599,043 research outputs found
Ring opening polymerization of lactides and lactones by multimetallic alkyl zinc complexes derived from the acids Ph₂C(X)CO₂2H (X = OH, NH₂ )
The reaction of the dialkylzinc reagents R₂Zn with the acids 2,2-Ph₂C(X)(CO₂H), where X = NH₂, OH, i.e. 2,2′-diphenylglycine (dpgH) or benzilic acid (benzH2), in toluene at reflux temperature afforded the tetra-nuclear ring complexes [RZn(dpg)]₄, where R = Me (1), Et (2), 2-CF₃C₆H₄ (3), and 2,4,6-F₃C₆H₂ (4); complex 2 has been previously reported. The crystal structures of 1·(2MeCN), 3 and 4·(4(C₇H₈)·1.59(H₂O)) are reported, along with that of the intermediate compound (2-CF₃C₆H₄)3B·MeCN and the known compound [ZnCl₂(NCMe)₂]. Complexes 1–4, together with the known complex [(ZnEt)₃(ZnL)₃(benz)₃] (5; L = MeCN), have been screened, in the absence of benzyl alcohol, for their potential to act as catalysts for the ring opening polymerization (ROP) of ε-caprolactone (ε-CL), δ-valerolactone (δ-VL) and rac-lactide (rac-LA); the co-polymerization of ε-CL with rac-LA was also studied. Complexes 3 and 4 bearing fluorinated aryls at zinc were found to afford the highest activities
Bis(2,3,5,6-tetra-2-pyridylpyrazine-κ3 N 2,N 1,N 6)nickel(II) dithiocyanate dihydrate
In the title compound, [Ni(C24H16N6)2](NCS)2·2H2O, the central NiII ion is octahedrally coordinated by six N atoms of two tridentate 2,3,5,6-tetra-2-pyridylpyrazine ligands (tppz). Two thiocyanate anions act as counter-ions and two water molecules act as solvation agents. O—H⋯N hydrogen bonds are observed in the crystral structure
ARPES Spectral Function in Lightly Doped and Antiferromagnetically Ordered YBa2Cu3O{6+y}
At doping below 6% the bilayer cuprate YBa2Cu3O{6+y} is a collinear
antiferromagnet. Independent of doping the value of the staggered magnetization
at zero temperature is about 0.6\mu_B. This is the maximum value of the
magnetization allowed by quantum fluctuations of localized spins. In this low
doping regime the compound is a normal conductor with a finite resistivity at
zero temperature. These experimental observations create a unique opportunity
for theory to perform a controlled calculation of the electron spectral
function. In the present work we perform this calculation within the framework
of the extended t-J model. As one expects the Fermi surface consists of small
hole pockets centered at (\pi/2,\pi/2). The electron spectral function is very
strongly anisotropic with maximum of intensity located at the inner parts of
the pockets and with very small intensity at the outer parts. We also found
that the antiferromagnetic correlations act against the bilayer
bonding-antibonding splitting destroying it. The bilayer Fermi surface
splitting is practically zero
Furanocoumarin compounds isolated from Dorstenia foetida potentiate irinotecan anticancer activity against colorectal cancer cells
Although the anticancer activity of Dorstenia foetida was already observed, the chemical entity responsible for this activity remained unidentified. In this study, the cytotoxic activity of two furanocoumarin compounds, i.e., 5-methoxy-3-(3-methyl-2,3-dihydroxybutyl)-psoralen (1) and 5-methoxy-3-(3-methyl-2,3-dihydroxybutyl)-psoralen diacetate (2) isolated from ethyl acetate fraction of D. foetida (whole plant) was investigated in several cancer cell lines including HN22, MDA-MB-231, HCT116, and HT29. The results revealed that compound 2 exhibited cytotoxic activity, particularly against colorectal cancer cell lines HCT116 and HT29. The interplay between compound 2 and irinotecan (Iri) showed synergism against HCT116, which was analyzed by CompuSyn software. The simulation revealed that, at the molar ratio of Iri:2 of 1:40, the concentration predicted to achieve a 90 % inhibitory effect when used in the combination would be ~28- and ~4-fold lower than the concentration of compound 2 and Iri, resp., when used individually. Finally, the percentage of apoptotic cells in the HCT116 line treated with the combination was markedly higher than in the cells treated with the individual agent (60 % apoptotic cells for the combination compared to 17 and 45 % for Iri and compound 2 monotherapy, resp). In conclusion, our results identified compound 2 as a plant-derived compound exhibiting anticancer properties that can act synergistically with Iri and warranted further research to assess the potential of this synergism for colorectal cancer treatment
N,N-Dimethylethane-1,2-diaminium bis(3-hydroxybenzoate)
In the title compound, C4H14N2
2+·2C7H5O3
−, both the N,N-dimethylethylenediamine N atoms are protonated and two 3-hydroxybenzoate anions act as counter-ions. In the crystal, anions and cations are linked by a network of N—H⋯O and O—H⋯O hydrogen bonds
Bis(2,3,5,6-tetra-2-pyridylpyrazine-κ3 N 2,N 1,N 6)iron(II) bis(dicyanamidate) 4.5-hydrate
In the title compound, [Fe(C24H16N6)2][N(CN)2]2·4.5H2O, the central iron(II) ion is hexacoordinated by six N atoms of two tridentate 2,3,5,6-tetra-2-pyridylpyrazine (tppz) ligands. Two dicyanamide anions [dca or N(CN)2
−] act as counter-ions, and 4.5 water molecules act as solvation agents. The structure contains isolated cationic iron(II)–tppz complexes and the final neutrality is obtained with the two dicyanamide anions. One of the dicyanamide anions and a water molecule are disordered with an occupancy ratio of 0.614 (8):0.386 (8). O—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds involving dca, water and tppz molecules are observed
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