A new mixed ligand-silver(I) complex of formula [Ag(tpp)(2)(p-Hbza)] (1) (p-HbzaH = 4-hydroxybenzoic acid and tpp = triphenylphosphine) has been synthesized and characterized by elemental analysis, mp, vibrational spectroscopy (mid- and far-FT-IR), (1)H-NMR, UV-vis, ESI-MS spectroscopic techniques and X-ray crystallography. Complex 1 and the already known mixed ligand-silver(I) complexes of formulae [Ag(tpp)(2)(salH)] (2) (salH(2) = salicylic acid or 2-hydroxy-benzoic acid) and {[Ag(tpp)(3)(asp)](dmf)} (3) (aspH = o-acetylsalicylic acid) were used for the clarification of the cytostatic activity mechanism. Thus, 1-3 were tested for their in vitro cytotoxic activity against leiomyosarcoma (LMS) and human breast adenocarcinoma (MCF-7) cells with trypan blue and Thiazolyl Blue Tetrazolium Bromide (MTT) assays. For both cell lines, complexes 1-3 were found to be more active than cisplatin. Due to the morphology of the LMS cells after incubation with 1-3, the type of cell death was evaluated by flow cytometry assay and DNA fragmentation. The results show that LMS cells undergo programmed cell death (apoptosis). DNA binding tests indicate the ability of complexes 1-3 to modify the activity of the cells. The binding constants of 1-3 towards calf-thymus DNA (CT-DNA) ((27.7 ± 7.9) × 10(4) (1), (13.3 ± 6.5) × 10(4) (2) and (11 ± 2.8) × 10(4) (3) M(-1)) indicate strong interaction. Moreover, the influence of complexes 1-3 on the catalytic peroxidation of linoleic acid to hydroperoxylinoleic acid by the enzyme lipoxygenase (LOX) was kinetically studied. Finally, docking studies on DNA binding interactions were performed.

The crystal structure of a Z-DNA hexamer duplex d(CGCGCG)2 determined at ultra high resolution of 0.55 Å and refined without restraints, displays a high degree of regularity and rigidity in its stereochemistry, in contrast to the more flexible B-DNA duplexes. The estimations of standard uncertainties of all individually refined parameters, obtained by full-matrix least-squares optimization, are comparable with values that are typical for small-molecule crystallography. The Z-DNA model generated with ultra high-resolution diffraction data can be used to revise the stereochemical restraints applied in lower resolution refinements. Detailed comparisons of the stereochemical library values with the present accurate Z-DNA parameters, shows in general a good agreement, but also reveals significant discrepancies in the description of guanine-sugar valence angles and in the geometry of the phosphate groups.

Direct reaction of thiazolidine‐2‐thione (tzdtH), an anti‐thyroidal agent with diiodine in a molar ratio of 1:2 caused the heterolytic cleavage of diiodine and formation of [{(tzdtH)2I+}·I3−·2I2] (1), whereas the reaction of benzothiazole‐2‐thione (bztzdtH) with diiodine in a molar ratio of 1:2 and 1:1 resulted in the formation of the [{(bztzdtH)I2}·I2] (2) and [(bztzdtH)I2] (3) charge‐transfer (c.t.) complexes. In addition, the reaction between benzimidazole‐2‐thione (bzimtH) with diiodine in a molar ratio 1:2 yielded the c.t. complex [{(bzimtH)I2}2·I2·2H2O] (4). All reactions were carried out in dichloromethane. The molecules have been characterized by m.p., elemental analyses, and FT‐Raman, FT‐IR, UV/Vis and 1H NMR spectroscopy. Crystal structures of the named complexes have been determined by X‐ray diffraction at −103 °C (1), 20 °C (2 and 3) and −168 °C (4). The charge‐transfer nature of the bonds of the adducts (1−4) has been verified by the lengthening of the I−I bond lengths as compared to the S−I bond lengths, by the characteristic c.t. bands observed in the UV spectra and by the shifts of frequencies measured for the I−I bond vibration in the FT‐Raman spectra of the complexes. Compound 1 (C3H5NS2I4) is monoclinic with a space group P21/n and a = 9.145(2) Å, b = 13.259(2) Å, c = 10.615(2) Å, β = 106.30(2)°, Z = 4. The complex is ionic, containing an S−I+−S linkage and an I3− counter anion. Compound 2 [C7H5NS2I4, monoclinic, space group P21/n, a = 8.357(2) Å, b = 17.829(4) Å, c = 9.603(2) Å, Z = 4, β = 94.39(3)°] consists of a benzothiazole‐2‐thione ligand bonded with an iodine atom through a sulfur atom. A neutral diiodine molecule is also co‐crystallized. A benzothiazole‐2‐thione ligand is also bonded through its sulfur atom to an iodine atom in molecule 3 [C7H5NS2I2, orthorhombic, space group P212121, a = 4.189(1) Å, b = 9.770(3) Å, c = 27.704(8) Å, Z = 4]. Extended intramolecular N−H···I contacts link the molecules forming a supramolecular assembly. The crystal structure of 4 (C7H6N2SI3·H2O) reveals a monoclinic space group P21/c and a = 13.4828(14) Å, b = 4.6704(4) Å, c = 21.267(2) Å, β = 101.029(8)°, Z = 4. It consists of a benzimidazole‐2‐thione ligand bonded to an iodine atom through a sulfur atom. An extended intramolecular linkage via I(2)···H(4)[C(4)] leads to the formation of dimers, while an extended hydrogen‐bonding network {H(12w)[O(12)w]···N(3), O(1w)···N(3)} links the alternate parallel dimers forming a supramolecular assembly. Attempts to draw conclusions on the behavior of a thione, when used as an anti‐thyroidal agent, towards diiodine have been made. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

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Five new antimony(III) complexes with the heterocyclic thiones 2-mercapto-benzimidazole (MBZIM), 5-ethoxy-2-mercapto-benzimidazole (EtMBZIM), and 2-mercapto-thiazolidine (MTZD) of formulas {[SbCl(2)(MBZIM)4]+.Cl-.2H(2)O. (CH(3)OH)} (1), {[SbCl(2)(MBZIM)4]+.Cl-.3H(2)O.(CH3CN)} (2), [SbCl(3)(MBZIM)2] (3), [SbCl(3)(EtMBZIM)(2)] (4), and [SbCl(3)(MTZD)2] (5) have been synthesized and characterized by elemental analysis, FT-IR, far-FT-IR, differential thermal analysis-thermogravimetry, X-ray diffraction, and conductivity measurements. Complex {[SbCl2(tHPMT)(2)]+Cl-}, (tHPMT = 2-mercapto-3,4,5,6-tetrahydro-pyrimidine), already known, was also prepared, and its X-ray crystal structure was solved. It is shown that the complex is better described as {[SbCl3(tHPMT)(2)]} (6). Crystal structures of all other complexes (1-5) have also been determined by X-ray diffraction at ambient conditions. The crystal structure of the hydrated ligand, EtMBZIM.H2O is also reported. Compound [C(28)H(24)Cl(2)N(8)S(4)Sb.2H(2)O.Cl.(CH(3)OH)] (1) crystallizes in space group P2(1), with a = 7.7398(8) A, b = 16.724(3) A, c = 13.717(2) A, beta = 98.632(11) degrees, and Z = 2. Complex [C(28)H(24)Cl(2)N(8)S(4)S(b).Cl.3H(2)O.(CH(3)CN)] (2) corresponds to space group P2(1), with a = 7.8216(8) A, b = 16.7426(17) A, c = 13.9375(16) A, beta = 99.218(10) degrees , and Z = 2. In both 1 and 2 complexes, four sulfur atoms from thione ligands and two chloride ions form an octahedral (Oh) cationic [SbS(4)Cl(2)]+ complex ion, where chlorides lie at axial positions. A third chloride counteranion neutralizes it. Complexes 1 and 2 are the first examples of antimony(III) compounds with positively charged Oh geometries. Compound [C(14)H(12)Cl(3)N(4)S(2)S(b)] (3) crystallizes in space group P, with a = 7.3034(5) A, b = 11.2277(7) A, c = 12.0172(8) A, alpha = 76.772(5) degrees, beta = 77.101(6) degrees, gamma = 87.450(5) degrees, and Z = 2. Complex [C(18)H(20)Cl(3)N(4)O(2)S(2)S(b)] (4) crystallizes in space group P1, with a = 8.6682(6) A, b = 10.6005(7) A, c = 13.0177(9) A, alpha = 84.181(6) degrees, beta = 79.358(6) degrees, gamma = 84.882(6) degrees, and Z = 2, while complex [C(6)H(10)Cl(3)N(2)S(4)S(b)] (5) in space group P2(1)/c shows a = 8.3659(10) A, b = 14.8323(19) A, c = 12.0218(13) A, beta = 99.660(12) degrees, and Z = 4 and complex [C(8)H(16)Cl(3)N(4)S(2)S(b)] (6) in space group P1 shows a = 7.4975(6) A, b = 10.3220(7) A, c = 12.1094(11) A, alpha = 71.411(7) degrees, beta = 84.244(7) degrees, gamma = 73.588(6) degrees, and Z = 2. Crystals of complexes 3-6 grown from acetonitrile solutions adopt a square-pyramidal (SP) geometry, with two sulfur atoms from thione ligands and three chloride anions around Sb(III). The equatorial plane is formed by two sulfur and two chloride atoms in complexes 3-5, in a cis-S, cis-Cl arrangement in 3 and 5 and a trans-S, trans-Cl arrangement in 4. Finally, in the case of 6, the equatorial plane is formed by three chloride ions and one sulfur from the thione ligand while the second sulfur atom takes an axial position leading to a ...

The electron density of 1-phenyl-4-nitroimidazole was analyzed by X-ray diffraction at 0.55 Å resolution. The topology of the bonding scheme within the molecule as well as of the weak intermolecular C−H···O and C−H···N hydrogen bonds has been investigated. The topological analysis and the deformation density peak heights on the covalent bonds of the imidazole ring are consistent with the usual chemical knowledge. The nitro group has an electron-withdrawing effect, as it is globally negatively charged and the electrostatic potential around it is slightly negative. This potential is significantly weaker than that generated by other oxygen-containing chemical entities, which is related to the hydrophobicity of the nitro group. The nitro group forms three weak C−H···O hydrogen bonds, and the unsubstituted imidazole nitrogen is also hydrogen-bonded to a C−H group, as confirmed by the presence of critical points in the topological analysis.

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Functionalization of octavinylsilsesquioxane (Vi(8)T(8), 1) by two reactions catalyzed by ruthenium complexes is reported: a silylative coupling reaction catalyzed by [RuHCl(CO)(PCy(3))(2)] (I) and cross-metathesis catalyzed by first- (II) and second-generation (III) Grubbs' catalysts. The two reactions of 1 with styrene take place highly regio- and stereoselectively (the X-ray structure of the product 2 has also been obtained); the cross-metathesis of 1-hexene and allyltrimethylsilane occurs quite effectively, whereas the silylative coupling with these compounds gives a mixture of isomers. Functionalization of 1 with heteroatom-substituted vinyl derivatives (Si, O, N) by silylative coupling reaction has been found to be highly efficient, but cross-metathesis appears to be the more effective method for the synthesis of S-substituted vinyl-silsesquioxane.