Cu(II), Ni(II) complexes derived from chiral Schiff-base ligands: Synthesis, characterization, cytotoxicity, protein and DNA-binding properties.

A series of novel copper (II) and nickel (II) complexes derived from chiral Schiff-base ligands [(R)/(S)-H2L(1)=(R)/(S)-2-[(1-Hydroxymethyl-propylimino)-methyl]-5-methoxy-phenol and (R)/(S)-H2L(2)=(R)/(S)-2-[(1-Hydroxymethyl-2-phenyl-ethylimino)-methyl]-5-methoxy-phenol], were synthesized and characterized by elemental analyses, (1)H NMR spectra, FT-IR spectrum. The crystal structures of complexes 1-5 were determined through single crystal X-ray diffraction (SXRD). The structures showed the ligands coordinated to the Cu/Ni (II) ion in a neutral manner via ONO donor atoms, and oxygen atoms of solvent molecules occupy the axial positions in Ni (II) complexes 3 and 4. The complexes interactions with BSA and CT-DNA were investigated by various spectroscopic methods (UV-Visible, circular dichroism spectrum, fluorescence spectroscopic and synchronous fluorescence spectra). Interactions of chiral copper (II) complexes are stronger than nickel (II) complexes. Further, the cytotoxicities of the complexes 1-6 towards three kinds of cancerous cell lines, were human lung adenocarcinoma (A549), human cervical carcinoma cell (HeLa) and human breast cancer cell (MCF-7) respectively, were evaluated by MTT assay. All complexes exhibited good cytotoxic activity. Furthermore, Cu (II) complex 5 derived from (R)-Schiff-base ligand was found to be more effective towards HeLa cancerous cell. The results showed that chirality and metal ion have important influence on their anticancer activities and interactions with DNA/BSA.

Improved stability of (+)-catechin and (-)-epicatechin by complexing with hydroxypropyl-ß-cyclodextrin: Effect of pH, temperature and configuration.

The stability and bioavailability of catechins, a kind of tea polyphenols with health benefit, could be improved by complexing with cyclodextrins. The aim of this study was to investigate the complexation of two geometrical isomers, (+)-catechin and (-)-epicatechin, with hydroxypropyl-ß-cyclodextrin (HP-ß-CD) in tris-HCl buffer solutions at pH 6.8-8.0 using isothermal titration calorimetry, fluorescence and proton nuclear magnetic resonance spectroscopy. Experimental results showed that these inclusion interactions are primarily enthalpy-driven processes. The complexation constant (KC) of EC+HP-ß-CD complex was less than that of CA+HP-ß-CD at the same temperature and pH value. Temperature and pH studies showed that the KC value decreased with the rise of temperature and pH. Stability study indicated that HP-ß-CD showed a stronger protection effect on CA than that on EC. The different inclusion modes between CA and EC were discussed in terms of the discrepancy in their molecular structures.

Chiral manganese (IV) complexes derived from Schiff base ligands: Synthesis, characterization, in vitro cytotoxicity and DNA/BSA interaction.

Two new couples of chiral manganese (IV) complexes with Schiff-base ligands, Λ-[Mn(R-L(1))2]·2(CH3OH) (Λ-1) and Δ-[Mn(S-L(1))2]·2(CH3OH) (Δ-1), Λ-[Mn(R-L(2))2]·(H2O)2 (Λ-2) and Δ-[Mn(S-L(2))2]·(H2O)2 (Δ-2), {H2L(1)=(R/S)-(±)-1-[(1-hydroxymethyl-propylimino)-methyl]-naphthalen-2-ol, H2L(2)=(R/S)-(±)-1-[(1-Hydroxymethyl-2-phenyl-ethylimino)-methyl]-naphthalen-2-ol} have been synthesized, and fully characterized by elemental analyses, UV-Vis spectrum, circular dichroism spectrum, FT-IR spectrum, mass spectrum, and single crystal X-ray diffraction (SXRD). The interaction of the four chiral Mn (IV) complexes with CT-DNA and BSA were also investigated by various spectroscopic techniques (UV-visible, fluorescence spectroscopic). The results show that the Δ-complexes exhibit more efficient CT-DNA interaction with respect to the Λ-complexes. All the complexes could quench the intrinsic fluorescence of BSA by a static quenching process. In addition, the vitro cytotoxicity of these complexes toward four kinds of cancerous cell lines (A549, HeLa, HL-60, and Caco-2) was assayed by the MTT method, which exhibited to be selectively active against certain cell lines.

Crystal Structure, Cytotoxicity and Interaction with DNA of Zinc (II) Complexes with o-Vanillin Schiff Base Ligands.

Two new zinc complexes, Zn(HL1)2 (1) and [Zn2(H2L2)(OAc)2]2 (2) [H2L1 = Schiff base derived from o-vanillin and (R)-(+)-2-amino-3-phenyl-1-propanol, H3L2 = Schiff base derived from o-vanillin and 2-amino-2-ethyl-1,3-propanediol], have been synthesized and characterized by single crystal X-ray diffraction, elemental analyses, TG analyses, solid fluorescence, IR, UV-Vis and circular dichroism spectra. The structural analysis shows that complex 1 has a right-handed double helical chain along the crystallographic b axis. A homochiral 3D supramolecular architecture has been further constructed by intermolecular C-H··· π, O-H···O and C-H···O interactions. Complex 2 includes two crystallographically independent binuclear zinc molecules. The two binuclear zinc molecules are isostructural. The 2-D sheet supramolecular structure was formed by intermolecular hydrogen bonding interaction. The fluorescence of ligands and complexes in DMF at room temperature are studied. The interactions of two complexes with calf thymus DNA (CT-DNA) are investigated using UV-Vis, CD and fluorescence spectroscopy. The results show that complex 1 exhibits higher interaction with CT-DNA than complex 2. In addition, in vitro cytotoxicity of the complexes towards four kinds of cancerous cell lines (A549, HeLa, HL-60 and K562) were assayed by the MTT method. Investigations on the structures indicated that the chirality and nuclearity of zinc complexes play an important role on cytotoxic activity.

A comparative study of cytotoxicity and interaction with DNA/protein of five transition metal complexes with Schiff base ligands.

Five transition metal complexes NiL(1)2 (1), CuL(1)2 (2), ZnL(1)2 (3), [MnL(1)2(N3)]n·nCH2Cl2 (4), CuL(2)2 (5) {HL(1)=3-{[2-(2-hydroxy-ethoxy)-ethylimino]-methyl}-naphthalen-2-ol, HL(2)=2-{[2-(2-hydroxy-ethoxy)-ethylimino]-methyl}-phenol} have been synthesized and fully characterized. In all of the complexes, the ligands coordinated to the metal ion in a negative fashion via O and N donor atoms. The X-ray structures of nickel complex 1 and copper complexes 2 and 5 are four-coordinated monomers and show slightly distorted square-planar geometry in the vicinity of the central metal atom. Zinc complex 3 exhibits a four-coordinated tetrahedral structure. Differently, manganese complex 4 reveals a six-coordinated octahedral structure, one-dimensional chain is linked by azide in the end-to-end mode. In vitro cytotoxicity of these complexes to various tumor cell lines was assayed by the MTT method. The results showed that most of these metal-Schiff base complexes exhibited enhanced cytotoxicity than Schiff base ligands, which clearly implied a positive synergistic effect. Moreover, these complexes appeared to be selectively active against certain cell lines. The interactions of these metal complexes with CT-DNA were investigated by UV-vis, fluorescence and CD spectroscopy, the results indicated that these complexes are metallointercalators and can interact with CT-DNA. The study of interaction between complexes and BSA indicated that all of the complexes could quench the intrinsic fluorescence of BSA in a static quenching process.

Organotin(IV) complexes derived from Schiff base N'-[(1E)-(2-hydroxy-3-methoxyphenyl)methylidene]pyridine-4-carbohydrazone: synthesis, in vitro cytotoxicities and DNA/BSA interaction.

Five organotin(IV) compounds were synthesized from N'-[(1E)-(2-hydroxy-3-methoxyphenyl)methylidene]pyridine-4-carbohydrazone and the corresponding dialkyltin(IV) or trialkyltin(IV) precursor. Solid state structures were determined by IR, elemental analysis, NMR spectroscopy, and for 1, 2, 4 and 5 single crystal X-ray diffraction analysis. Compounds 1, 2 and 4 are monomers with the tin atoms five-coordinated in distorted trigonal bipyramid, of which the deprotonated Schiff base ligand chelate to tin center in the enolic tridentate mode. Differently, in compound 5, the enolization does not occur for the Schiff base ligand, and only the pyridinyl N atom and the deprotonated phenol hydroxyl oxygen atom participate in the coordination. Fascinatingly, six trimethyltin(IV) coordination units are linked by the Sn⋯N weak interaction atoms and form a 72-membered crown-like macrocycle. Preliminary in vitro cytotoxicity studies on five human tumor cells lines (HL-60, A549, HT-29, HCT-116 and Caco-2) by MTT assay reveal that di-n-butyltin(IV) complex 2 and diphenyltin(IV) complex 4 triggered significant antiproliferative effects in cultured tumor cells, and their cytotoxic activity correlates with intracellular organotin(IV) concentration. The interaction of the complexes with calf thymus DNA (CT-DNA) has been explored by absorption and emission titration methods, which revealed that complexes 2 and 4 interact with CT-DNA through groove-binding and partial intercalation of the extended planar ligand with the DNA base stack. Further, the albumin interactions of complexes 2 and 4 were investigated using fluorescence quenching spectra and synchronous fluorescence spectra. Studies reveal that di-n-butyltin(IV) complex 2 with higher cytotoxicity show stronger DNA/BSA interaction than diphenyltin(IV) complex 4.

Effect of structure and composition of nickel(II) complexes with salicylidene Schiff base ligands on their DNA/protein interaction and cytotoxicity.

Three new salicylidene Schiff base nickel(II) complexes [Ni(L(1))(CH3COOH)2]2 (1), [Ni2(L(1))2(CH3OH)] (2), [Ni(L(2))2]·3H2O (3) {H2L(1)=N,N'-bis(salicylidene)-3,6-dioxa-1,8-diaminooctane, HL(2)=2-ethyl-2-(2-hydroxybenzylideneamino)propane-1,3-diol} were synthesized and characterized fully by structural, analytical, and spectral methods. The single-crystal X-ray structures of complexes 1 and 2 exhibit the symmetrical ligands coordinated to the nickel(II) ion in a tetradentate fashion via ONNO donor atoms, while the unsymmetrical ligand L(2) presented a ONO tridentate coordination mode in complex 3. The nickel(II) ions lie in the six-coordinated octahedral environment for the mononuclear complexes 1 and 3, along with dinuclear complex 2. The interaction of the complexes with calf thymus DNA (CT-DNA) has been explored by absorption and emission titration methods, which revealed that complexes 1-3 could interact with CT-DNA through intercalation. The interactions of the complexes with bovine serum albumin (BSA) were also investigated using UV-Vis, fluorescence and synchronous fluorescence spectroscopic methods. The results indicated that all of the complexes could quench the intrinsic fluorescence of BSA in a static quenching process. Further, the in vitro cytotoxic effect of the complexes examined on cancerous cell lines such as human lung carcinoma cell line (A549), human colon carcinoma cell lines (HCT-116), human promyelocytic leukemia cells (HL-60) and colonic cancer cell line Caco-2 showed that all three complexes exhibited substantial cytotoxic activity.

Family of mixed 3d-4f dimeric 14-metallacrown-5 compounds: syntheses, structures, and magnetic properties.

An isomorphous family of mixed 3d-4f dodenuclear aggregates, {[Mn(III)8Ln4(Clshi)8(OAc)6(µ3-OCH3)2(µ3-O)2(CH3OH)12(H2O)2]·4CH3OH·xH2O)} (where Ln = Eu(III) (1), Gd(III) (2), Tb(III) (3), and Dy(III) (4); ClshiH3 = 5-chlorosalicylhydroxamic acid; x = 5 for 1 and 3; x = 6 for 2; x = 2 for 4), were synthesized and characterized. They were obtained from the reaction of ClshiH3 with Mn(OAc)2·4H2O and Ln(NO3)3·6H2O. These isomorphous mixed 3d-4f compounds represent a family of novel structures with lanthanide ions in the metallacrown (MC) ring. Each dodecanuclear aggregate contains two offset stacked 14-MC-5 units with M-N-O-M-N-O-Ln-O-N-M-O-N-M connectivity to capture one Ln(III) ion in the core of each MC. Two 14-MC-5 units are connected through O ions with four Mn ions and six O atoms arranged in a double Mn4O6 cubane. Magnetic measurement indicates that antiferromagnetic interactions are present between the metal ions. The Dy(III) analogue with high anisotropy and large spin shows slow magnetization relaxation at a direct-current field of 2 kOe.

Hexa-kis-(dimethyl sulfoxide-κO)nickel(II) bis-(2,2-dicyano-ethene-1,1-dithiol-ato-κS,S')nickelate(II).

The reaction of NiCl(2)·6H(2)O with sodium 2,2-dicyano-ethene-1,1-dithiol-ate [Na(2)(i-mnt)] in dimethyl sulfoxide produces the title complex, [Ni(C(2)H(6)OS)(6)][Ni(C(4)N(2)S(2))(2)]. There is half each of an [Ni(C(2)H(6)OS)(6)](2-) complex anion and an [Ni{(CH(3))(2)SO}(6)](2+) complex cation in the asymmetric unit. The i-mnt ligand coordinates in a bidentate manner to the Ni atom in the anion through the two chelating S atoms in an approximate square-planar geometry. The Ni atom in the complex cation has an octahedral coordination environment with six dimethyl sulfoxide mol-ecules as ligands.

1,1'-[(1E,11E)-5,8-Dioxa-2,11-diazo-nia-dodeca-1,11-diene-1,12-di-yl]dinaph-thal-en-2-olate.

The title compound, C(28)H(28)N(2)O(4), crystallizes in a zwitterionic form with deprotonated naphthol hy-droxy groups and protonated imine N atoms. The asymmetric unit contains one half-mol-ecule located on a twofold rotation axis. Intra-molecular N-H⋯O hydrogen bonds occur and the two bicyclic ring systems form a dihedral angle of 64.2 (1)°. In the crystal, weak inter-molecular C-H⋯O hydrogen bonds link the mol-ecules into layers parallel to the bc plane.

A novel 9-MC-3 and 15-MC-6 onset stacked metallacrown single-molecule magnet: synthesis and crystal structure.

A novel enneanuclear manganese complex, [Mn(9)O(4)(Mesao)(6)(MeO)(3)(O(2)CMe)(3)(OH)(MeOH)(2)]·2.5DMF [1; Me-saoH(2) = 2-hydroxyphenylethanone oxime], was synthesized. The structure of 1 contains an unusual [Mn(9)O(4)] core with an unprecedented defective "supertetrahedron" topology based on two parallel, onset stacked 9-MC-3 and 15-MC-6 metallacrown subunits. Magnetic studies indicate that 1 behaves as a single-molecule magnet.

Tris(ethyl-enediammonium) bis-[(2-amino-ethyl)ammonium] bis-[bis-(µ(5)-hydrogen phosphato)penta-µ(2)-oxido-deca-oxido-penta-molybdenum(VI)] deca-hydrate.

The title compound, (C(2)H(10)N(2))(3)(C(2)H(9)N(2))(2)[Mo(5)(HPO(4))(2)O(15)]·10H(2)O, was prepared under hydro-thermal conditions at pH 5.0. The structure contains mono- and diprotonated ethyl-enediamine cations, [Mo(5)O(15)(HPO(4))(2)](4-) anions and uncoord-in-ated water mol-ecules. The [Mo(5)O(15)(HPO(4))(2)](4-) hetero-poly-oxometallate anion is made up of five MoO(6) octa-hedra sharing an edge and forming a ring, which is closed by common corners of the terminal MoO(6) octa-hedron. The ring is topped on both sides by two slightly distorted PO(4) tetra-hedra, sharing three corners with three MoO(6) octa-hedra. The terminal oxygen atoms of the PO(4) units are protonated. Together with the anions, the water mol-ecules and the ethyl-enediammonium cations are involved in N-H⋯O and O-H⋯O hydrogen bonding, forming a three-dimensional supra-molecular network.

A new Schiff base nickel(II) complex: {5,5'-dihydr-oxy-2,2'-[o-phenyl-enebis(nitrilo-methyl-idyne)]diphenolato}nickel(II) methanol disolvate.

The monomeric title nickel(II) complex of a salicylaldimine, [Ni(C(20)H(14)N(2)O(4))]·2CH(3)OH, was obtained by the reaction of 2,4-dihydroxy-benzaldehyde and 1,2-phenyl-enediamine with nickel(II) acetate. The Ni(II) atom is coordinated by two N atoms [Ni-N = 1.839 (2) Å] and two O atoms [Ni-O = 1.8253 (19) Å] in an approximately square-planar geometry. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds link the mol-ecules into a chain along [001].

Bis(benzo-15-crown-5-κO)barium tetrakis-(isothio-cyanato-κN)cobaltate(II).

In the title compound, [Ba(C(14)H(20)O(5))(2)][Co(NCS)(4)], the Ba(II) and Co(II) ions are situated on twofold rotational axes, so asymmetric unit contains half each of the complex cations and anions. The Co(II) ion is coordinated by four N atoms [Co-N 1.83 (2), 1.95 (3) Å] in a distorted tetra-hedral geometry. The Ba(II) ion is coordinated by ten O atoms [Ba-O 2.766 (19)-2.859 (19) Å] from two benzo-15-crown-5 ligands in a sandwich-like configuration.

[5,5'-Dihydr-oxy-2,2'-[o-phenyl-enebis(nitrilo-methyl-idyne)]diphenolato}copper(II) methanol disolvate.

In the title compound, [Cu(C(20)H(14)N(2)O(4))]·2CH(3)OH, the Cu(II) ion is coordinated by two N [Cu-N = 1.933 (2) and 1.941 (2) Å] and two O [Cu-O = 1.890 (2) and 1.9038 (19) Å] atoms from the tetra-dentate Schiff base ligand 5,5'-dihydr-oxy-2,2'-[o-phenyl-enebis(nitrilo-methyl-idyne)]diphen-olate (L) in a distorted square-planar geometry. In the crystal, inter-molecular O-H⋯O hydrogen bonds link two CuL mol-ecules and four solvent mol-ecules into a centrosymmetric cluster. The crystal packing exhibits short inter-molecular C⋯C contacts of 3.185 (4) and 3.232 (4) Å.

Bis{µ-1-[(2-oxidophen-yl)imino-meth-yl]-2-naphtholato}bis-[pyridine-copper(II)].

The dinuclear title complex, [Cu(2)(C(17)H(11)NO(2))(2)(C(5)H(5)N)(2)], consists of centrosymmetric dimers in which the Cu(II) atom displays an elongated square-pyramidal coordination geometry. The conformation of the dimer is stabilized by inter-molecular C-H⋯O hydrogen bonds and by π-π aromatic stacking inter-actions involving the pyridine and benzene rings with centroid-centroid separations of 3.624 (3) Å.

(1-{2-[2-(2-Ammonio-ethyl-amino)ethyl-amino]ethyl-imino-meth-yl}-2-naphtholato-κO,N,N',N'')chloridocopper(II) chloride.

In the square-pyramidal title complex, [CuCl(C(17)H(24)N(4)O)]Cl, the Cu(II) atom is coordinated by three N atoms [Cu-N 1.946 (2), 2.010 (2), 2.085 (3) Å], one O atom [Cu-O 1.910 (2) Å] and one apical Cl atom [Cu-Cl 2.6437 (9) Å]. The three coordinated N and one O atom are almost coplanar, with a maximum deviation of 0.0268 Å. The tetra-dentate ligand forms two five-membered (N-Cu-N) and one six-membered (N-Cu-O) chelate rings with bite angles of 84.06 (10), 85.30 (10) and 91.70 (9)°, respectively. The two N-Cu-N chelate rings are non-planar.

Bis[2-(2-hydroxy-3-meth-oxy-phen-yl)benzimidazolium] tetrachlorido-cuprate(II) methanol disolvate.

In the title compound, (C(14)H(13)N(2)O(2))(2)[CuCl(4)]·2CH(4)O, the geometry of the CuC1(4) (2-) ions (Cu site symmetry 2) is inter-mediate between tetra-hedral and square-planar. The dihedral angle between the benzimidazole and benzene ring systems is 8.74(14)°. A network of N-H⋯O, N-H⋯Cl and O-H⋯Cl hydrogen bonds helps to consoldiate the structure. Aromatic π-π stacking inter-actions involving the benzimidazole ring system, with a centroid-centroid distance of 3.785 (3) Å, also occur.