Nelson G. Fernandes

Correlation between DNA interactions and cytotoxic activity of four new ternary compounds of copper(II) with N-donor heterocyclic ligands.

Four new ternary complexes of copper(II) were synthesized and characterized: [Cu(hyd)(bpy)(acn)(ClO4)](ClO4)] (1), [Cu(hyd)(phen)(acn)(ClO4)](ClO4)] (2), [Cu(Shyd)(bpy)(acn)(ClO4)](ClO4)] (3) and [Cu(Shyd)(phen)(acn)(ClO4)](ClO4)] (4), in which acn=acetonitrile; hyd=2-furoic acid hydrazide, bpy=2,2-bipyridine; phen=1,10-phenanthroline and Shyd=2-thiophenecarboxylic acid hydrazide. The cytotoxic activity of the complexes in a chronic myelogenous leukemia cell line was investigated. All complexes are able to enter cells and inhibit cellular growth in a concentration-dependent manner, with an activity higher than that of the corresponding free ligands. The substitution of Shyd for hyd increases the activity, while the substitution of bpy for phen renders the complex less active. Therefore, the most potent complex is 4 with an IC50 value of 1.5±0.2μM. The intracellular copper concentration needed to inhibit 50% of cell growth is approximately 7×10(-15)mol/cell. It is worth notifying that a correlation between cytotoxic activity, DNA binding affinity and DNA cleavage was found: 1<3<2<4.

Experimental electron density of urea–phosphoric acid (1/1) at 100 K

The deformation electron density of the urea-phosphoric acid adduct has been studied from 100 K X-ray and neutron diffraction experiments. Data were interpreted according to the Hirshfeld model. The long hydrogen bonds show characteristics of electrostatic interaction. Deformation density maps on the short hydrogen bond shows hydrogen more strongly bonded to urea than to phosphoric acid, and peak maxima at almost midway between the two O-H bonds.

The chemical behaviour of di(2-pyridyl)sulphide, dps. Crystal and molecular structure of μ-di(2-pyridyl)sulphidebis(trans-dichlorotriethylphosphine platinum(II)), [{Pt(PEt3)Cl2}2μ-dps] and its reactivity towards stannylated species

The coordinating ability of the ligand di(2-pyridyl)sulphide, dps, was studied in several situations. Dps behaved as a bidentate chelating agent with SnX4 (X=Cl or Br) and also with Pd and Pt (PdCl2 and K2PtCl4), whereas with [Pt2(PR3)2Cl4], (R = Et or Ph), it formed bridging complexes: [{Pt(PR3)Cl2}2μ-dps]. The crystal and molecular structure of [{Pt(PEt3)Cl2}2μ-dps] was determined. This complex, as well as [M(dps)Cl2], (M = Pd or Pt), underwent reactions with SnCl2, which inserts into the M–Cl bonds producing heterobimetallic products, which are important in catalysis.

Nickel(II) complexes of dithiocarbimates from sulfonamides: syntheses and crystal structures

Abstract This work describes the syntheses of four compounds containing [Ni(RSO2NCS2)2]2− anions: (Bu4N)2[Ni(C6H5SO2NCS2)2] (1), (Bu4N)2[Ni(4-ClC6H4SO2NCS2)2] (2), (Bu4N)2[Ni(2-CH3C6H4SO2NCS2)2] (3) and (Bu4N)2[Ni(4-BrC6H4SO2NCS2)2] (4). They were obtained in the crystalline form by the reaction of the appropriate potassium N-R-sulfonyldithiocarbimate (RSO2NCS2K2) with nickel(II) chloride hexahydrate in methanol/water. Elemental analyses were consistent with the proposed formulae. UV–Vis and IR data are consistent with the formation of nickel–sulfur diamagnetic planar complexes. The 1H NMR and 13C NMR spectra showed the expected signals for the tetra-n-butylammonium cation and the dithiocarbimate moieties. Single crystal structure analyses showed that (Bu4N)2[Ni(2-CH3C6H4SO2NCS2)2] crystallizes in the triclinic space group P 1 , and (Bu4N)2[Ni(4-BrC6H4SO2NCS2)2] crystallizes in the monoclinic space group P21/c. In these compounds the Ni atom is coordinated to four S atoms in a distorted square plane geometry. The Ni and S atoms form a plane and NiS bonds are different from each other. In both compounds the Ni atoms are in the crystallographic center of symmetry.

Positron annihilation study in binary molecular solid solutions of metal acetylacetonate complexes using positron annihilation lifetime (PAL) and Doppler broadening (DBS) spectroscopies

Abstract PAL and DBS techniques have been used to study inhibition of positronium (Ps) formation in binary molecular solid solutions of Al(III) (tris)-acetylacetonate (acac), as matrix, and Co(III), Fe(III), Ru(III), Rh(III), and Ir(III) (tris)-acetylacetonates, as guest molecules. For all the studied systems, no Ps quenching reactions have been observed. For Al (1− x ) Co ( x ) (acac) 3 , Al (1− x ) Fe ( x ) (acac) 3 , and Al (1− x ) Ru ( x ) (acac) 3 systems, a strong inhibition of Ps formation was observed with increasing of guest molecule concentration. The obtained Ps yields measured by PAL were fitted by the Stern-Volmer equation. The DBS results confirm the inhibition constants ( k ) previously determined by PAL technique, except for the Al (1− x ) Ru ( x ) (acac) 3 system, where the experimental and calculated Doppler broadening curves are quite different. Only in Al (1− x ) Ir ( x ) (acac) 3 system, the inhiition effect was not detected. The highest total inhibition constants belong to Al (1− x ) Co ( x ) (acac) 3 and Al (1− x ) Ru ( x ) (acac) 3 systems and the smallest one to Al (1− x ) Rh ( x ) (acac) 3 system. The magnitude of the obtained k values was associated with the ability of the guest complexes to scavenge electrons and are closely related to the redox properties of the complexes. X-ray diffraction measurements were made to confirm the hypothesis that all studied samples are single phase systems and that the introduction of the guest molecules in the matrix lattice does not result in significant crystalline changes. These results are well explained in the framework of the spur model and show that the chemical properties determine the Ps yields in molecular solids, regardless of their free volume characteristics.

Preparation and X-Ray Crystal Structure of a Novel Nickel(II) Complex with Dithiocarbimate

The reaction of potassiumN-(methanesulfonyl)-dithiocarbimate, K2[S2C=NSO2CH3], with nickel(II) chloride hexahydrate, NiCl2·6H2O, formed the complex anion bis(N-(methanesulfonyl)-dithiocarbimate)nickelate(II), [Ni(S2C=NSO2CH3)2]2}-, which was isolated as its tetra-n-butylammonium salt. The UV-Vis data obtained were consistent with the formation of a nickelsulfur diamagnetic planar complex. The1H NMR and the13C NMR spectra showed the expected signals for then-Bu4N+ cation and the dithiocarbimate moiety. The single-crystal structure analysis showed that tetra-n-butylammonium bis(N-(methanesulfonyl)-dithiocarbimate)nickelate(II), (Bu4N)2[Ni(S2C=NSO2CH3)2], crystallizes in the monoclinic space groupP2l/c witha=9.3197(5),b=15.0795(8),c=17.5286(9) å,Β=91.262(3)‡,V=2462.8(3) å3, andZ=2. The nickel atom is coordinated to four sulfur atoms.

Crystal Structure, Antibacterial and Cytotoxic Activities of a New Complex of Bismuth(III) with Sulfapyridine

A new complex of Bi(III) and sulfapyridine was synthesized and characterized by elemental analysis, atomic absorption spectrometry, conductivity analysis, electrospray ionization mass spectrometry (ESI-MS), infrared spectroscopy, and single crystal X-ray diffraction methods. The antimicrobial and the cytotoxic activities of the compound were investigated. Elemental and conductivity analyses are in accordance to the formulation [BiCl3(C11H11N3O2S)3]. The structure of the complex reveals a distorted octahedral geometry around the bismuth atom, which is bound to three sulfonamidic nitrogens from sulfapyridine, acting as a monodentate ligand, and to three chloride ions. The presence of the compound in solution was confirmed by ESI-MS studies. The complex is 3 times more potent than the ligand against Salmonella typhimurium, 4 times against Staphylococcus aureus, Shigella dysenteriae, and Shigella sonnei and 8 times more potent against Pseudomonas aeruginosa and Escherichia coli. The compound inhibits the growth of chronic myelogenous leukemia cells with an IC50 value of 44 μM whereas the free ligand has no effect up to 100 μM.

6α,7β‐Dihydroxyvouacapan‐17β‐oic Acid

The title compound, 1,5,5a,6,7,7a,8,9,10,11,11a,11b-dodecahydro-6,7-dihydroxy-8,8,11a- trimethylphenanthro[3,2-b]furan-5-carboxylic acid, C20H28O5, presents both anti-inflammatory and analgesic activities. Two of the six-membered rings adopt chair conformations, whereas the ring fused to furan is in a half-chair conformation. Crystal packing is established by three intermolecular hydrogen bonds.

Manganese-rich natural Franklinite

A natural Franklinite has been characterized by X-ray diffraction techniques. The structure was refined in the space group Fd3m. The almost normal spinel structure was confirmed. All the Zn 2+ ions are located on tetrahedral sites. The best cation distribution was determined to be (Zn 0.65(1) Mn 0.35(1) )[Fe 2 ]O 4 , zinc manganese diiron tetraoxide.

Magnesium aluminium chromite.

The cation distribution in a natural magnesium aluminium chromite spinel (cubic, space group Fd-3m), Al(0.41)Cr(1.42)Fe(0.65)Mg(0.4)O(4), was determined by electron-microprobe analysis, Mossbauer spectroscopy and single-crystal X-ray analysis. Several structural models of the octahedral and tetrahedral cation distributions were tested; the most probable is (Mg(0.40(11))(2+),Al(0.28(5))(3+),Fe(0.39(4))(2+))[Al(0.13(5))(3+),Cr(1.42(6))(3+),Fe(0.26(4))(3+),Phi(0.19)]O(4)(2-), where (...) and [...] represent the tetrahedral and octahedral sites, respectively, and Phi represents a vacancy.