Resumen Este trabajo describe la degradación de etilenglicol en un sistema foto-Fenton heterogéneo. Se evaluó la actividad fotocatalítica de materiales sin dopar y dopados con Fe, preparados por los métodos sol-gel e impregnación húmeda-incipiente. Los ensayos se llevaron a cabo a diferentes valores iniciales de pH y concentración de H2O2. La fotoactividad de los materiales no dopados fue menor que la obtenida con aquellos dopados con Fe. Los valores óptimos para el pH y la concentración de H2O2 fueron 3,0 y 1.000 mg/L, respectivamente. El mayor porcentaje de degradación de etilenglicol (61 %) se logró con el material sintetizado por el método sol-gel. Dicho desempeño fotocatalítico se explicó con base en los resultados de caracterización estructural, morfológica y electrónica obtenidos por XRD, UV-vis DRX y XPS. De acuerdo con nuestro mejor conocimiento, este es el primer reporte relacionado con la degradación de etilenglicol usando TiO2 dopado con Fe en un sistema foto Fenton heterogéneo.

Abstract This work describes the ethylene glycol degradation in a photo-Fenton heterogeneous system. Iron-doped TiO2 photocatalysts prepared by different methods (incipient wet impregnation and sol-gel method), as well as the corresponding un-doped material were examined in this process. Different values of initial pH and H2O2 concentration were tested during the experiments. A lower photoactivity was observed for the un-doped materials than for the Fe-doped materials. Optimum results of initial pH and H2O2 concentrations were found to be 3.0 and 1,000 mg/L, respectively. Furthermore, the highest degradation percentage of ethylene glycol (61 %) was achieved for the material synthetized by sol-gel method. Such catalytic performance is explained on the basis of structural/morphological and electronic characterization results, reached by XRD, UV-vis DRS and XPS techniques. To the best of our knowledge, this is the first report related with the ethylene glycol degradation using Iron-doped TiO2 in a photo-Fenton heterogeneous system.

Resumo Este trabalho descreve a degradação do etilenoglicol em um sistema foto-Fenton heterogéneo. Fotocatalisadores de TiO2 dopados com ferro e preparados por diferentes métodos (impregnação incipiente do ponto úmido e método sol-gel), assim como o material não dopado correspondente foram examinados nesse processo. Diferentes valores iniciais de pH e de concentração de H2O2 foram testados durantes os experimentos. Uma fotoatividade mais baixa foi observada para os materiais não dopados em comparação aos materiais dopados de ferro. Os resultados ideais iniciais de pH e de concentração de H2O2 encontrados foram 3,0 e 1000 mg/L, respectivamente. Além disso, o percentual de degradação mais alto de etilenoglicol (61 %) foi alcançado para o material sintetizado pelo método sol-gel. Tal desempenho catalítico é explicado com base em resultados de caracterização estrutural/morfológica e eletrônica, alcançados por técnicas de XRD, UV-vis DRS e XPS. Dentro do nosso conhecimento, este é o primeiro relatório com respeito à degradação do etilenoglicol com uso de TiO2 dopado de ferro em um sistema foto-Fenton heterogéneo.

Abstract. One of the major public health problems worldwide is cancer followed by a significant number of deaths due to the resistance developed by bacteria or protozoan to the currently employed treatments. This generates an immediate need to develop drugs to treat these afflictions (illnesses, diseases). It has recently been identified that tumor cell, bacteria or protozoa are quite sensitive to oxidative stress induced by the same drugs. Due to this, it is important to develop new drugs to attend them, in this case, by using metals to increase the concentration of oxidative species. In the present work, the ligand 2,9-diformyl-4,7-diphenyl-1,10-phenanthroline and its corresponding coordination compounds with essential metals such as iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) were synthesized. The electrochemical study shows that these compounds present three redox processes, all of them associated to the ligand. The compounds have shown inhibitory activity in vitro against human neuroblastoma CHP-212 cells, Escherichia coli and trophozoites of Entamoeba histolytica HM1:IMSS. It has been found that the inhibitory activity of the compounds studied is related to the first reduction process of the ligand. The correlation between the inhibitory activity and the red ox potential was linear. The inhibitory activity in CHP-212 increased with the increase of the compounds’ redox potential values, in contrast with the behavior observed in Escherichia coli, where the compounds with lowest redox potential values have had significantly higher inhibitory activity. Many of these coordination compounds have shown a higher inhibitory activity than those typically used in the treatment of cancer (cisplatin). The next step is to prove these compounds in vitro against healthy cells in order to verify its selectivity or cytotoxicity in these systems.

Resumen. En recientes años, muchas bacterias han desarrollado resistencia ante las medicinas comúnmente utilizadas en el tratamiento. De igual forma una de las enfermedades que ha causado muchas muertes es el cáncer. Se ha demostrado que un punto en común para ambos sistemas es su susceptibilidad al estrés oxidante. Por esta razón es importante desarrollar nuevos medicamentos para el tratamiento utilizando metales esenciales generadores de estrés oxidante. En este trabajo se sintetizó y caracterizó el ligante 2,9-diformil-4,7-difenil-1,10-fenantrolina con sus correspondientes compuestos de coordinación con metales esenciales como hierro(II), cobalto(II), níquel(II), cobre(II) y zinc(II). Estos compuestos presentaron tres procesos redox asociados al ligante. Los compuestos presentaron actividad biológica in vitro en células CHP-212, Escherichia coli y trofozoitos de Entamoeba histolytica HM1:IMSS. Se encontró que la actividad biológica de estos compuestos está relacionada con el primer proceso redox del ligante. Mientras mayor fue el potencial de reducción en los compuestos, mayor actividad inhibitoria en las células CHP-212 y los compuestos con menores potenciales mostraron mayor actividad biológica en Escherichia coli. Muchos de estos compuestos presentaron una mayor actividad inhibitoria que aquellos comúnmente utilizados en el tratamiento del cáncer (cisplatino). El siguiente paso es evaluar estos compuestos in vitro, en células sanas para ver si estos compuestos son selectivos o citotóxicos.

Contamination with polycyclic aromatic hydrocarbons (PAHs) is considered an important health issue due to the toxicity of these compounds. Photocatalytic degradation of anthracene, a representative molecule of PAHs, using the high quantum yield semiconductor ZnO, has been reported. The solubility of anthracene in water makes necessary to use mixtures with organic solvents in fundamental degradation studies. It is well known that some organic solvents participate in the photochemical transformation of this molecule. In the PAHs photocatalysis, the competition between a semiconductor and solvents has not reported. Therefore, in this work, we decided to study the photocatalytic degradation of anthracene with two common reaction media and nanostructured ZnO. The semiconductor was obtained by a one pot method which consists in an alkaline hydrolysis of Zn(CH3COO)2·2H2O in ethanol. Nanoparticles size in colloidal dispersion was calculated using UV-Vis spectroscopy and High Resolution Transmission Electron Microcopy (HR-TEM). ZnO powder was isolated and characterized by X-ray diffraction to be used in photocatalytic experiments. Surface area determination and photocurrent spectroscopic experiments were also carried out. Linear sweep voltammetries under darkness and UV-Vis irradiation indicate a charge separation due to photoexcitation. Photocatalytic experiments in ethanol:water pH 12 (1:1) and acetone:water pH 12 (1:1), with and without ZnO was explored. The results demonstrated that ethanol:water and acetone:water promotes the photo-transformation of anthracene to 9,10-anthraquinone. Meanwhile, ZnO transformed anthracene to benzoic acid and to 9,10-anthraquinone in ethanol:water and acetone:water, respectively. A faster photochemical kinetic is observed when acetone was used as solvent in the presence and in the absence of ZnO.

In this work the electrochemical behavior of Co(II) complexes with substituted bidentate and tridentate polypyridine ligands [CoL3](BF4)2 and [CoL'2](NO3)2 in 0.1M phosphate buffer pH 7.2 was studied. A reversible electrochemical process Co(II)Ln →Co(III) Ln+1e- was observed. A linear relationship between the redox potential (E°) and the pKa of the non-coordinated ligand was found. It was demonstrated by DFT calculations the use of pKa value as a descriptor of the π acceptor character of a ligand. The electrochemical response in the presence of glucose oxidase (GOx) was also studied. It was possible to establish a tendency between the homogeneous electron transfer rate constant (ks) and the redox potential (E°) for the compounds studied in this work and other examples taken from the literature.

En este trabajo se estudió el comportamiento electroquímico de complejos de Co(II) con ligantes polipiridinicos bidentados y tridentados sustituidos [CoL3](BF4)2 y [CoL'2](NO3)2 en soluciones tampón de fosfato pH 7.2 0.1 M. Se observó un proceso electroquímico reversible Co(II)Ln → Co(III)Ln + 1e, encontrándose una relación lineal entre el potencial redox (E°) y el pKa del ligante no coordinado. Mediante cálculos DFT se demostró el uso del valor pKa como descriptor del carácter aceptor π de los ligantes. Se estudió la respuesta electroquímica en presencia de glucosa oxidasa (GOx). Se estableció una tendencia entre la constante de velocidad de transferencia de electrónica homogénea (ks) y el potencial redox (E°) para los compuestos estudiados en este trabajo y otros ejemplos tomados de la literatura.

In this work, two Ni(II) complexes with the tetradentate ligand N2S2 (pdto=1,8-bis(2-pyridyl)-3,6-dithioctane,) and the hexa-dentate ligand N6 (bdahp= 2,9-bis-(2',5'-diazahexanyl)-1,10-phenan-throline) were prepared in order to explore its electrochemical behavior, that indicate their potential use as molecular catalysts for the hydrogen evolution reaction. The Ni(II)-pdto complex presented two consecutive one electron transfer [Ni(II)-(pdto)] + 1e- [Ni(I)-(pdto)] and [Ni(I)-(pdto)] + 1 e- - Ni(0) + pdto. On the other hand the Ni(II)-bdahp complex presented the electrochemical reduction Ni(II)-(bdahp) + 1e- Ni(I)-(bdahp) followed by a coupled chemical reaction in an ECi mechanism, where a de-coordination of the diiminic moiety of the bdahp ligand was proposed. It was demonstrated that the pdto ligand promotes reduction over Ni(II) at less negative reduction potential in comparison when the ligand bdahp is presented.

En este trabajo se prepararon dos complejos de Ni(II) con un ligante tetradentado N2S2 (pdto=1,8-bis(2-piridil)-3,6-ditioctano) y un ligante hexadentado N6 (bdahp = 2,9-bis-(2',5'-diazahexani-l)-1,10-fenantrolina) con el fin de estudiar su comportamiento electroquímico que indique su potencial uso como catalizadores moleculares en la reacción de evolución de hidrógeno. El complejo Ni(II)-pdto presenta dos transferencias mono-electrónicas consecutivas [Ni(II)-(pdto)] + 1e- [Ni(I)-(pdto)] y [Ni(I)-(pdto)] + 1 e- - Ni(0) + pdto. Por otro lado el complejo Ni(II)-bdahp presentó la reducción electroquímica Ni(II)-(bdahp) + 1e- Ni(I)-(bdahp) seguida de una reacción química acoplada en un mecanismo de ECi, donde se propone una des-cordinación de la parte diimínica del ligante bdahp. Se demostró que el ligante pdto promueve la reducción del Ni(II) en potencial de reducción menos negativo en comparación cuando está presente el ligante bdahp.

This work presents the electrochemical characterization of Cu(NO3)2•2.5H2O, [Cu(pdto)H2O](PF6)2 and superoxide ion in DMSO. The electrochemical processes Cu(II) + 2e → Cu(0), [Cu(pdto)(H2O)]2+ + 1e → [Cu(pdto)]+, [Cu(pdto)]+ + 1e → Cu(0), O2 ↔ O2 + 1e-, and O2•- + 1e + H+ → OOH-were identified. The electrochemical response of a mixture of the complex [Cu(pdto)(H2O)]2+ with superoxide was studied and, according to this result, it was possible to establish a simple methodology that indicates if a compound presents a superoxide dismutase (SOD)-like mechanism.

En este trabajo se presenta la caracterización electroquímica de Cu(NO3)2•2.5H2O, [Cu(pdto)H2O](PF6)2 y del ion superóxido en DMSO. Se identificaron los procesos electroquímicos Cu(II) + 2e → Cu(0), [Cu(pdto)(H2O)]2+ + 1e → [Cu(pdto)]+, [Cu(pdto)]+ + 1e → Cu(0), O2•-↔ O2 + 1e-y O2•-+ 1e + H+ →OOH-. Posteriormente, se estudió la respuesta electroquímica de una mezcla del complejo [Cu(pdto)(H2O)]2+ con el ion superóxido y de acuerdo con este resultado, fue posible establecer una metodología sencilla que indica si un compuesto presenta un mecanismo tipo superoxido dismutasa, SOD.

In this paper we present spectroscopic and electrochemical studies of the chemical reaction between the salt Cu(NO3)2 2.5 H2O and the boron compound, monomercaptoundecahydro-closo-dodecaborate, [B12H11SH]2- in methanol. When the two substances were mixed a chemical reduction from Cu(II) to Cu(I) and an oxidation of the compound [B12H11SH]2- to [B12H11SSB12H11]4- were detected. The results obtained here may be useful in establishing a methodology to study the interaction of other metals with the compound [B12H11sH]2- in different solvents.

En este trabajo se presenta un estudio espectroscópico y electroquímico de la reacción química en metanol entre la sal Cu(NO3)2 2.5 H2O y el compuesto de boro, monomercaptoundecahidro-closo-dodecaborato [B12H11SH]2-. cuando las dos sustancias se mezclan se detecta una reducción química de Cu(II) a Cu(I) y la oxidación del compuesto [B12H11SH]2- a [B12H11SSB12H11]4-. Los resultados obtenidos aquí pueden ser útiles para establecer una metodología para estudiar la interacción de otros metales con el compuesto [B12H11SH]2-en diferentes disolventes.

Abstract Ferrocene derivatives have been used in the synthesis of polymeric materials with thermal resistance and nonlinear optical properties, and in the field of supramolecular electrochemistry as redox switching receptors. For these reasons, during the past few years the electrochemical studies on ferrocenyl derivatives have been growing up. In order to characterize molecules with potential uses in the synthesis of polymeric materials and to understand its electrochemical functioning, this paper presents electrochemical studies on these chemicals: 1) cis-diferrocenylethenes derivates (Isopropyl cis-2,3-Diferrocenylacrylate; 2) cis-2,3-Diferrocenylacrylic Acid; 3) cis-2,3-Diferrocenylacrylohydrazide; 4) cis-2,3-Diferrocenylacrylic Acid Piperidide; 5) cis-3,4-Diferrocenyl-2-methylbut-3-en-ol, and 6) cis-1,1-Diphehyl-2,3-Diferrocenylprop-2-en-1-ol. All of the chemicals presented two oxidation processes (l-ll), which were thought to be caused by the oxidation of the ferrocene groups, E1/2(l), E1/2(ll), ΔΕ1/2 (ll-l). The comproportionation constant Kcom was calculated. According to this value, it can be proposed that the molecules containing a carbonyl group (1-4) present larger electronic communication compared to molecules with a hydroxy group (5-6). Uv-vis espectra of all compounds in butironitrile solution were obtained. A correlation between Kcom and λ max was also observed.

Resumen Los derivados del Ferroceno han sido empleados en la síntesis de materiales poliméricos con resistencia térmica y con propiedades ópticas no lineales y en el campo de la electroquímica supramolecular como receptores de interruptores redox. Por estas razones los estudios electroquímicos de los derivados ferrocenil se han incrementado en los últimos años. Con la finalidad de caracterizar moléculas con potenciales usos en la síntesis de materiales poliméricos y entender su comportamiento electroquímico, este trabajo presenta estudios electroquímicos de derivados cis-diferroceniletenos (cis-2,3-Diferrocenilacrilato de isopropiio (1), Ácido cis-2,3-Diferrocenilacrílico (2), cis-2,3-Diferrocenilacrilohidrazida (3), Piperidina del Ácido cis-2,3-Diferrocenilacrílico (4), cis-3,4-Diferrocenil-2-metilbut-3-en-ol (5), cis-1,1-Difenil-2,3-Diferrocenilprop-2-en-1-01 (6). Todos los compuestos presentan dos procesos de oxidación (l-ll), atribuidos a la oxidación de los dos ferrocenos , E1/2(l), E1/2(ll), ΔΕ1/2 (ll-l). Se calcula la constante de desproporción Kcom. De este valor se propone que las moléculas que contienen el grupo carbonilo (1-4) presentan una gran comunicación electronica comparada con las moléculas que contiene un grupo hidroxil (5-6). El espectro UV-vis de todos los compuestos se obtuvo en butironitrilo. Se encontró también una correlación entre Kcom y λ max .

Este trabalho descreve a síntese e caracterização dos ligantes não simétricos CH3SCH2CH2SRf (Rf = C6F5, C6HF4-4, C6H4F-2, C6H4F-3, C6H4F-4) bem como seus derivados de platina(II) cis-[PtCl2(CH3SCH2CH2SR f)] (Rf = C6F5, C6HF4-4, C6H4F-2, C6H4F-3, C6H4F-4) e trans-[PtCl2(CH3SCH2CH 2SRf)2] (Rf = C6F5, C6HF4-4). O espectro de RMN de 19F desses complexos mostra os isômeros syn e anti, consistente com um rápido dobramento do anel metalacíclico e uma inversão lenta de configuração nos átomos de enxofre do tioéter. As estruturas molecular e cristalina dos compostos cis-[PtCl2(CH3SCH2CH2SC 6F5)], cis-[PtCl2(CH3SCH2CH2SC 6H4F-3)] e trans-[PtCl2(CH3SCH2CH 2SC6F5)2], resolvida por difração de raios-X, são também descritas.

This paper describes the synthesis and characterization of the non-symmetric ligands CH3SCH2CH2SRf (Rf = C6F5, C6HF4-4, C6H4F-2, C6H4F-3, C6H4F-4) as well as their platinum(II) derivatives cis-[PtCl2(CH3SCH2CH2SR f)] (Rf = C6F5, C6HF4-4, C6H4F-2, C6H4F-3, C6H4F-4) and trans-[PtCl2(CH3SCH2CH 2SRf)2] (Rf = C6F5, C6HF4-4). 19F NMR of these complexes show the presence of syn and anti isomers, consistent with a fast flipping of the metallacycle ring and a slow inversion of configuration at the dithioether sulfur atoms. The molecular and crystalline structures of the compounds cis-[PtCl2(CH3SCH2CH2SC 6F5)], cis-[PtCl2(CH3SCH2CH2SC 6H4F-3)] and trans-[PtCl2(CH3SCH2CH 2SC6F5)2], solved by X-ray diffraction are also described.