared and magneto-structurally characterised. The iron(III) ion in 1 and 2 is six-coordinated in a somewhat distorted octahedral surrounding with the two phenolate-oxygens and two imine-nitrogens from the Schiff-base building the equatorial plane and a water (1 and 2) and a chloro (1)/thiocyanate-nitrogen (2) in the axial positions. The neutral mononuclear units of 1 and 2 are assembled into centrosymmetric dinuclear motifs through hydrogen bonds between the axially coordinated water molecule of one iron centre and methoxy-oxygen atoms from the Schiff-base of the adjacent iron atom. The values of the intradimer metal-metal distance within the supramolecular dimers are 4.930 (1) and 4.878 Å (2). The tetranuclear of 3 can be described as two {Fe^III(3-MeOsalpn)} units connected through an oxo-bridge, each one hosting a [Gd^III(NO₃)₃] entity in the outer cavity defined by the two phenolate- and two methoxy-oxygen atoms. The values of the intramolecular Fe?Fe and Fe?Gd distances in 3 are 3.502 and 3.606 Å, respectively. The analysis of the magnetic data of 1-3 in the temperature range 1.9-300 K shows the occurrence of weak intermolecular antiferromagnetic interactions in 1 and 2 [J = −0.76 (1) and −0.75 cm⁻¹ (2) with the Hamiltonian defined as H = −JS_Fe1·S_Fe1] whereas two intramolecular antiferromagnetic interactions coexist in 3, one very strong between the two iron(III) ions (J₁) through the oxo bridge and the other much weaker between the iron(III) and the Gd(III) ions (J₂) across the double phenoxo oxygens [J₁ = −275 cm⁻¹ and J₂ = −3.25 cm⁻¹, the Hamiltonian being defined as H=-J₁S_Fe1·S_Fe1^′-J₂(S_Fe1·S_Gd1+S_Fe1^′·S_Gd1^′)]. These values are analysed in the light of the structural data and compared with those of related systems.     

1-(2′-Pyridylazo)-2-naphtholate complexes of ruthenium: Synthesis,characterization, and DNA binding properties

Reaction of 1-(2′-pyridylazo)-2-naphthol (Hpan) with [Ru(dmso)₄Cl₂] (dmso = dimethylsulfoxide), [Ru(trpy)Cl₃] (trpy = 2,2′,2″-terpyridine), [Ru(bpy)Cl₃] (bpy = 2,2′-bipyridine) and [Ru(PPh₃)₃Cl₂] in refluxing ethanol in the presence of a base (NEt₃) affords, respectively, the [Ru(pan)₂], [Ru(trpy)(pan)]⁺ (isolated as perchlorate salt), [Ru(bpy)(pan)Cl] and [Ru(PPh₃)₂(pan)Cl] complexes. Structures of these four complexes have been determined by X-ray crystallography. In each of these complexes, the pan ligand is coordinated to the metal center as a monoanionic tridentate N,N,O-donor. Reaction of the [Ru(bpy)(pan)Cl] complex with pyridine (py) and 4-picoline (pic) in the presence of silver ion has yielded the [Ru(bpy)(pan)(py)]⁺ and [Ru(bpy)(pan)(pic)]⁺ complexes (isolated as perchlorate salts), respectively. All the complexes are diamagnetic (low-spin d⁶, S = 0) and show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on all the complexes shows a Ru(II)–Ru(III) oxidation on the positive side of SCE. Except in the [Ru(pan)₂] complex, a second oxidative response has been observed in the other five complexes. Reductions of the coordinated ligands have also been observed on the negative side of SCE. The [Ru(trpy)(pan)]ClO₄, [Ru(bpy)(pan)(py)]ClO₄ and [Ru(bpy)(pan)(pic)]ClO₄ complexes have been observed to bind to DNA, but they have not been able to cleave super-coiled DNA on UV irradiation.     

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

A μ-oxo-di-μ-carboxylato-bridged iron(III) complex containing two tridentate nitrogen ligands, {[Fe₂(bpma)(bpea)(μ-CH₃COO)₂ μ-O)] · (ClO₄)₂ · 0.5CH₃OH} (1) (bpma = N, N-bis(2-pyridylmethyl)methyl-amine, bpea = N,N-bis(2-pyridylmethyl)ethylamine), has been synthesized and determined by X-ray diffraction. Complex 1 crystallizes in the monoclinic space group P2₁/c with a = 10.9434(12) Å, b = 23.118(3) Å, c = 15.8721(18) Å, β = 92.736(2)° and Z = 4. In 1, each Fe(III) has a distorted octahedral geometry with a N₃O₃ donor set. The Fe(III) atoms are bridged by two carboxyl groups and one μ-oxo oxygen with Fe1–Fe2 separation of 3.064 Å. Susceptibility data of 1 indicate strong intramolecular antiferromagnetic coupling of the high-spin Fe(III) atoms with J = ?121.0 cm^?1 and g = 2.04. The interaction with calf thymus DNA was investigated by UV absorption and fluorescent spectroscopy. Results show that the complex binds to ct-DNA with a moderate intercalative mode. The interaction between 1 and pBR322 DNA has also been investigated by submarine gel electrophoresis; the complex exhibits effective DNA cleavage activity in the absence of activating agents under similar physiological conditions.     

Mononuclear copper(II) complex with terpyridine and an extended phenanthroline base, [Cu(tpy)(dppz)]: Synthesis, crystal structure, DNA binding and cytotoxicity activity

The new dipyrido[3,2-a:2′,3′-c]phenazine (dppz) copper(II) complex, [Cu(tpy)(dppz)]²⁺, where tpy is 2,2′:6′,2″-terpyridine, has been prepared and fully characterized by spectroscopic methods and single-crystal X-ray diffraction. Its DNA binding and in vitro cytotoxicity have been also studied. The molecular structure shows a distorted trigonal bipyramidal CuN₅ coordination geometry around the copper atom. The bidentate dppz ligand binds in the equatorial plane, while tpy exhibits axial-equatorial bonding. The interaction of the complex with DNA has been investigated by electronic absorption, competitive fluorescence titration, linear dichroism, voltammetric techniques and a gel electrophoresis mobility shift assay. It is proposed that the binding mode of the complex to DNA is of an intercalation nature with the planar dppz ligands located between the base pairs of double-stranded DNA.An in vitro cytotoxicity study of the complex on human breast adenocarcinoma (MCF7) cell line by an MTT assay indicates that the title complex may have the potency to act as an effective anticancer drug, with an IC₅₀ value of 4.57 μM (3.62-5.77).     

Synthesis, DNA interaction and antibacterial activities of La(III) and Gd(III) complexes of Schiff base derived from o-vanillin and lysine

Two novel complexes, [La(HL)(H₂O)₂NO₃] · NO₃ · H₂O and [Gd(HL)(H₂O)₂NO₃] · NO₃ · H₂O, where HL is a Schiff base derived from o-vanillin and lysine, have been synthesized and characterized by elemental analysis, conductivity measurements, IR, ¹H NMR and thermogravimetric analyses (TGA). The Schiff base ligand behaves as a tetradentate, coordinating through azomethine nitrogen, phenolic oxygen and two carboxylic oxygen atoms. The interaction of these complexes with calf thymus DNA (CT-DNA) was also investigated by spectrometric titration and viscometric measurements. The faint hypochromism of the complexes in the absorption spectra, the remarkable reduction of fluorescence intensity of ethidium bromide (EB) bound DNA, together with a small decrease in the viscosity of the DNA suggest that a partial intercalation may be the preferred binding mode between these two complexes and DNA. The antibacterial activity testing revealed that the complexes and their precursor Schiff base show a weak to moderate activity against Bacillus subtilis, Staphylococcus aureus and Escherichia coli.      

Synthesis,characterization, and magnetochemical properties of two Mn4 clusters derived from 2-pyridinecarboxaldehyde Schiff base ligands

Two tetranuclear manganese complexes, [Mn₄(L¹)₆](ClO₄)₂?2.75H₂O (1) [HL¹ = 4-methyl-2-((pyridin-2-ylmethylene)amino)phenol] and [Mn₄(L²)₄(NO₃)₃(OH)]?pz?3H₂O (2) [HL² = (1H-pyrazol-1-yl)(pyridin-2-yl)methanol, pz = pyrazole], have been synthesized and characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, and magnetic measurements. The structural analysis revealed that the central manganese ion is linked with three apical manganese ions through six phenoxo-bridges creating a Mn₄O₆ core for 1; 2 has a cubane-like topology with the Mn(II) ions and the deprotonated oxygens from L² alternatively occupying vertices. The magnetic studies indicated a weak ferromagnetic coupling interaction (J = 0.48 ± 0.087 cm^?1, g = 2.00, θ = ?0.78 K) for 1 and a weak antiferromagnetic spin-exchange interaction (J₁ = ?0.50 ± 0.075 cm^?1, J₂ = ?0.13 ± 0.082 cm^?1, g = 1.98) between Mn(II) ions for 2. The magnetostructural correlations of the two Mn₄ clusters have been discussed tentatively.     

Synthesis,structure, and DNA binding of three reduced amino-acid Schiff-base zinc(II), nickel(II), and cadmium(II) complexes

Three new reduced amino-acid Schiff-base complexes, [Zn(HL)₂] · H₂O (1), [Ni(HL)₂] · H₂O (2), and [Cd(HL)₂] · H₂O (3), where H₂L is a reduced Schiff base derived from condensation of N-(2-hydroxybenzaldehyde) and L-histidine, have been synthesized and characterized by elemental analysis, UV-Vis absorption spectra and single crystal X-ray diffraction. Complexes 1–3 are isostructural. All metal centers are six-coordinate with O₂N₄ donor sets in slightly distorted octahedra. Unlike its Schiff-base counterpart, the deprotonated monoanionic ligand HL^? has a more flexible backbone and two HL^? are tridentate to one metal. Moreover, the binding interactions of these complexes with calf thymus DNA (CT-DNA) have been investigated by UV-Vis spectra and fluorescence quenching, which show that the complexes bind in an intercalative mode.     

Synthesis,crystal structure,DNA binding,and DNA cleavage of a zinc complex containing N,N-bis(2-pyridylmethyl)amine

A water-soluble zinc complex, [Zn(bpea)Cl₂] (1) (bpea?=?N,N-bis(2-pyridylmethyl)ethylamine), was prepared to serve as a nuclease mimic. The complex was characterized by X-ray, infrared, and UV spectroscopy. Interactions of the complex with calf thymus-DNA (ct-DNA) have been investigated by UV absorption and fluorescence spectroscopies; the mode of ct-DNA binding for 1 has been proposed. DNA cleavage activities by 1 were performed in the absence of external agents. The influences of different complex concentrations or reaction times on DNA cleavage were studied.     

X-ray crystal structure of a Cu(II) complex with the antiparasitic drug tinidazole,interaction with calf thymus DNA and evidence for antibacterial activity

Interaction of metal ions with biologically active molecules like 5-nitroimidazoles modulates their electronic environment and therefore influences their biological function. In the present work, an antiparasitic drug tinidazole (tnz) was selected and a Cu(II) complex of tnz [Cu₂(OAc)₄(tnz)₂] was prepared. A dinuclear paddle-wheel [Cu₂(OAc)₄(tnz)₂] was obtained by single-crystal XRD and further characterized by spectroscopic techniques and cyclic voltammetry. To understand the biological implications of complex formation, interaction of tnz and its complex was studied with calf thymus DNA, bacterial and fungal cell lines. Results of calf thymus DNA interaction using cyclic voltammetry indicate the overall binding constant (K^*) of Cu₂(OAc)₄(tnz)₂ [(59?±?6)?×?10⁴?M^?1] is ~17 times greater than that of tnz [(3.3?±?0.4)?×?10⁴?M^?1]. Minimum inhibitory concentration values suggest that [Cu₂(OAc)₄(tnz)₂] possesses better antibacterial activity than tnz on both bacterial strains, while the activity on a fungal strain was comparable.