Síntesis y caraterización del ligando tris-(2-tiosalicilamidoetil)amina y sus complejos de hierro e indio

The coordination chemistry of the hexadentate ligand, tris(2-thiosalicylamidoethyl)amine, (LH3), was studied. The reaction of the ligand trianion with iron(III) and indium(III) yields monomeric hexacoordinate complexes, LFe·HCl and LIn. The complexes were characterized by spectroscopic, magnetic and electrochemical methods.  

Effect of pretreatment temperature on the surface modification of diatomite with trimethylchlorosilane

Artículo científicoDiatomite samples from Costa Rica were purified using acidic treatments with hydrochloric acid, thermally treated (400–1000 C) and then silylated with trimethylchlorosilane in toluene under inert atmosphere. The purification process allows to decrease the concentration of metals presented in the crude diatomite, as is confirmed by X-ray Fluorescence (XRF) Analysis. The silylated materials were analyzed by using Hyperpolarized 129Xe Nuclear Magnetic Resonance Spectroscopy (HP 129Xe NMR), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), rehydration tests, and contact angle measurements. XRD measurements indicate that diatomite is mainly amorphous, but presents several crystalline phases (kaolinite, cristobalite, and quartz). Pretreatments at high temperatures cause changes in those crystalline phases, resulting in more amorphous materials. However, there is no difference in the overall structure of purified and thermally treated diatomite samples with respect to the silylation products. In addition, SEM measurements show no effect over the pore structure of the materials. On the other hand, TGA measurements and rehydration tests show lower losses of water for silylated materials prepared using higher pretreatment temperatures. Moreover, HP 129Xe NMR, FTIR, and contact angle measurements evidence a modification due to covalent attachment of Si(CH3)3-groups to the surface, which increases for higher pretreatment temperatures. The results provide valuable information about external factors that influence the surface modification of diatomite. This can be useful to control modifications that can be achieved in a similar way

Polymers of unidimentional coordination [M(sac)2(H2O)(pyz)]n, (M= Ni2+, Cu2+ and Zn2+, sac =saccharinate, pyz= pyrazine), spectroscopy and magnetic properties

Coordination polymers have been prepared by the hydrothermal reaction of M2+saccharinates (M = Ni, Cu and Zn) and pyrazine, pyz, in a ratio 1:1. The complexes of formula [M(sac)2(H2O)2pyz]n, M = Ni2+ and Zn2+ and [Cu(sac)2(H2O)pyz]n were characterized by spectroscopic methods and elemental analysis, magnetic measurements, single and powder x-ray diffraction. The compounds crystallize in the triclinic space group p-1. The zinc ion is octahedrally coordinated by two sac ions, two water and two pyrazine molecules. The copper ion is penta-coordinated in a distorted square pyramidal geometry with the pyrazine molecules in the axial position. The metal atoms are connected via pyrazine μ-N,N’-coordination and form linear chains, containing a network of hydrogen bonds between the chains, that build a 2D sheet structure

Synthesis, characterization and redox behaviour of mixed ligand copper(II) saccharinate complexes

Three mixed-­ligand complexes of Cu(II) with saccharin (sac), pyrazole, (Hpz), imidazole, (Himid) were synthesized and characterized on the basis of elemental analysis, FT-­IR spectroscopy, magnetic susceptibility, EPR spectra, and X-­ray diffraction. The reaction of [Cu(sac)2(H2O)4] ⋅ 2H2O with pyrazol in methanol resulted in a mononuclear pentacoordinated compound [Cu(sac)2(Hpz)3] (1) and a trinuclear N,N.bridged compound [Cu3(sac)2(Hpz)3(pz)3)2(OH)] (2), forming a nine membered [-Cu-­N-­N-­]3 ring and μμ3-­‐‐OH bridge; each Cu(II) ion is tetracoordinated, with weak axial interactions from saccharinate ions.The Himidazole compound [Cu2(sac)4(Himid)4] (3) has a dinuclear structure with two saccharinate ions as bridge; each Cu(II) ions has a penta-­coordination sphere, two N-­coordinated and one O-­coordinated saccharinate ions on the equatorial plane, and two imidazole molecules in the axial positions.Se sintetizaron tres complejos de cobre(II) con una mezcla de ligandos, sacarina (sac) y pirazol (Hpz) e imidazole (Himid). Los complejos se caracterizaron por análisis elemental, espectroscopía IR-­FT, susceptibilidad magnética, esoectroscopia EPR y difracción de rayos X. La reacción de [Cu(sac)2(H2O)4] ⋅ 2H2O con pirazol en methanol produce un compuesto mononuclear pentacoordinado, [Cu(sac)2(Hpz)3] (1) y uno trinuclear [Cu3(sac)2(Hpz)3(pz)3)2(OH)] (2), con puentes N,N, que forman un anillo de nueve miembros [-­Cu-­N-­N-­]3 y un puente μμ3-­‐‐OH; cada átomo de cobre está tetracoordinado con una leve interacción axial de los iones sacarinato. El compuesto con imidazol [Cu2(sac)4(Himid)4] (3) posee una estructura dinuclear con dos iones sacarinato puente, cada átomo de cobre está pentacoordinado, con dos iones sacarinatos unidos por el átomo de nitrógeno y uno unido por un átomo de oxígeno en el plano equatorial y dos moléculas de imidazol en la posición axial

Biochemical characterization of extracellular polymeric substances from endodontic biofilms.

Apical periodontitis is frequently associated with the presence of bacteria biofilm, which has an indisputable impact on the prognosis of endodontic therapy due to the high resistance to adverse environmental conditions, chemicals, and antibiotic therapy that characterize bacteria within biofilm. The biofilm matrix acts as a protective shield over the encased microorganisms. The aim of this investigation was to identify the main biochemical components of biofilm matrix from endodontic mono- and dual-species biofilms. Enterococcus faecalis and Actinomyces naeslundii were cultured as mono- and dual-species biofilms for 14 days. Crude extracellular polymeric substances (EPSs) from biofilm matrices were extracted using chemical and physical methods. High-performance liquid chromatography, gas chromatography, and mass spectrometry were used to determine the carbohydrate, protein, and fatty acid components. Chemical analysis of the biofilm matrices revealed that they were mainly composed of stachyose, maltose, and mannose carbohydrates. The protein profile in all biofilm samples showed abundant oxidoreductases and chaperone proteins and some virulence- associated proteins mainly located in the membrane surface. High percentages of saturated and monounsaturated fatty acids were identified in all biofilm matrices, with a major prevalence of palmitic, stearic, and oleic acids. Based on the results, it was possible to obtain for the first time a general overview of the biochemical profile of endodontic biofilm matrices

Raman Spectroscopic Characterization of Endodontic Biofilm Matrices

Endodontic persistent infections are often mediated by bacterial biofilms. This mode of bacterial growth is characterized by the presence of a matrix mainly composed of extracellular polymeric substances (EPSs) that protect the encased microorganisms. To establish better control and disinfection protocols, elucidation of the main components of biofilm matrices present in endodontic infections is required. The aim of the present study was to characterize the principal components of E. faecalis, A. naeslundii, and dual-species biofilm matrices by means of Raman spectroscopy and confocal scanning laser microscopy (CSLM) techniques. The total biomass of biofilms was quantified via crystal violet assays, and the monospecies biofilms showed higher biomass than the dual-species biofilms. Raman spectroscopy and confocal laser scanning microscopy were used to identify the biochemical composition and structure of the biofilm matrices. Spectra originating from the biofilms of two endodontic pathogens show the presence of carbohydrates, proteins, fatty acids, and nucleic acids in all samples; however, variation in the levels of expression of these biomolecules allows spectroscopic differentiation of the biofilms using principal component analysis. This study is the first attempt to identify the composition of monospecies and dual-species biofilms of endodontic origin. Our data provides an important approach to the understanding of molecular dynamics of endodontic infections

Synthesis, structure and spectroscopic characterization of Ni(II), Co(II), Cu(II) and Zn(II) complexes with saccharinate and pyrazole

Four mononuclear mixed-ligand complexes of Co(II), Ni(II), Cu(II) and Zn(II), with saccharin (sac) and pyrazole (Hpz) were synthesized and characterized on the basis of elemental analysis, FT-IR spectroscopy, magnetic susceptibility, thermal analysis data and X-ray diffraction. The [Co(sac)2(Hpz)2(H2O)2] (1) and [Ni(sac)2(Hpz)2(H2O)2] (2) had similar molecular structures but distinct monoclinic crystal structure types (space group P21/n for 1 and P21/c for 2); the members of each pair of ligands were mutually trans. The saccharinate ligands were N-coordinated. The copper complex showed the same coordination environment as the Co and Ni complexes but crystallizes in the triclinic space group P1 and presented pseudo-Jahn–Teller distortion along the O(w)–Cu–O(w) bonds. The [Zn(sac)2(pz)2] complex was tetrahedrally coordinated and crystallized in the monoclinic space group C2/c. Thermal decomposition of the complexes in a nitrogen atmosphere resulted in removal of the water molecules and pyrazole ligands at relatively low temperature and formation of stable metal saccharinates as intermediates, which also decomposed at higher temperatures, about 300 C. 2007 Elsevier Ltd. All rights reserved.Universidad de Costa Rica/[115-98-375]/UCR/Costa RicaMinistery of Science and Technology/[BQU2002-00554]//EspañaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Químic

Antibacterial Efficacy of a Dispersion of Silver Nanoparticles in Citrate Medium for the Treatment of E. faecalis: an In Vitro Study

The purpose of this study was to measure the antibacterial efficacy of a dispersion of silver nanoparticles (AgNP) in a citrate medium tested in two E. faecalis strains. AgNP were synthesized, and AgNP citrate medium (AgNP-CM) dispersion was prepared at a concentration of 100 μg/mL. The antibacterial efficacy of AgNP-CM dispersion was evaluated over two E. faecalis strains: ATCC29212 and a wild strain collected from human necrotic teeth. 5% sodium hypochlorite (NaOCl) and sterile saline solution were used as positive and negative controls. 5 and 30-minute contact tests were conducted and each experimental group were replicated 10 times. After 24 hours of incubation, the Log CFU/mL were calculated. The AgNP obtained showed spherical shapes and had 30-60nm size. 5% NaOCl was able to completely eliminate both E. faecalis strains in all groups, showing a significant statistical difference when compared to AgNP-CM dispersion and negative control groups. AgNP-CM dispersion showed a statistically significant decrease in Log CFU/mL averages (p=0,0006) when compared to the sterile saline solution for the ATCC29212 strain during the 30-minute time. Between the 5-minute and 30-minute groups, a significant bacterial count decrease was also observed (p= 0,0128). The antibacterial efficacy of the dispersion was greater for the ATCC29212 strain than the wild strain, were the effect diminished. AgNP-CM dispersion showed a significantly lower antibacterial efficacy against E. faecalis than the 5% NaOCl at the tested times.