Six‐coordinated vanadium(IV) complexes with tridentate task‐specific ionic liquid Schiff base ligands: Synthesis,characterization and effect of ionic nature on catalytic activity

By reaction of 5‐(chloromethyl)salicylaldehyde with triphenylphosphine and N‐methylimidazole in two separate reactions, salicylaldehydetriphenylphosphonium chloride (S²) and salicylaldehydemethylimidazolinium chloride (S³) were prepared. Reaction of 2‐(aminomethyl)pyridine with these aldehydes resulted in the task‐specific ionic liquid Schiff base ligands L¹ and L², respectively. Then six‐coordinated vanadium(IV) Schiff base complexes of VO(acac)L^1–4 were synthesized by reactions of these tridentate Schiff base ligands and VO(acac)₂ in 1:1 stoichiometry. The aldehydes, ligands and VO(acac)L^1–4 complexes were characterized using infrared, ¹H NMR, ¹³C NMR, ³¹P NMR, UV–visible and mass spectroscopies, as well as elemental analysis. Paramagnetic property of the complexes was also studied using magnetic susceptibility measurements. The complexes were used as catalysts in epoxidation of cyclooctene and oxidation of methylphenyl sulfide and the reaction parameters were optimized. The effect of the ionic nature of the complexes was investigated in these oxidation reactions. The catalytic activity of the complexes could be varied by changing the ionic (cationic or anionic) character of VO(acac)L^1–4 catalysts in which counter anion variation showed a greater effect than cationic moiety variation.     

Synthesis,characterization and antimicrobial activities of triorganotin(IV) complexes with azo-azomethine carboxylate ligands: crystal structure of a tributyltin(IV) and a trimethyltin(IV) complex

Triorganotin(IV) complexes with polyaromatic azo-azomethine carboxylate ligands viz. 2-{4-hydroxy-3-[(2/4-hydroxyphenylimino)methyl]phenylazo}benzoic acids [H₃L¹/H₃L²] were synthesized by reacting the ligands with either bis-tri-n-butyltin(IV) oxide (for 1 and 4) or trimethyltin(IV) chloride in presence of triethylamine (for 2 and 5) or triphenyltin(IV) hydroxide (for 3 and 6). The complexes were characterized by elemental analysis, UV, IR, NMR, and mass spectrometry. NMR spectroscopic studies of the compounds suggested that the complexes adopt four-coordinate tetrahedral geometry around tin in solution. Molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction. Both complexes have distorted trigonal bipyramidal geometry around tin in the solid state. Compound 1 is a one-dimensional (1-D) double chain coordination polymer which can be described as two different 24- and 30-membered non-porous macrocyclic rings constructed from two tributyltin units and two ligand moieties. The structure of 2 comprises a discrete cyclic centrosymmetric dimer with two lattice water molecules per formula unit. In the dimer, two trimethyltin entities are bridged by two ligand moieties. The dimers are further interconnected with lattice water molecules by multiple O–H?O hydrogen bonds to form a 1-D H-bonded network. The complexes were also screened for their antimicrobial activities.     

Synthesis,characterization, equilibria and biological activity of dimethyltin(IV) complex with 1,4-piperazine

The interaction of dimethyltin(IV) dichloride (DMT) with 1,4-piperazine (PIP) was investigated. The complex formation equilibria of the complexes formed in solution were investigated. The stoichiometry and stability constants of the complexes formed in solution phase were determined at different temperatures and in solutions of dioxane–water mixtures of different dielectric constants. The equilibrium constant for the displacement of piperazine coordinated to dimethyltin(IV) by inosine as a representative of DNA was calculated. (DMT)(PIP)·3H₂O was synthesized and characterized by elemental analysis, spectral, and thermal techniques. The antitumor activity of the complex was screened.     

Synthesis and structural characterization of Pd(II) thiosemicarbazonato complex: Catalytic evaluation in synthesis of diaryl ketones from aryl aldehydes and arylboronic acids

A simple route to synthesize triphenylphosphinopalladium(II) thiosemicarbazonato complex has been described. Elemental analysis, spectral (IR, NMR) and single crystal X-ray diffraction techniques were employed for the complete characterization of the complex. The latter was found to be effective catalyst for carbon–carbon cross-coupling reaction of aryl- and heteroarylboronic acids with aromatic and heteroaromatic aldehydes to form the corresponding diaryl ketones. The influence of reaction parameters such as solvent, base, reaction temperature and catalyst loading was also investigated.     

Synthesis,characterization, and molecular recognition of sugar‐functionalized nanoparticles prepared by a combination of ROP,ATRP, and click chemistry

The aim of this work was to prepare nanoparticles bearing sugar residues at their surface through the synthesis of amphiphilic block copolymer of poly d,l‐lactide (PLA) and poly(ethylene glycol)methacrylate, with the hydrophilic part terminating with glucopyranoside molecules as a model for any carbohydrate ligand. The construction was achieved by a combination of click chemistry, ring‐opening polymerization, and atom transfer radical polymerization. The modified monomer and resulting copolymer were characterized by NMR, SEC, and FTIR. Nanoparticles with a mean hydrodynamic diameter of <200 nm as determined by quasi‐elastic light scattering were prepared from the amphiphilic copolymer by nanoprecipitation using dimethylformamide (DMF) as water‐miscible solvent. In the range of 2.5–10 mg copolymer/mL DMF, the polymer concentration did not have much effect on the size of the nanoparticles. Accessibility of glucopyranoside molecules on the surface of the nanoparticles was confirmed by formation of aggregates from nanoparticles in the presence of concanavalin A observed by transmission electronic microscopy. Finally, no significant cytotoxicity toward human umbilical vein endothelial cells was detected for the final nanoparticles. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3178–3187, 2010     

Synthesis,characterization, and antimicrobial activities of a dinuclear copper(II) complex with bis(2-[(2-hydroxy-ethylimino)-methyl]-4,6-diiodo-phenol)

A dinuclear copper(II) complex with a newly synthesized tridentate Schiff-base ligand 2-[(2-hydroxy-ethylimino)-methyl]-4,6-diiodo-phenol (HL), of formula [Cu₂L₂Cl₂?·?C₄H₈O] (1), was prepared. Both the ligand and the complex were characterized by X-ray crystallography, confirming that the Schiff base is tridentate and its dinuclear copper(II) complex is five-coordinate from one nitrogen and two oxygens from L and two chlorides. The complex was assayed for antibacterial (Bacillus subtilis, Staphylococcus aureus, Streptococcus faecalis, Pseudomonas aeruginosa, Escherichia coli, and Enterobacter cloacae) activities by the MTT method. Complex 1 exhibited better antimicrobial activity than the ligand.     

A seven membered chelate ring complex of Mn(II) derived from bis(5-phenyl-2H-1,2,4-triazole)-3-yl-disulfane and cleavage of the S-S bond in a Co(II) complex: Synthesis, spectral and structural characterization

The reaction of Mn(OAc)₂·4H₂O with bis(5-phenyl-2H-1,2,4-triazole)-3-yl-disulfane (H₂ptds·2H₂O) (1) yielded new complex [Mn(ptds)(o-phen)₂] (2). It is observed that under similar conditions the reaction of Co(OAc)₂ with H₂ptds·2H₂O (1) leads to thermolysis of the S-S bond of the disulfane to yield [Co(pts)(o-phen)₂]·H₂O·0.5C₂H₅OH, with the newly generated organic ligand 5-phenyl-2H-1,2,4-triazole-3-sulfinate, (pts)²⁻. The ligand H₂ptds·2H₂O (1), [Mn(ptds)(o-phen)₂] (2) and [Co(pts)(o-phen)₂]·H₂O·0.5C₂H₅OH (3) crystallized into monoclinic, trigonal and triclinic crystal systems, respectively. The triazole ring nitrogen of the bidentate ligand chelates the Mn(II) center forming a seven membered chelate ring, while N, O donor sites of the resulting triazole sulfinate bond Co(II) to form a five membered chelate. The resulting complexes are paramagnetic and have a distorted octahedral geometry.     

Synthesis and characterization of a new layered organic-inorganic hybrid nickel(II) 1,4:5,8-naphthalenediimide bis-phosphonate, exhibiting canted antiferromagnetism, with Tc∼21 K

A new Ni(II) layered hybrid organic-inorganic compound of formula Ni₂[(NDI-BP)(H₂O)₂]·2H₂O has been prepared in very mild conditions from N,N′-bis(2-phosphonoethyl)napthalene-1,4:5,8-tetracarboximide (NDI-BP ligand) and NiCl₂. The X-ray powder structure characterization of the title compound suggests a pillared layered organic-inorganic hybrid structure. The distance between the organic and inorganic layers has been found to be 17.8 Å. The inorganic layers consist of corner sharing [NiO₅(H₂O)] octahedra and they are pillared by the diphosphonate groups. DC and AC magnetic measurements as a function of temperature and field indicate the presence of 2D antiferromagnetic exchange interactions between the nearest-neighbor Ni(II) ions below 100 K. A long-range magnetic ordering at T_c∼21 K has been established and is attributed to the presence of spin canting. AC magnetic measurements as a function of temperature at different frequencies confirm the occurrence of the magnetic ordering temperature at T=21 K and the presence of a slight structural disorder in the title compound.     

Synthesis and characterization of a new chloro-di-phenyltin(IV) complex with 2-mercapto-nicotinic acid: Study of its influence upon the catalytic oxidation of linoleic acid to hydroperoxylinoleic acid by the enzyme lipoxygenase

The complex [(C₆H₅)₂SnCl(HMNA)] (1) where H₂MNA is thioamide 2-mercapto-nicotinic acid has been synthesized by reacting a methanolic solution of di-chloro-di-phenyltin(IV) Ph₂SnCl₂ with an aqueous solution of 2-mercapto-nicotinic acid, containing twofold amount of potassium hydroxide. The Sn/ligand molar ratio is 2:1. The complex was characterized by elemental analysis, FT-IR and Mössbauer spectroscopic techniques. In addition the crystal structure of the molecule was determined by an X-ray diffraction at 293(2) K. C₁₈H₁₄ClNO₂SSn is monoclinic, space group P2₁/n, a = 15.089(3) Å, b = 15.846(3) Å, c = 16.691(3) Å, β = 105.57(3)°, Z = 8. The ligand coordinates to the metal center through the exocyclic sulfur and the heterocyclic nitrogen atoms, forming a four membered ring. The coordination sphere around the tin(IV) ion is completed with two carbon atoms from the two phenyl groups and one chlorine atom. The geometry around the tin atom can be described either as trigonal bipyramidal or tetragonal pyramidal. Finally, the influence of the complex [(C₆H₅)₂SnCl(HMNA)] (1) upon the catalytic peroxidation of linoleic acid to hydroperoxylinoleic acid by the enzyme lipoxygenase (LOX) was also kinetically and theoretically studied and the results compared with the ones of the corresponding binuclear complex [(C₆H₅)₃Sn(MNA)Sn(C₆H₅)₃ · (acetone)] (2) reported in the literature.     

Synthesis, characterization and biological evaluation of a novel Cu(II) complex with the mixed ligands 2,6-pyridinedicarboxylic acid and 2-aminopyridine

A novel bridged binuclear Cu(II) complex with mixed ligands, di-μ-(2-aminopyridine(N,N′))-bis[(2,6-pyridinedicarboxylate)aquacopper(II)] tetrahydrate, formulated as [Cu(μ-ap)(dipic)(H₂O)]₂·4H₂O (1) (dipic = 2,6-pyridinedicarboxylate, ap = 2-aminopyridine), has been synthesized and characterized by elemental, spectral (IR and UV–Vis.), thermal analysis, magnetic measurements and single crystal X-ray diffraction analysis. The central Cu(II) ion resides on a centre of symmetry in a distorted square-pyramid coordination environment comprising of two N atoms, one from dipic and one from the ap ring, two carboxylate O atoms from dipic, and one O atom from water. Intermolecular N–HO and O–HO hydrogen bonds and π–π stacking interactions seem to be effective in the stabilization of the crystal structure. The free ligands and the complex were also evaluated for their antimicrobial and radical scavenging activities (DPPH = 1,1-diphenyl-2-picrylhydrazyl hydrate) using in vitro microdilution methods. Antimicrobial screening of the free ligands and their complex showed that the free ligands and the complex possess antifungal activity against Candida sp.     

Insulin-like model complexes: Synthesis,spectra characterization and crystal structure of two novel oxovanadium complexes with poly(pyrazolyl)borate ligands VO(HB(pz)3)(H2B(pz)2) and VO(B(pz)4)2

Two new oxovanadium (IV) complexes VO(HB(pz)₃)(H₂B(pz)₂) (1) and VO(B(pz)₄)₂ (2) have been obtained by the reaction of oxovanadium sulfate with the corresponding ligands KHB(pz)₃, KH₂B(pz)₂ and KB(pz)₄, respectively. The two complexes were characterized by elemental analyses, IR, UV–Vis and X-ray diffraction. Complex 1 crystallizes in the orthorhombic space group, Pca2₁. Complex 2 crystallizes in the orthorhombic space group, Pna2₁. In both complexes, five nitrogen atoms and one oxygen atom coordinate to the vanadium atom, forming a distorted octahedral geometry (VON₅). In addition, related spectra characterization, hydrogen-binding properties, structural configuration and quantum chemistry calculations are also discussed.     

Synthesis,characterization, crystal structure and thermal analysis of a copper(II) mononuclear compound with 2,6- bis (3,5-dimethyl- N -pyrazolyl)pyridine (bdmpp) and selenocyanate as ligands

A single crystal of the copper(II) compound, [Cu(bdmpp)(SeCN)₂], 2, was obtained and its crystal structure was determined by X-ray diffraction methods. The complex was characterized by elemental, thermal and FTIR analysis. The FTIR analysis of the complex clearly shows the SeCN peaks at 2096 and 2061?cm^?1 which did not exist in the free organic ligand (bdmpp). X-ray analysis showed that 2 crystallized in the monoclinic space group P2₁/c. Cu(II) has a distorted trigonal bipyramidal coordination involving three N atoms from the ligand and two N atoms from the selenocyanate group.     

A 1D Cu(II) coordination polymer exhibiting ferromagnetic interactions and a mononuclear Cu(II) complex of substituted pyrazole carboxylic acids: Synthesis, characterization and crystal structure

Reaction of 2 equiv. amount of copper(II) nitrate hexahydrate with 1 equiv. of 5-methyl-1-pyridin-2-yl-1H-pyrazole-3-carboxylic acid (PyPzCA) in presence of triethyl amine base afforded a 1D coordination polymeric compound [Cu₂(PyPzCA)₂(H₂O)₃(NO₃)]NO₃·H₂O (1). Whereas, the same reaction when repeated with 1-(4,6-dimethyl-pyrimidin-2-yl)-5-methyl-1H-pyrazole-3-carboxylic acid (PymPzCA) instead of PyPzCA, a mononuclear compound [Cu(PymPzCA)]·2H₂O·NEt₃ (2) is formed. Both the complexes are crystallographically characterized. In 1, both the copper atoms (Cu1 and Cu2) have distorted square pyramidal geometry with N₂O₃ chromophore while, in 2, the central copper atom has a distorted trigonal bipyramidal geometry with N₄O chromophore. Complex 1, is a 1D coordination polymer where the metal centers being far apart and are involved in a weak ferromagnetic interaction which is quite unexpected.     

Synthesis, molecular and crystal structure of bis(triethanolamine)manganese(II) saccharinate: a seven-coordinate manganese complex with tri- and tetradentate triethanolamine ligands

The synthesis, molecular and crystal structure of bis(triethanolamine)Mn(II) saccharinate, [Mn(tea)₂](sac)₂ are reported. The configuration of the tea ligands results in an unusual example of coordination number seven for the Mn(II) ion. The two triethanolamine (tea) ligands coordinate to the Mn(II) ion forming a monocapped trigonal prism geometry, in which one of the tea ligands behaves as a tridentate ligand, while the other one acts as a tetradentate donor. The free and coordinated hydroxyl hydrogens of the tea ligands are involved in hydrogen bonding with the amine nitrogen, carbonyl and sulfonyl oxygens of the neighbouring sac ions to form a three-dimensional infinite network. A weak π–π interaction between the phenyl rings of the sac ions also occurs.     

Synthesis and properties of nickel(ii) diiminodithiolate and diiminodisulfide N2S2-type complexes. New complexes with non-innocent ligands

The following two groups of nickel(ii) diiminodithiolate and diiminodisulfide N₂S₂-complexes were synthesized for the first time: (1) complexes with complete conjugation between all four donor centers, viz., compounds with non-innocent ligands, and (2) complexes containing a short conjugation system involving only two imino groups of the ligand. The complexes were studied by ¹H NMR, ESR, and UV spectroscopy, mass spectrometry, and electrochemistry. Solutions of glyoxal bis(2-mercaptoanil)nickel(ii) in DMF showed an ESR signal, which decreased with time, the processes being accompanied by an analogous change in the intensity of the absorption band at 931 nm. The electrochemical properties of this complex also change with time. The results of studies demonstrated that compounds with non-innocent ligands of this type were initially generated as classical diiminodithiolate structures, which were transformed into the ortho-iminothiosemiquinonate biradicals and then into oligomeric complexes both in solution (fast transformation) and in the solid state (slow transformation). Oligomeric structures of these compounds are stable for a long period of time.     

Synthesis and characterization of tris{2-(N,N-bis(diphenylphosphino) aminoethyl} amine derivatives: Application of a palladium(II) complex as a pre-catalyst in the Heck and Suzuki cross-coupling reactions

The polydendate bis(phosphino)amine, tris{2-(N,N-bis(diphenylphosphino)aminoethyl}amine 1 has been prepared in a single step from the reaction of tris(2-aminoethyl)amine with six equivalents of PPh₂Cl in the presence of NEt₃ in THF. Oxidation of 1 with aqueous H₂O₂, elemental sulfur or grey selenium gave the corresponding oxide, sulfide or selenide derivatives. [{(P(E)Ph₂)₂NCH₂CH₂}₃N] (E: 2a O, 2b S, 2c Se), respectively. Reaction of [{(PPh₂)₂NCH₂CH₂}₃N] with 3 equiv. of PdCl₂(cod) or PtCl₂(cod) gave the corresponding chelate complexes, [Pd₃Cl₆1] or [Pt₃Cl₆1]. The new compounds were fully characterized by NMR, IR spectroscopy and elemental analysis. The catalytic activity of the Pd(II) complex was tested in the Suzuki coupling and Heck reactions. The Pd(II) complex catalyzed the Suzuki coupling and Heck reaction affording biphenyls and stilbenes, respectively, in high yields.     

Synthesis,spectroscopic characterization (IR, 1H, 13C and 119Sn NMR,electrospray mass spectrometry) and toxicity of new organotin(IV) complexes with N,N′,O‐ and N,N′,S‐scorpionate ligands

New organotin(IV) derivatives containing the anionic ligands bis(3,5‐dimethylpyrazol‐1‐yl)dithioacetate [LCS₂]⁻ and bis(3,5‐dimethylpyrazol‐1‐yl)acetate [LCO₂]⁻ have been synthesized from reaction between (CH₃)₂SnCl₂ and lithium salts of the ligands. Mononuclear complexes of the type {[LCX₂](CH₃)₂SnCl} (X = S or O) have been obtained and fully characterized by elemental analyses and FT‐IR in the solid state and by NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy, conductivity measurements and electrospray ionization mass spectrometry in solution. The acute toxicity of new organotin(IV) derivatives on rat was studied, comparing their effect with those of dimethyltin chloride (CH₃)₂SnCl₂. The comparison of LD₅₀ of organotin(IV) complexes and (CH₃)₂SnCl₂ administered intraperitoneally, as a single dose, evaluated in vivo on rats, showed that toxicity decreases as follows: (CH₃)₂SnCl₂ > LCO₂ > LCS₂. The effect of these organotin(IV) complexes on DNA was evaluated in vitro and in vivo on rats treated with different doses of these compounds (1/20 LD₅₀ and 1/100 LD₅₀). The lymphocyte DNA status was assessed by the comet assay, a rapid and sensitive single‐cell electrophoresis technique, used to detect primary DNA damage in individual cells. After 36 h from the start of treatment the two new organotin(IV) derivatives induced a significant rise in comet assay parameters, indicating an increasing presence of damaged DNA. Copyright © 2005 John Wiley & Sons, Ltd.