Verónica García-Montalvo

S-adenosyl-L-methionine is able to reverse micronucleus formation induced by sodium arsenite and other cytoskeleton disrupting agents in cultured human cells.

Deficiencies of folic acid and methionine, two of the major components of the methyl metabolism, correlate with an increment of chromosome breaks and micronuclei. It has been proposed that these effects may arise from a decrease of S-adenosyl-L-methionine (SAM), the universal methyl donor. Some xenobiotics, such as arsenic, originate a reduction of SAM levels, and this is believed to alter some methylation processes (e.g. DNA methylation). The aim of the present work was to analyze the effects of exogenous SAM on the micronucleus (MN) frequency induced by sodium arsenite in human lymphocytes treated in vitro and to investigate whether these effects are related to DNA methylation. Results showed a reduction in the MN frequency in cultures treated with sodium arsenite and SAM compared to those treated with arsenite alone. To understand the mechanism by which SAM reduced the number of micronucleated cells, its effect on MN induced by other xenobiotics was also analyzed. Results showed that SAM did not have any effect on the increase in MN frequency caused by alkylating (mitomycin C or cisplatin) or demethylating agents (5-azacytidine, hydralazine, ethionine and procainamide), but it reduced the number of micronucleated cells in those treated with agents that inhibit microtubule polymerization (albendazole sulphoxide and colcemid). Since albendazole sulphoxide and colcemid inhibit microtubule polymerization, we decided to evaluate the effect of SAM on microtubule integrity. Data obtained from these evaluations showed that sodium arsenite, albendazole sulphoxide, and colcemid affect the integrity and organization of microtubules and that these effects are significantly reduced when cultures were treated at the same time with SAM. The data taken all together point out that the positive effects of SAM could be due to its ability to protect microtubules through an unknown mechanism.

A true square-planar tin(II) spiro complex: molecular structure of bis(imidotetraphenyldiselenodiphosphino-Se,Se′)tin(II) and its distorted tetragonal-pyramidal isomer

The yellow complex [Sn{N(SePPh2)2-Se,Se′}2] is the first example of a true square-planar spiro tin(II) compound; the structure of the distorted tetragonal-pyramidal isomer is also described.

Bis(tetraphenylimidothioxodiphosphinate-S,O)lead(II) · benzene, [Pb{SO(PPh2)2N}2] · C6H6: A new asymmetric chelate compound exhibiting dimeric association through intermolecular Pb…S interactions

Abstract The tetraphenylimidodithioxodiphosphinate (SO(PPh 2 ) 2 N) ion forms a stable bis-chelate with Pb II . The crystal and molecular structure of [Pb{SO(PPh 2 ) 2 N} 2 ] · C 6 H 6 was determined by X-ray diffractometry. Units of [Pb{SO(PPh 2 ) 2 N} 2 ] are associated through intermolecular Pb…S interactions, forming a dimer. This complex displays a very distorted ϕ-trigonal bipyramidal structure at the lead atom with a vacant equatorial position, which may be accounted for by the presence of intermolecular lead-sulphur interactions.

Synthesis, spectroscopic characterization and structural studies of dialkyl dithiophosphinate and N,N-dialkyl dithio- and monothio-carbamate derivatives of 1-iodo-1,1,2,3,4,5-hexahydrotellurophene

Abstract The synthesis of the organotellurium(IV) compounds [C4H8TeI(S2PMe2)] (2), [C4H8TeI(S2PEt2)] (3), [C4H8TeI(S2CNC4H6)] (4) and [C4H8TeI(SOCNC5H10)] (6) was achieved. All of them were characterized by IR, 1H-, 13C-, 31P- and 125Te-NMR, mass spectroscopy, elemental analyses and single-crystal X-ray diffraction. In addition, the crystal and molecular structures of the previously known 1,1-diiodotetrahydrotellurophene and [C4H8TeI(S2CNEt2)] (5) were obtained. The geometry around Te(IV) is that of a sawhorse structure in which the lone pair is apparently stereochemically active and occupying an equatorial position in a distorted trigonal bipyramid. All the structures exhibit different supramolecular associations. The intermolecular Te⋯S and Te⋯I interactions result in the formation of dimeric species in 4, and in 1 and 6, respectively. The intermolecular Te⋯S bonds in 2, 3 and 5 lead to formation of one-dimensional polymers.

Lanthanide(III) Complexes with 4,5-Bis(diphenylphosphinoyl)-1,2,3-triazolate and the Use of 1,10-Phenanthroline As Auxiliary Ligand

New lanthanide complexes with 4,5-bis(diphenyl)phosphoranyl-1,2,3-triazolate (L(-)), LnL(3).nH(2)O (1-8) and LnL(3)(phen).nH(2)O (9-16) (Ln = La, Ce, Nd, Sm, Eu, Gd, Tb, Er), have been prepared and spectroscopically characterized. The structures of LnL(3).nH(2)O (Ln = La, Ce, Nd, Sm and Gd) were determined by X-ray crystallography. The metal centers exhibit a distorted trigonal dodecahedron coordination environment with two symmetrically O,O-bidentate ligands and one unsymmetrically O,N- ligand attached to the metal; two oxygen atoms from neighboring dimethyl sulfoxide (DMSO) molecules complete the coordination sphere. This unsymmetrical ligand coordination behavior was also identified in solution through (31)P{(1)H} NMR studies. Photoluminescence spectroscopy experiments in CH(2)Cl(2) for both types of complexes containing Eu(III) (6, 14) and Tb(III) (7, 15) exhibit strong characteristic red and green emission bands for Eu(III) and Tb(III), respectively. Furthermore, NdL(3) (phen).5H (2)O (11) displays emission in the near-infrared spectral region ((4)F(3/2) --> (4)F(9/2) at 872 nm and (4)F(3/2) --> (4)F(11/2) at 1073 nm). The complexes containing 1,10-phenantroline exhibit higher quantum yields upon excitation at 267 nm, indicating that this auxiliary ligand promotes the luminescence of the complexes; however, luminescence lifetimes (tau) in this case are shorter than those of the LnL(3).nH(2)O series.

Synthesis of the First Neutral Spiro Selenium(II) Complex Containing a True Square Planar Se(Se4) Core – Preparation and Crystal Structure of Bis[N‐(diphenylphosphanylselenoyl)‐P,P‐diphenylphosphanylselenoic amidato‐Se, Se′]selenium(II)

The Bis[N-(diphenylphosphanylselenoyl)-P,P-diphenylphosphanylselenoic amidato-Se,Se′]selenium(II) (1) was prepared by treating [K{N(SePPh2)2}] with [Se{S2P(O-iPr)2}2] in THF. The title compound was characterized by means of IR and 31P-NMR spectroscopy and positive-ion FAB mass spectrometry and elemental analysis. The molecular structure was determined using single-crystal X-ray diffraction. The Se(Se4) core exhibited a quasi perfect square planar geometry. Two selenide ligands are coordinated symmetrically to the central atom forming a spiro complex.

Synthesis, characterization and crystal structure of 1,3-dihydro-2λ4-benzotellurole-2,2-diyl bis(N-piperidine-dithiocarbamate), [1,2-C6H4(CH2)2Te(S2CNC5H10)2] (1), 1,3 dihydro-2λ4-benzotellurole-2-iodo-2-yl-diethyldithiophosphinate, [1,2-C6H4(CH2)2TeI(S2PEt2)] (2) and 1,3-dihydro-2λ4-benzotellurole-2-iodo-2-yl dimethyldithiophosphinate, [1,2-C6H4(CH2)2TeI(S2PMe2)] (3)

Abstract Three new 1,1-dithiolato organoyltellurium(IV) compounds were synthesized, [1,2-C6H4(CH2)2Te(S2CNC5H10)2] (1), [1,2-C6H4(CH2)2TeI(S2PEt2)] (2), and [1,2-C6H4(CH2)2TeI(S2PMe2)] (3). They have been characterized by means of IR, 1H, 13C, 31P NMR spectroscopy, positive-ion FAB mass spectrometry, elemental analysis and single-crystal X-ray diffractomery. The 1,1-dithiolato ligands display an anisobidentate chelating coordination mode on interacting with the tellurium centre. Two 1,1-piperidindithiocarbamates are attached to the tellurium atom in 1, while a iodine atom and only one 1,1-dialkyldithiophosphinate are bonded to Te in compounds 2 and 3. The solid state structures show that the compounds 2 and 3 exhibits important intermolecular interactions (Te⋯I(b) for 2 and Te⋯S(b) for 3). These interactions result in the formation of a dimer in 2, and of a one-dimensional polymer in 3. Compound 1 shows weaker intermolecular Te⋯S(b) interactions.

Influence of the steric effect on the conformation of stannocanes. The synthesis and X-ray structure of X(CH2CH2S)2Sn(n-Bu)Cl (X=S, O)

Abstract 5-Chloro-5- n -butyl-1-oxa-4,6-dithia-5-stannocane ( 1 ) and 2-chloro-2- n -butyl-1,3,6-trithia-2-stannocane ( 2 ) have been prepared by reacting n -butyltin trichloride with 2-mercaptoethyl ether and 2-mercaptoethyl sulphide, respectively. Complexes 1 and 2 were characterised by elemental analyses, IR, EI MS, and multinuclear NMR ( 1 H, 13 C, 119 Sn). The molecular structures of 1 and 2 were determined by X-ray analyses. The eight-membered rings in both compounds are in the boat–chair conformation with a 1,5 transannular Sn⋯O (2.409(7) A) or Sn⋯S (2.7855(16) A) interaction. The coordination around the Sn atoms can be described as trigonal bipyramidal with Cl and X in the apical positions.

Synthesis and characterization of thorium and uranium tetraphenylimidophosphinate complexes. Crystal and molecular structures of Th(tpip)4, U(tpip)4 and UCl(tpip)3

Abstract Tetra(tetraphenylimidophosphinato)thorium, Th(tpip)4 (1), was obtained from Th(NO3)4·4H2O and Ktpip in aqueous medium. The analogous uranium compound, U(tpip)4 (2), has been prepared by reacting UCl4 with Ktpip in a 1:4 stoichiometric ratio, either in THF or in aqueous solution. X-ray diffraction analysis showed that compounds 1 and 2 were isostructural. The metal center is eight-coordinate by way of four bidentate tetraphenylimidophosphinate ligands in a square antiprismatic configuration. UCl(tpip)3 (3) has been isolated from the reaction of uranium tetrachloride with 3 equiv. of Ktpip in aqueous solution. When this reaction was run in THF both compounds, U(tpip)4 and UCl(tpip)3, were obtained. The molecular structure of 3 has been determined by X-ray crystallography. The uranium atom is seven-coordinate in a pentagonal bipyramidal configuration. These compounds were also characterized by infrared and 1H and 31P NMR spectroscopies.

Two New Carbon-Free Indium(III) Asymmetric Chelates – Synthesis and X-ray Crystal Structures of [In{Ph2P(O)NP(S)Ph2-O,S}3]·3/4 C6H6 and [InCl{Ph2P(S)NP(Se)Ph2-S,Se}2]

The ligands [Ph2(S)PNHP(X)Ph2]− (X = O, Se) react with InCl3 in a 3:1 ratio to give a tris-chelate [In{Ph2P(O)NP(S)Ph2-O,S}3]·0.75 C6H6 (2) and the unexpected pentacoordinate derivative [InCl{Ph2P(Se)NP(S)Ph2-Se,S}2] (3). These compounds have been characterized by means of IR, 1H- and 31P-NMR spectroscopy, positive-ion FAB mass spectrometry and elemental analysis. The molecular structures have been determined by single-crystal X-ray diffraction analysis. The coordination geometry in 2 resembles that observed in the three analogous tris-chelates incorporating the corresponding symmetrical oxygen, sulfur and selenium ligands. Compound 3 exhibits a very distorted trigonal-bipyramidal geometry at indium, where both the selenium and chlorine atoms are in equatorial positions, while the sulfur atoms are in axial positions.