Interactions of the human telomeric DNA with terbium-amino acid complexes

The human telomeric DNA can form four-stranded structures: the G-rich strand adopts a G-quadruplex conformation stabilized by G-quartets and the C-rich strand may fold into an I-motif based on intercalated C (.) C+ base pairs. There is intense interests in the design and synthesis of compounds which can target telomeric DNA and inhibit the telomerase activity. Here we report the thermodynamic studies of the two newly synthesized terbium-amino acid complexes bound to the human telomeric G-quadruplex and I-motif DNA which were studied by means of UV-Visible, DNA meltings, fluorescence and circular dichroism. These two complexes can bind to the human telomeric DNA and have shown different features on DNA stability, binding stoichiometry, and sequence-dependent fluorescence enhancement. To our knowledge, this is the first report to show terbium-amino acid complexes can interact with the human telomeric DNA.

Syntheses of chromium(III) complexes with Schiff-base ligands and their catalytic behaviors for ethylene polymerization

A series of chromium(III) complexes LCrCl3 (4a-c) bearing chelating 2,2'-iminodiphenyisulfide ligands [L = (2-ArMeC=NAr)(2)S] was synthesized in good yields from the corresponding ligands and CrCl3.(THF). Using modified methylaluminoxane (MMAO) as a cocatalyst, these complexes display moderate activities towards ethylene polymerization, and produce highly linear polyethylenes with broad molecular weight distribution. Polymer yields, catalyst activities and the molecular weights, as well as the molecular weight distributions of the polymers can be controlled over a wide range by the variation of the structures of the chromium(III) complexes and the polymerization parameters, such as Al/Cr molar ratio, reaction temperature and ethylene pressure.

Novel highly active binuclear neutral nickel and palladium complexes as precatalysts for norbornene polymerization

A series of binuclear neutral nickel and palladium complexes [(XC6H2CH=NC6H3-iPr(2))MRL](2) 4b-f (X=NO2, M=Ni, R=Ph, L=PPh3, 4b; X=H, M=Pd, R=Me, L=PPh3,4c; X=H,M=Pd, R=Me, L=Py, 4d; X=NO2,M=Pd, R=Me, L=PPh3, 4e; X=NO2, M=Pd, R=Me, L=Py, 4f) and [(C10H7CH=NC6H3-iPr(2))MRL](2) 8a-c (M=Ni, R=Ph, L=PPh3, 8a; M=Pd, R=Me, L=PPh3, 8b; M=Pd, R=Me, L=Py, 8c) have been synthesized and characterized. The structures of complexes 4e and 8b have also been confirmed by X-ray crystallographic analysis. With modified methylalummoxane (MMAO) as cocatalysts, these complexes and complex [(C6H3CH=NC6H3-iPr(2))NiPh(PPh3)](2) 4a are capable of catalyzing the addition polymerization of norbomene (NBE) with the high activity up to 2.3 x 10(8) g PNBE/(mol(M) h). The structure of complexes affects considerably catalytic activity towards norbomene polymerization. The polymers obtained with nickel complexes are soluble, while those obtained with palladium complexes are insoluble. Palladium complexes 4c, 4e and 8b bearing PPh3 ligands exhibit much higher activities than the corresponding complexes 4d, M and 8c bearing pyridine ligands under the same conditions.

Nickel complexes catalyzed Heck reaction of iodobenzene and methyl acrylate

Nickel appears the most promising for the replacement of palladium among the inexpensive transition metals for that it is active for Heck reaction and about 500 times cheaper than palladium. In this article, we describe our recent results in the area of nickel-catalyzed Heck vinylations. Main focus is on the influence of ligand concentration in different organic solvents and the effects of the addition of water. The conversion is high in NMP and increases with increasing of PPh3/Ni ratio; in ethanol and toluene the conversion presents a maximum value on Ni(PPh3)(2). The effect of the addition of water is sensitive to the concentration of PPh3 and the nature of solvent, it was well explained with the formation and transfer of the active species in the different solvent systems.

Syntheses, structure and ethylene polymerization behavior of beta-diiminato titanium complexes

A series of new titanium complexes bearing beta-diiminato ligands [(Ph)NC(R-1)CHC(R-2)N(Ph)](2)TiCl2 (4a: R-1 = R-2 = CH3; 4b: R-1 = R-2 = CF3; 4c: R-1 = Ph, R-2 = CH3; 4d: R-1 = Ph, R-2 = CF3) has been synthesized and characterized. X-ray crystal structures reveal that complexes 4a and 4c adopt distorted octahedral geometry around the titanium center. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 4a-d are active catalysts for ethylene polymerization, and produce high molecular weight polyethylenes. Catalyst activities and the molecular weights of polymers are considerably influenced by the steric and electronic effects of substituents on the catalyst backbone under the same polymerization condition. With the strong electron-withdrawing groups (CF3) at R-1 or/and R-2 position, complexes 4b and 4d show higher activities than complexes 4a and 4c, respectively.

Titanium complexes with novel triaryl-substituted phosphinimide ligands: Synthesis, structure and ethylene polymerization behavior

A series of titanium phosphinimide complexes [Ph2P(2-RO-C6H4)(2)TiCl2 (7, R = CH3; 8, R = CHMe2) and (PhP(2-Me2CHOC6H4)][THF]TiCl3 (9) have been prepared by reaction of TiCl4 with the corresponding phosphinimines under dehalosilylation. The structure of complex 9 has been determined by X-ray crystallography, and a solvent molecule THF was found to be coordinated with the central metal and the Ti-O bond was consistent with the normal Ti-O (donor) bond length. The complexes 7 and 8 displayed inactive to ethylene polymerization, and the complex 9 displayed moderate activity in the presence of modified methylaluminoxane (MMAO) or i-BU3Al/Ph3CB(C6F5)(4), and this should be partly attributed to coordination of THF with titanium and the steric effect of two iso-propoxyl. And catalytic activity up to 32.2 kg-PE/(mol-Ti h bar) was observed.

Syntheses and crystal structures of four new organotin complexes with Schiff bases containing triazole

Four new organotin complexes, namely [(Bu2Sn)(2)O(EtO)(L1)](2) (1), [(Bu2Sn)(2)O(EtO)(L2)](2) (2), [(Bu2Sn)(2)O(EtO)(L-3)](2) (3) and [Ph3Sn(L4)]center dot 0.5H(2)O (4), were obtained by reactions of Bu2SnO and Ph3SnOH with 4-phenylideneamino-3-methyl-1,2,4-triazole-5-thione (HL1), 4-furfuralideneamino-3-methyl-1,2,4-triazole-5-thione (HL2), 4-(2-thienylideneamino)-3-ethyl-1,2,4-triazole-5-thione (HL3) and 4-(3,5-di-t-butylsalicylideneamino)-3-ethyl-1,2,4-triazole-5-thione (HL4). Compounds 1-4 were characterized by elemental analysis, IR spectra and their structures were determined by single-crystal X-ray diffraction methods. Complexes 1-3 show similar structures containing a Sn4O4 ladder skeleton in which each of the exo tin atoms is bonded to the N atom of a corresponding thione-form deprotonated ligand. Complex 4 shows a mononuclear structure in which the tin atom of triphenyltin group is coordinated by the S atom of a thiol-form L4(-) anion.

Syntheses, structures and luminescence of silver(I) sulfonate complexes with PPh3 ligand

In this paper, four new luminescent silver(I) sulfonate complexes with PPh3, namely Ag(L1)(PPh3)(2) (1), Ag(L2)(PPh3)(3) (2), [Ag-2(L3)(PPh3)(4) (H2O)center dot 1.5CH(3)CN center dot 0.5H(2)O (3) and [Ag-4(L4)(PPh3)(10)]center dot 8H(2)O (4), where L1=p-toluenesulfonate, L2=1-naphthalenesulfonate, L3=3-carboxylate-4-hydroxybenzenesulfonate, L4=1, 3, 6, 8-pyrenetetrasulfonatc and PPh3=triphenylphosphine, have been synthesized and characterized. The crystal structures were determined by single-crystal X-ray diffraction method. Compounds 1, 2, 3 and 4 adopt discrete structures rather than polymeric structures. Compounds I and 2 show mononuclear structures while 3 and 4 are dinuclear and tetranuclear molecules, respectively. Moreover the numbers of PPh3 molecules coordinating to one silver center are two or three. The photoluminescent properties of 1, 2 and 3 are discussed.

Synthesis, structure and ethylene polymerization of group 4 complexes with phosphinoamide ligands

Group 4 complexes containing diphosphinoamide ligands [Ph2PNR](2)MCl2 (3: R = Bu-t, M = Ti; 4: R = Bu-t, M = Zr; 5: R = Ph, M = Ti; 6: R = Ph, M = Zr) were prepared by the reaction Of MCl4 (M = Ti; Zr) with the corresponding lithium phosphinoamides in ether or THF. The structure of [(Ph2PNBu)-Bu-t](2)TiCl2 (3) was determined by X-ray crystallography. The phosphinoamides functioned as eta(2)-coordination ligands in the solid state and the Ti-N bond length suggests it is a simple single bond. In the presence of modified methylaluminoxane or i-Bu3Al/Ph3BC(C6F5)(4), catalytic activity of up to 59.5 kg PE/mol cat h bar was observed.

Titanium and zirconium complexes with aminoiminophosphorane ligands

A series of titanium and zirconium complexes based on aminoiminophosphorane ligands [Ph2P(Nt-Bu)(NR)](2)MCl2 (4, M = Ti, R = Ph; 5, M = Zr, R = Ph; 6, M = Ti, R = SiMe3; 7, M = Zr, R = SiMe3) have been synthesized by the reaction of the ligands with TiCl4 and ZrCl4. The structure of complex 4 has been determined by X-ray crystallography. The observed very weak interaction between Ti and P suggests partial pi-electron delocalization through both Ti and P. The complexes 4-7 are inactive for ethylene polymerization in the presence of modified methylaluminoxane (MMAO) or i-Bu3Al-Ph3CB(C6F5)(4) under atmospheric pressure, and is probably the result of low monomer ethylene concentration and steric congestion around the central metal.

Glucose-lowering activity of amino acid-N-phosphonic acid oxovanadium complexes and its interaction with DNA

Vanadium has well-documented lowering glucose properties both in vitro and in vivo. The design of new oxovanadium(IV) coordination compounds, intended for use as insulin-enhancing agents in the treatment of diabetes mellitus, can potentially benefit from a synergistic approach, in which the whole complex has more than an additive effect from its component parts. Biological testing with oxovanadium(IV) organic phosphonic acid, for insulin-enhancing potential included acute administration, by oral gavage in streptozotocin (STZ) diabetic rats. The complexes of oxovanadium(IV) amino acid-N-phosphonic acid exhibit higher lowering glucose activity in vivo. The interaction of the complexes of oxovanadium(IV) amino acid-N-phosphonic acid with DNA was investigated by agarose gel electrophoresis. The results indicated that these complexes have strong interaction with DNA.

Synthesis, crystal structure, spectroscopy and electroluminescence of zinc(II) complexes containing bidentate 2-(2-pyridyl)quinoline derivative ligands

Three bidentate ligands, 4-phenyl-2-(2-pyridyl)-quinoline (ppq), 6-(carbazol-9-yl)-4-phenyl-2-(2-pyridyl)-quinoline (cpq) and 6-diphenylamino-4-phenyl-2-(2-pyridyl)-quinoline (dpq) and their zinc(II) complexes, have been designed and synthesized. The crystal structure of [Zn(ppq)(2)Cl]PF6 shows that the central zinc atom is coordinated with one chloride and four nitrogen atoms from two ligands. The introduction of an electron-donating substituent such as carbazole or an aromatic amine group at the 6-position of the quinoline moiety can generate colored tunable Zn complexes, and the photoluminescence (PL) wavelength was modulated from 418 nm for [Zn(ppq)(2)Cl]PF6 to 591 nm for [Zn(cpq)(2)Cl]PF6 and 638 nm for [Zn(dpq)(2)Cl]PF6 in CH2Cl2 solution. The electroluminescence spectrum of [Zn(dpq)(2)Cl]PF6 exhibits pure red light emission with the Commission Internationale de L'Eclairage (CIE) coordinates (0.63, 0.36) and a maximum at 648 nm.

New neutral nickel(II) complexes bearing pyrrole-imine chelate ligands: synthesis, structure and norbornene polymerization behavior

New neutral nickel(II) complexes bearing nonsymmetric bidentate pyrrole-imine chelate ligands (4a-d), [2-(ArNCH)C4H3N]Ni(PPh3)Ph [Ar=2,6-diisopropylphenyl (a), 2-methyl-6-isopropylphenyl (b), 2,6-diethylphenyl (c), 2-tert-butylphenyl (d)], have been prepared in good yields from the sodium salts of the corresponding ligands and trans-Ni(PPh3)(2)(Ph)Cl, and the structure of complex 4a has been confirmed by X-ray crystallographic analysis. These neutral Ni(II) complexes were investigated as catalysts for the vinylic polymerization of norbornene. Using modified methylaluminoxane (MMAO) as a cocatalyst, these complexes display very high activities and produce great mass polymers. Catalyst activity of up to 4.2 x 10(7) g (mol Ni h)(-1) and the viscosity-average molecular weight of polymer of up to 9.2 x 10(5) g mol(-1) were observed. Catalyst activity, polymer yield, and polymer molecular weight can be controlled over a wide range by the variation of reaction parameters such as Al-Ni ratio, norbornene-catalyst ratio, monomer concentration, polymerization reaction temperature and time.

Modified polyoxometalates: Hydrothermal syntheses and crystal structures of three novel reduced and capped Keggin derivatives decorated by transition metal complexes

Three novel polyoxometalate derivatives decorated by transition metal complexes have been hydrothermally synthesized. Compound 1 consists of [(PMo6Mo2V8O44)-Mo-VI-V-V-O-IV{CO (2,2'-bipy)(2)(H2O)}(4)](3+) polyoxocations and [(PMo4Mo4V8O44)-Mo-IV-V-V-O-IV{Co(2,2'-bipy)(2)(H2O)}(2)](3-) polyoxoanions, which are both built on mixed-metal tetracapped [PMo8V8O44] subunits covalently bonded to four or two {Co(2,2'-bpy)(2)(H2O)}(2+), clusters via terminal oxo groups of the capping V atoms. Compound 2 is built on [(PMo8V6O42)-V-VI-O-IV{Cu-I(phen)}(2)](5-) clusters constructed from mixed-metal bicapped [(PMo8V6O42)-V-VI-O-IV](7-) subunits covalently bonded to two {Cu(phen)}(+) fragments in the similar way to 1. The structure of 3 is composed of [(PMo9Mo3O40)-Mo-VI-O-V](6-) units capped by two divalent Ni atoms via four bridging oxo groups.

Hydrothermal synthesis, structure, and characterization of two one-dimensional chainlike hybrid complexes [(CuX)(2)(o-phen)](infinity) (X = Br, Cl; o-phen = o-phenanthroline)

Two novel organic-inorganic hybrid complexes [(CuX)(2)(o-phen)](infinity) (X = Br (1), Cl (2); o-phen = o-phenanthroline) have been synthesized hydrothermally and characterized structurally by elemental analyses, IR, ESR, XPS spectrum, TG analyses and single-crystal X-ray diffraction. Both title compounds exhibit novel one-dimensional chainlike copper halide scaffolding constructed by the unusual [Cu3X3] hexagon motifs by sharing opposite edges, where a single Cu site of each [Cu3X3] hexagon is chelated with N donors of o-phen group. To our knowledge, such basic o-phen-copper halide skeleton has not been reported hitherto. Moreover, TG analyses indicate that both title compounds possess high thermal stability.