Eleonora Freire

Mercury(II) halide complexes with N-donor organic ligands: crystal and molecular structure of HgI2R, R = 1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline, bipyridine

AbstractThe synthesis, characterization and single crystal X-ray structure of three compounds of general formula HgI2R (R = phen[1], dmph [2] and bpy[3]) are presented. The crystal data for the three compounds are: [1], triclinic, space group P

X-Ray Study of Two Novel Nickel(II)–Thiosulfate Compounds

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X-ray diffraction and Raman spectroscopy study of white decorations on tricolored ceramics from Northwestern Argentina.

(#2) a = 7.902(2), b = 9.479(2), c = 10.002(2) Å, α = 91.45(2), β = 111.34(2), γ = 100.82(2)° [2]: monoclinic, space group C2/c (#15) a = 15.670(3), b = 11.640(2), c = 9.730(2) Å, β = 114.57(3)° [3]: triclinic, space group P1¯ (#2) a = 9.472(1), b = 9.507(1), c = 9.023(1) Å, α = 98.46(1), β = 102.89(1), γ = 119.62(1)°. Compounds [1] and [2] are monomers, with highly distorted tetrahedral environments around Hg. In [3], instead, there is a significant intermolecular I···Hg interaction leading to the formation of softly bound dimers linking two pentacoordinated cations. The structure is compared with related ones in the literature.

X-Ray Study of Two ZnII and CdII 2,2'-Dipyridylamine Thiosulfate Compounds

Alzheimers disease (AD) is a neurodegenerative disorder associated with memory impairment and cognitive deficit. Most of the drugs currently available for the treatment of AD are acetylcholinesterase (AChE) inhibitors. In a preliminary study, significant AChE inhibition was observed for the ethanolic extract of Grindelia ventanensis (IC₅₀=0.79 mg/mL). This result prompted us to isolate the active constituent, a normal labdane diterpenoid identified as 17-hydroxycativic acid (1), through a bioassay guided fractionation. Taking into account that 1 showed moderate inhibition of AChE (IC₅₀=21.1 μM), selectivity over butyrylcholinesterase (BChE) (IC₅₀=171.1 μM) and that it was easily obtained from the plant extract in a very good yield (0.15% w/w), we decided to prepare semisynthetic derivatives of this natural diterpenoid through simple structural modifications. A set of twenty new cativic acid derivatives (3-6) was prepared from 1 through transformations on the carboxylic group at C-15, introducing a C2-C6 linker and a tertiary amine group. They were tested for their inhibitory activity against AChE and BChE and some structure-activity relationships were outlined. The most active derivative was compound 3c, with an IC₅₀ value of 3.2 μM for AChE. Enzyme kinetic studies and docking modeling revealed that this inhibitor targeted both the catalytic active site and the peripheral anionic site of this enzyme. Furthermore, 3c showed significant inhibition of AChE activity in SH-SY5Y human neuroblastoma cells, and was non-cytotoxic.

Two hydrates of 2,6-bis­(1H-benzimidazol-2-yl)­pyridine

Two novel nickel thiosulfate complexes have been prepared and their crystal structures determined: NiS2O3(dmph)(H2O)·H2O·CH3OH (1) (dmph = 2,9-dimethyl-1,10-phenanthroline), which to our knowledge is the first pentacoordinated nickel thiosulfate complex described so far, and NiS2O3(dmph) (2), a hexacoordinated complex which displays a thiosulfate binding mode with no precedents in the literature, viz. bridging solely through oxygen. Compound (1) is monoclinic, C2/c, a 26.269(5), b 7.641(3), c 18.381(3) A, β 97.00(2)˚, V 3662(2) A 3 ,Z 8, conventional R (on F) being 0.049 for 2217 No observed reflections (I > 2σ(I)). Compound (2) is also monoclinic, P21/n, a 11.108(2), b 10.955(2), c 11.666(2) A, β 103.32(3)˚, V 1381.4(5) A 3 , Z 4, R 0.036, No 2497.

A polymorphic form of 4,4‐dimethyl‐8‐methylene‐3‐azabicyclo[3.3.1]non‐2‐en‐2‐yl 3‐indolyl ketone, an indole alkaloid extracted from Aristotelia chilensis (maqui)

The crystal and molecular structure of two novel nickel complexes stabilized by pentathionate counterions, namely acetato(O,O′)diaqua biquinoline(N,N′)nickel(II) hemipentathionate dihydrate (1) and diterpyridine (N,N′,N″)-nickel(II) pentathionate tetrahydrate (2), are presented. Compound (1) is monoclinic, C2/c, a 21.5628(4), b 11.3354(2), c 20.2873(4) A, β 92.433(1)˚, V 4954.2(2) A3, Z 8, conventional R (on F) being 0.042 for 3444 No observed reflections (I > 2σ(I)). Compound (2) is triclinic, P1–, a 12.461(1), b 12.781(1), c 23.542(2) A, α 80.246(5), β 79.714(5), γ 88.680(6)˚, V 3635.9(6) A3, Z 4, R 0.062, No 6255. In both compounds the pentathionate anions act as counterions of the octahedral complex cations and have been formed in situ through reactions involving the thiosulfate group present in the synthesis process. Manuscript received: 4 January 2001.

EMPLEO DE ESPECTROSCOPIA RAMAN, DIFRACCIÓN DE RAYOS X Y MICROSCOPIA ELECTRÓNICA PARA EL ANÁLISIS DE PIGMENTOS EN CERÁMICAS VAQUERÍAS

White virgules, commas, and dot designs on tricolored ceramics are sporadically found in different archaeological sites located in Northwestern Argentina area, as Puna and Quebrada de Humahuaca. This decorating style has been reported in several articles, but few previous archaeometric studies have been carried out on the pigment composition. Fragments from Puna and Quebrada archaeological sites, belonging to Regional Development Period (900-1430 AD), were analyzed by X-ray diffraction and Raman spectroscopy in order to characterize the pigments employed. Red and black pigments are based on iron and manganese oxides, as it has been extensively reported for the NW Argentina area. White pigments from white virgules, comma, and dot designs have shown different composition. Hydroxyapatite was found in samples from Doncellas site (North Puna region), and calcium and calcium-magnesium containing compounds, as vaterite and dolomite, along with titanium containing compounds were detected on samples from Abralaite (Central Puna region) and Gasoducto (Quebrada de Humahuaca region). It has been concluded that pigment composition is not characteristic of a unique region.

Aripiprazole salts. I. Aripiprazole nitrate.

Two ZnII and CdII thiosulfato(2,2′-dipyridylamine) complexes, namely [Zn2(S2O3)2(dpa)3·H2O]·H2O (1) and [Cd(S2O3)(dpa)(H2O)] (2) (dpa = 2,2′-dipyridylamine), have been prepared and their crystal structures determined and compared with related structures in the literature. Compound (1) is triclinic P1–, a 10.170(3), b 12.821(3), c 14.899(3) A, α 108.33(2), β 90.34(2), γ 109.02(2)˚, V 1730.7(7) A3, Z 2, conventional R (on F) being 0.031 for 6379 No observed reflections (I >2σ (I)). Compound (2) is monoclinic, P21/c, a 9.897(3), b 19.235(4), c 7.205(1) A, l 101.48(7)˚, V 1344.2(4) A3, Z 4, R 0.032, No 2494.