Charlane C. Corrêa

Novel antitumor adamantane–azole gold(I) complexes as potential inhibitors of thioredoxin reductase

AbstractGold complexes that could act as antitumor agents have attracted great attention. Heterocyclic compounds and their metal complexes display a broad spectrum of pharmacological properties. The present study reports the preparation and characterization of four novel gold(I) complexes containing tertiary phosphine and new ligands 5-adamantyl-1,3-thiazolidine-2-thione, 3-methyladamantane–1,3,4-oxadiazole-2-thione. Spectroscopic data suggest that gold is coordinated to the exocyclic sulfur atom in all cases, as confirmed by X-ray crystallographic data obtained for complex (1) and supported by quantum–mechanical calculations. The cytotoxicity of the compounds has been evaluated in comparison to cisplatin and auranofin in three different tumor cell lines, colon cancer (CT26WT), metastatic skin melanoma (B16F10), mammary adenocarcinoma (4T1) and kidney normal cell (BHK-21). The gold complexes were more active than their respective free ligands and able to inhibit the thioredoxin reductase (TrxR) enzyme, even in the presence of albumin. Molecular modeling studies were carried out to understand the interaction between the compounds and the TrxR enzyme, considered as a potential target for new compounds in cancer treatment. The docking results show that the adamantane ring is essential to stabilize the ligand–enzyme complex prior the formation of covalent bond with gold center.Graphical abstractThe structure of the new gold compounds was established on the basis of spectroscopic data, DFT calculations and X-ray diffraction. TrxR inhibition was evaluated and the results correlated with the assays in tumor cells, suggesting the TrxR as possible target for these compounds.

2-D coordination polymers of copper and cobalt with 3,4-pyridinedicarboxylic acid: synthesis, characterization, and crystal structures

Two new complexes involving 3,4-pyridinedicarboxylic acid (3,4-H2pdc), copper(II) and cobalt(II) complexes, {[Cu(3,4-Hpdc)2(H2O)2]·2dmso}n (1) and {[Co(3,4-Hpdc)2(H2O)2]·2H2O·2dmso}n (2) (dmso = dimethylsulfoxide), have been synthesized by the diffusion method and characterized by elemental analysis, IR spectroscopy, thermal analysis, powder and single-crystal X-ray diffraction analysis, and electron paramagnetic resonance (EPR). In both compounds, the metal coordination sphere is composed of a trans-MO4N2 core and adopts a distorted octahedral geometry in accordance with X-ray diffraction and EPR results. 3,4-Hpdc− ligands bridge the metal centers giving two-dimensional (2-D) coordination polymers with four-connected uninodal nets of (4,4) topology. Graphical Abstract

Catalyst free decarboxylative trichloromethylation of aldimines

A catalyst free decarboxylative trichloromethylation of imines to afford different trichloromethyl sulfonyl and sulfinyl amines has been presented. Only DMSO as a solvent at room temperature was necessary to provide the corresponding products in good to high isolated yields. A highly diastereoselective version was carried out, leading to the sulfinylimine with good yield and near perfect diastereoselectivity. Regarding the reaction profile, ATR-FTIR spectroscopy was employed to support the entire mechanism and also to provide details on the trichloroacetate salts behavior against electrophiles and in the presence of different solvents.

cis-Dichloridobis-(5,5'-dimethyl-2,2'-bipyridine)-manganese(II) 2.5-hydrate.

The metal site in the title compound [MnCl2(C12H12N2)2]·2.5H2O has a distorted octahedral geometry, coordinated by four N atoms of two 5,5′-dimethyl-2,2′-dipyridine ligands and two Cl atoms. Two and a half water molecules of hydration per complex unit are observed in the crystal structure. The compounds extend along the c axis with O—H⋯Cl, O—H⋯O, C—H⋯Cl and C—H⋯O hydrogen bonds and π–π interactions [centroid-centroid distance = 3.70 (2) Å] contributing substantially to the crystal packing. The Mn and one of the water O atoms, the latter being half-occupied, are located on special positions, in this case a rotation axis of order 2.

Preparation and topological properties of two structures with p-sulfobenzoic ligands and Zn2+ and Mn2+ ions

There has been recent interest in coordinated polymers due to their structural and topological properties; therefore, the search for efficient synthesis processes to construct these materials by exploiting different organic ligands has intensified. In this context, two coordinated polymers (Zn–psb and Mn–psb) consisting of p-sulfobenzoic acid and either Zn2+ or Mn2+ ions, respectively, were synthesized by crystallization in gel using ethambutol hydrochloride as a new crystallization agent. Both compounds crystallized in the triclinic system and space group P and have similar unit cell volumes with a difference of 2%. The crystal data for Zn–psb: a = 8.080(4) A, b = 11.385(6) A, c = 12.282(6) A, α = 97.402(4)°, β = 106.530(4)°, and γ = 110.445(5)°; and for Mn–psb: a = 8.055(5) A, b = 10.152(7) A, c = 12.541(8) A, α = 99.084(6)°, β = 95.358(5)°, and γ = 106.090(6)°. Despite the structural similarity, two different networks (tfz-d and pcu for Zn–psb and Mn–psb, respectively) were formed, and their topological properties were explored by reticular chemistry.

Study of the supramolecular interactions of carboxylic acids used as versatile ligands in coordination chemistry

Carboxylate ligands are very versatile because they can adopt different coordination modes towards metal cations, such as monodentate, bidentate-chelate, bidentate bridging and monoatomic bridging. Because of this versatility, these ligands have been widely used in coordination chemistry. In this study the three dimensional structure of the crystal arrangement of 2,5-thiophenedicarboxylic (H2TPD), trans-3-(3- pyridyl)acrylic (HPYA), and 4,4′-sulfonyldibenzoic (H2SFD) acids are determined in order to investigate their supramolecular properties for coordination polymers and metal-organic framework (MOF) constructions.

The zwitterionic structure of 2-hydroxy-4-[(2-hydroxybenzylidene)amino]benzoic acid

The title compound, C₁₄H₁₁NO₄, exists in the solid phase in the zwitterionic form, 2-{[(4-carboxy-3-hydroxyphenyl)iminiumyl]methyl}phenolate, with the H atom from the phenol group on the 2-hydroxybenzylidene ring transferred to the imine N atom, resulting in a strong intramolecular N-H∙∙∙O hydrogen bond between the iminium H atom and the phenolate O atom, forming a six-membered hydrogen-bonded ring. In addition, there is an intramolecular O-H∙∙∙O hydrogen bond between the carboxylic acid group and the adjacent hydroxy group of the other ring, and an intermolecular C-H∙∙∙O contact involving the phenol group and the C-H group adjacent to the imine bond, connecting the molecules into a two-dimensional network in the (103) plane. π-π stacking interactions result in a three-dimensional network. This study is important because it provides crystallographic evidence, supported by IR data, for the iminium zwitterionic form of Schiff bases.

Biosynthesis of silver nanoparticles using Caesalpinia ferrea (Tul.) Martius extract: physicochemical characterization, antifungal activity and cytotoxicity

Background Green synthesis is an ecological technique for the production of well characterized metallic nanoparticles using plants. This study investigated the synthesis of silver nanoparticles (AgNPs) using a Caesalpinia ferrea seed extract as a reducing agent. Methods The formation of AgNPs was identified by instrumental analysis, including ultraviolet–visible (UV–Vis) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) of the AgNPs, and surface-enhanced Raman scattering (SERS) spectra of rhodamine-6G (R6G). We studied the physicochemical characterization of AgNPs, evaluated them as an antifungal agent against Candida albicans, Candida kruzei, Candida glabrata and Candida guilliermondii, and estimated their minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values. Lastly, this study evaluated the cytotoxicity of the AgNPs in murine L929 fibroblasts cells using an MTT assay. Results The UV–Vis spectroscopy, SERS, SEM and XRD results confirmed the rapid formation of spheroidal 30–50 nm AgNPs. The MIC and MFC values indicated the antifungal potential of AgNPs against most of the fungi studied and high cell viability in murine L929 fibroblasts. In addition, this study demonstrated that C. ferrea seed extracts may be used for the green synthesis of AgNPs at room temperature for the treatment of candidiasis.

Desconstruction of Two compounds of p-sulfobenzoic ligand by Reticular Chemistry

The p-sulfobenzoic (4-psb) acid may be used as precursors for different Metal Organic frameworks (MOFs) since they can display different coordination site on the metal with two different functional groups (carboxylate and sulfonate). Details of the crystal packing can be studied using the Reticular Chemistry like a power tool for the deconstruction process of crystal structure of this compounds formed [1]. Two crystal structures Zn-psb and Mn-psb with 4-psb ligand and Zn+2 and Mn+2 ions, respectively, were synthesized. Single crystal-data were collected using an Oxford GEMINI A-Ultra diffractometer with MoKα radiation (λ = 0.71073 Å) at room temperature (298 K). These structures were refined by SHELXL-97 program [2]. Both compounds crystallized in the triclinic system and space group P-1. Zn-psb structure shows a coordinated Zn atom with a slightly distorted octahedral geometry formed by four oxygen atoms from water molecules with averaged distances at 2.08 (2) Å and two oxygen atoms with distances at 2.12 (2) Å derived from the ligand. Mn-psb structure has coordinated Mn atom with a slightly distorted octahedral geometry formed by four oxygen atoms from sulfonate group coordinated with averaged distances at 2.19 (3) Å and two oxygen atoms from water molecules with distances at 2.17 (2) Å. Despite the structural similarities of the structures, a simple modification of the metal in the reaction leads to a tendency for different network. Thus, Zn-psb structure consists of a network-connected system binodal (3,8). This network is deposited in Reticular Chemistry Structural Resource as a network type tfz-d system with tilling of transitivity [2222] and signature 3[4^2.6^2] + 2[6^3]. However, the Mn-psb structure leads to formation of a regular network with pcu topologic type presenting tilling with transitivity [1111] and signature [4^6]. The system of cavities formed into networks are blocked by ligands in the crystal structure.

Ethyl 2-[(carbamoyl­amino)­imino]­propano­ate hemihydrate

The title compound, C6H11N3O3·0.5H2O, has two independent molecules and one molecule of water in the asymmetric unit. The crystal packing is stabilized by intermolecular N—H⋯N, O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds. These interactions form a two-dimensional array in the ab plane with a zigzag motif which has an angle close to 35° between the zigzag planes. The hydrogen bonding can be best described using the graph-set notation as N 1 = C(10)R 2 2(10)R 2 2(8) and N 2 = R 6 4(20)R 2 2(8).