Antonio Eduardo Da Hora Machado

Universidade Federal de Uberlândia (UFU) | UFU · Institute of Chemistry (IQ)

Solar driven semiconductor-based photoreforming of biomass derivatives, such as glycerol is a sustainable alternative towards green hydrogen evolution concerted with production of chemical feedstocks. In this work, we have investigated the influence of the pH of the hydrothermal treatment on the efficiency of Bi2WO6 as photocatalyst in the glycerol...

p-aminobenzoic acid is a substance widely used in several areas, such as catalysis, biomarkers, magnetic materials, luminescent materials and biological applications. p-aminobenzoate complexes with alkaline earth metal were synthesized and the thermal and pyrolysis behavior was studied using thermoanalytical and spectroscopic techniques. Based on T...

The monometallic complex [Pd(L)(PPh3)] (mono‐Pd) was synthesized using a potentially tridentate hydrazone (H2L) and used as precursor to prepare a heterobimetallic ruthenium (II)‐palladium (II) complex [Cl2(p‐cymene)Ru(μ‐L)Pd (PPh3)] (Ru‐Pd). Mono‐Pd and Ru‐Pd were characterized by fourier transform infrared spectroscopy (FTIR), ultraviolet‐visible...

Three new cobalt(II) complexes with non-symmetrically-substituted N2O2 tetradentate Schiff-base ligands, prepared from the 1:1:1 condensation of 3-etoxy-salicylaldehyde, salicylaldehyde and ethylenediamine (H2Etsal − 1), o-phenylenediamine (H2Phsal − 2) or 1,2-cis,trans-cyclohexyldiamine (H2Cysal − 3), were synthesized. The complexes 1–3 were chara...

Excited-state absorption (ESA) portraits a new pathway to controllably generate hexaprotonated (H8TPyP⁶⁺) porphyrins followed by the formation of a new species (possibly porphyrin aggregate) departing from pristine meso-(4-pyridyl) porphyrins (H2TPyP) dissolved in chloroform (CHCl3). Steady-state absorption and photoluminescence (PL) spectroscopies...

A series of iminochalcones derived from 3-(4-aminophenyl)-1-(4-hydroxyphenyl)prop-2-en-1-one, were synthesized using different p-substituted benzaldehydes (R = –N(CH3)2 (2a), –H (2b) and –NO2 (2c)). The melting points of these compounds depend on the substituent (2c > 2a > 2b) as a function of the intermolecular interactions. The absorption spectra...

In this work, the emission properties of fac-[Re(CO) 3 (NN)(py)] + , NN = 1,10-phenanthroline (phen), dipyrido[3,2-f:2',3'-h]quinoxaline (dpq) and dipyrido[3,2-a:2'3'-c]phenazine (dppz); py = pyridine were investigated in different temperatures, ranging from 80 to 300 K, and in different solvent mixtures and in polymethyl methacrylate. The changes...

A new ruthenium polypyridyl complex, [Ru(bpy)2(acpy)]+ (acpy = 2-pyridylacetate, bpy = 2,2’-bipyridine), was synthesized and fully characterized. Distinct from the previously reported analog, [Ru(bpy)2(pic)]+ (pic = 2-pyridylcarboxylate), the new complex...

In this study, we synthesized the complex [Co(BuSalen)] using the novel tetradentate BuSalen ligand and analyzed its ability as a controlling agent for the photo-induced organometallic-mediated radical polymerization (photo-OMRP) of butyl acrylate (BA) using diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) as photo-initiator. BA polymerization...

In this study, results are presented concerning the development of alternative materials based on titanium dioxide (TiO2) and agro-industrial waste for use in the treatment of effluent contaminated with dyes. The photocatalytic activity of a composite formed by the association of activated carbon, obtained from pit residue of mango, with modified t...

Monometallic [RuCl 2 (η ⁶ - p -cymene)(pipNH 2 )] (mono-Ru) and heterobimetallic [RuCl 2 ( p -cymene)](μ-Schiff-pip)Ni(PPh 3 )Cl] ( Ru-Ni ) complexes were successfully synthesized. They were fully characterized by FTIR, UV-Vis, and NMR spectroscopic studies, elemental analysis, cyclic voltammetry and computational studies. Complex...

TiO 2 nanoparticles were successfully synthesized by the sol-gel method employing different glycols (ethylene glycol, diethylene glycol or polyethylene glycol 300), which were heat-treated in conventional oven or by hydrothermal via, obtaining photocatalysts with particle sizes and distinct crystalline structures. HRTEM analyses showed that the oxi...

The manganese Schiff-base complexes were applied in the OMRP of vinyl acetate.

New photocatalysts based on TiO 2 were synthesized and characterized. The synthesis involved the controlled hydrolysis of titanium tetraisopropoxide using water containing different proportions of acetone. X-ray diffraction analyses combined with Raman spectroscopy revealed crystalline oxides characterized by the coexistence of the anatase and broo...

Arene-ruthenium complexes of type [RuCl2(p-cymene)(cyclo-alkylamine)], where alkyl is pentyl (1), hexyl (2), heptyl (3) or octyl (4), were successful synthetized and applied as pre-catalysts in ROMP of norbornene (NBE). From experiments as a function of temperature and NBE loads, the yields increased with increasing cyclo-alkyl ring size (4 > 3 > 2...

A series of cobalt(II)-α-diimine complexes derived from cycloalkylamines (cycloalkyl = cyclopentyl (1a), cyclohexyl (1b), cycloheptyl (1c), and cyclooctyl (1d)) were synthesized: [CoCl2(Pent-DAB)] (2a), [CoCl2(Hex-DAB)] (2b), [CoCl2(Hept-DAB)] (2c), and [CoCl2(Oct-DAB)] (2d). The α-diimines 1a-d were characterized by FTIR, UV–Vis, and ¹H- and ¹³C N...

Reactions of thiosemicarbazone ligands (H2L¹) with [ReX3(NPh)(PPh3)2] (X = Cl or Br) led to the formation of stable rhenium(V) complexes of composition [ReX(NPh)(HL1)(PPh3)]X. The Re(V) complexes have been characterized by diverse techniques including FTIR, ¹H and ³¹P NMR, elemental analysis, HRMS and single-crystal X-ray diffraction analysis. The...

Reaction of the precursor cis,fac-[RuCl2(dmso-S)3(dmso-O)] with three carbazate ligands led to new compounds of the type cis,fac-[RuCl2(dmso-S)3(L)] (L = benzylcarbazate (bc), 1; 4-methoxybenzylcarbazate (mc), 2; or 3,5-dimethoxy-α,α-dimethylbenzylcarbazate (mmc), 3). Complexes 1–3 have been characterized by elemental analysis (CHN), FTIR, UV–vis,...

This work describes the preparation of a new thiosemicarbazone derivative, (Z)-N-ethyl-2-(6-oxo-1,10-phenanthrolin-5(6H)-ylidene)hydrazinecarbothioamide (phet) and its respective Re(I) tricarbonyl chloro complex, fac-[ReCl(CO)3(phet)]. The spectroscopic, photophysical and electrochemical properties of the new complex...

[PtCl2(phen)] reacts with thiosemicarbazones derived from β-diketones (H2LR) leading to an intramolecular C–C coupling between phen and the ketone upon formation of the tetracoordinated N,N,N,S chelates [PtII(phenLR)]. The reactions proceed...

Arene ruthenium(II) complexes bearing the cyclic amines RuCl2(η⁶‐p‐cymene)(pyrrolidine)] (1), [RuCl2(η⁶‐p‐cymene)(piperidine)] (2), and [RuCl2(η⁶‐p‐cymene)(peridroazepine)] (3) were successfully synthesized. Complexes 1–3 were fully characterized by means of Fourier transform infrared, UV–visible, and NMR spectroscopy, elemental analysis, cyclic vo...

The role of meso-substituents on the spectral features of free-base porphyrins is explored. Meso-tetra(4-pyridyl)porphyrin is compared with meso-tetra(2-thienyl)porphyrin and meso-tetra(pentafluorophenyl)porphyrin. Our results indicate that some of the asymmetric Q-bands in the free-base porphyrin tend to become symmetric relative to the adopted me...

Chloramphenicol (CAP) has been detected in aqueous matrices as a consequence of its incomplete removal during the conventional treatments applied in sewage treatment plants 1. Its presence may harm aquatic environments 2 , it being, therefore, imperative to evaluate and propose effective alternatives for the treatment of aqueous matrices containing...

Nickel(II) complexes of Schiff base derived from cycloalkylamines (cycloalkyl = cyclopentyl (cpen), cyclohexyl (chex), and cycloheptyl (chep)) were synthesized: [NiII(Lcpen)2] (1), [NiII(Lchex)2] (2), and [NiII(Lchep)2] (3). The Schiff base-NiII complexes 1-3 were characterized by FTIR, UV–Vis, elemental analysis, and computational methods. Electro...

A series of [RuCl(dppb)(μ-Cl)3Ru(dppb)(amine)] complexes, where amine is pyrrolidine (1), piperidine (2) or perhydroazepine (3), were synthesized and characterized by elemental analysis, FTIR, UV–Vis, and ¹H, ¹³C{¹H} and ³¹P{¹H} NMR spectroscopy. The electrochemistry properties of the complexes 1–3 were investigated by cyclic voltammetry and exhibi...

A series of mononuclear complexes has been synthesized by reactions of group 10 metal ions with bis(4-phenyl-3-thiosemicarbazone) (H2bPht), affording compounds of general formula [MII(bPht)] (M = Ni, Pd and Pt). Their characterization involved FTIR, UV–Vis, 1H NMR, CV, DPV and elemental analysis. Furthermore, the crystal structures of all complexes...

In this work are presented and discussed the results related to the obtaining of the best conditions for the treatment of a real paint wastewater by combining the chemical coagulation methods and solar photo-Fenton process. The best conditions for the coagulation-flocculation process involved the use of 8 mL of chemical coagulant (ferric chloride)...

Almost spherical SiO2 nanoparticles were recovered by thin films of TiO2 (highly crystalline anatase) produced in situ sol-gel syntheses. Silica coating was proven by scanning electron microscopy and infrared measurements. The outstanding photocatalytic efficiency of this material was proven by the degradation of the dye Ponceau 4R (P4R) in aqueous...

Novel dimethyl sulfoxide ruthenium(II) complexes of N-heterocyclic carbenes [RuCl2(S-dmso)2(SIMes)] (1), [RuCl2(S-dmso)2(IMes)], (2) [RuCl2(S-dmso)2(SIDip)] (3), and [RuCl2(S-dmso)2(IDip)] (4) were successfully synthesized. The complexes 1-4 were characterized by elemental analysis, FTIR, UV-Vis, 1H and 13C NMR, and computational studies. The polyn...

The changing of the electronic and vibronic states due to the insertion of Zn(II), Cu(II), Ni(II) or Co(II) ions in the meso-tetrakis(4-pyridyl)porphyrin ring center is investigated. The combination of absorption, photoluminescence, Raman and infrared spectroscopies with second-derivative-based spectral deconvolution analysis reveals that the struc...

Leishmaniasis, a neglected tropical disease caused by protozoans of the genus Leishmania, kills around 20–30 thousand people in Africa, Asia, and Latin America annually and, despite its potential lethality, it can be treated and eventually cured. However, the current treatments are limited owing to severe side effects and resistance development by...

A systematic study concerning about the vibronic structure of the 5,10,15,20-meso-tetra(pyridyl)-21H,23H-porphyrin (H2TPyP) is presented aiming to elucidate its spectroscopic features. Beyond the assignments reported in the literature, we elaborate, by means of the Voigt and Gaussian deconvolutions, new interpretations for the porphyrin´s Qx region...

A series of new cobalt(II) complexes of Schiff base derived from salicylaldehyde and different cycloalkylamines (cycloalkyl = cyclopentyl-1a, cyclohexyl-1b, and cycloheptyl-1c) was synthesized: [Co(CyPen-Salicyl)2] (2a), [Co(CyHex-Salicyl)2] (2b), and [Co(CyHep-Salicyl)2] (2c). The bis(phenoxyiminato)Co(II) complexes (2a-2c) have been fully charact...

Heterogeneous photocatalysis using titanium dioxide as catalyst is an attractive advanced oxidation process due to its high chemical stability, good performance and low cost. When immobilized in a supporting material, additional benefits are achieved in the treatment. The purpose of this study was to develop a simple protocol for impregnation of Ti...

Schematic drawing of photodegradation experiments (1) beaker; (2) magnetic stirrer; (3) peristaltic pump; (4) CPC reactor (collector and borosilicate glass tube); and (5) solar spectrum simulated lamp.

In this work, a novel complex fac-[Re(CO)3(dcbH2)(trans-stpy)]+, (dcbH2= 4,4'-dicarboxylic acid-2,2'-bipyridine; trans-stpy = trans-4-styrylpyridine) was synthesized and characterized toward its spectroscopic, photochemical, and photophysical properties. The experimental data provide new insights on the mechanism of photochemical trans-to-cis isome...

Ciprofloxacin has been determined with high frequency in studies involving environmental waters matrixes. However, no study evaluating the correlation between the initial pH and molar iron/organic ligand ratio has been published. This paper describes the degradation of the antibiotic ciprofloxacin by the photo-Fenton process using different sources...

This paper describes the degradation of the antibiotic chloramphenicol by a photo-Fenton process under artificial and solar irradiation. Using artificial radiation, the role of different sources and concentrations of iron (salts of Fe²⁺ and Fe³⁺ and the iron complexes citrate (FeCit) and oxalate (FeOx)), initial pH, concentration of H2O2 and additi...

Reactions of p-toluenesulfohydrazide with R-isothiocyanates afford new ligands containing both the sulfonamide and thiosemicarbazide moieties (LR: R=cyclohexyl (Cy) or phenyl (Ph)). LR reacts with AgNO3 in EtOH in a 2:1 M ratio leading to formation of colourless Ag(I) complexes of general formula [Ag(LR)2]NO3. The crystal structure of a representat...

The feasibility of biodiesel effluent treatment combining coagulation-flocculation with a photolytic process was evaluated, being the photolytic process involving the irradiation of the effluent by UV-C, or by UV-C irradiation with simultaneous addition of H2O2 (H2O2/UV-C). The coagulation-flocculation was performed at the natural pH of the effluen...

This study describes the synthesis and characterization of three α-diimine-cobalt complexes of the type [CoCl2(R-DAB)] (R-DAB = R–N[dbnd]CH–CH[dbnd]N–R; R = Mes, Dipp and Dipp∗) and their application as mediators for the cobalt-mediated radical polymerization (CMRP) of vinyl acetate (VAc) using 2,2′-Azobis(2-methylpropionitrile) (AIBN) as initiator...

In this work, excitation and emission spectra were evaluated in order to elucidate the properties of quinguangulin and rubrofusarin in water/ethanol mixture. The study demonstrates that the maximum excitation wavelength can be significantly modulated changing the proportion of organic solvent in the water/organic solvent system. Quinquangulin prese...

Pharmaceuticals have been detected and quantified in surface, groundwater and drinking water. Although present in low concentrations, they may contribute to the development of deleterious effects on non-target organisms. Thus, new technologies for the treatment of effluents containing this type of pollutant must be evaluated. In this context, the o...

This study reports a protocol for the treatment of a sanitary landfill leachate through integration between a stage of coagulation-flocculation, a step of filtration of the resulting suspension, and application of the photo-Fenton process using a ferrioxalate complex and solar irradiation. The best results for turbidity removal by coagulation-flocc...

In the present work the influence of the distance of the protonatable site of different ancillary ligands to the metal center on the luminescence quenching of ReI polypyridyl complexes by hydroquinone are evaluated by means of experimental and theoretical studies. In these systems, it is expected the occurrence of proton-coupled electron transfer (...

Ruthenium(II) complexes of Schiff base derived from cycloalkylamines (cycloalkyl = cyclopentyl (1a), cyclohexyl (1b), cycloheptyl (1c), and cyclooctyl) (1d) were synthesized: [RuCl(CyPen-Salen)(PPh3)2] (2a), [RuCl(CyHex-Salen)(PPh3)2] (2b), [RuCl(CyHep-Salen)(PPh3)2] (2c), and [RuCl(CyOct-Salen)(PPh3)2] (2d). The Schiff base-RuII complexes 2a-d wer...

Kojic acid (KA) is an organic acid widely used in pharmaceutical industry, mainly as a skin lightening agent. Based on the ability of KA to form complexes with ions, we found the most possible kind of complex formed with cation aluminum. KA-Al³⁺ complex structures were studied using potentiometric and spectrophotometric (UV) titrations, FTIR and ¹³...

The past decades have witnessed great research efforts based on nanotechnology and molecular engineering for the development of photo-induced devices, aiming at conversion of solar energy into electricity and fuels as well as the use of solar light for environmental remediation. The main challenge of this exciting field is to find suitable ways of...

The role of different operational parameters related to Fenton reactions (pH, concentration of Fe(2+) and H2O2, and reaction time) and of Cl(-) and SO 4 (-) was investigated in the degradation of the azo dye Direct Red 81, expressed in terms of its decolorization. The factorial design and Pareto's charts showed that only Fe(2+) concentration and pH...

In the present study we estimated the Critical Micelle Concentration (CMC) of Triton X-100 in an aqueous buffered medium (PBS buffer, pH 7.4), using 3-(benzoxazol-2-yl)-7-(N,N-diethylamino)chromen-2-one (BDC), a push-pull compound, as extrinsic fluorescence probe. The CMC value found, 0.33 mmol L-1, shows good agreement with data from literature ob...

In this work it was studied the degradation of the insecticide fipronil (FIP) by heterogeneous photocatalysis induced by TiO2 P25. Using chemometric methods (Factorial Design and Response Surface Methodology), it was possible to evaluate the role of interaction between pH of the reaction medium, the reaction time and concentration of TiO2, optimizi...

The conditions for treatment of a biodiesel effluent, combining coagulation-flocculation and membrane filtration with Fenton/photo-Fenton reactions, in order to ensure the reuse of water, are presented in this work. Coagulation-flocculation and membrane filtration were applied as a first stage to remove the turbidity, suspended solids, apparent col...

This paper describes the development of a biosensor to detect neurodegenerative diseases, focusing on Alzheimer’s disease, the most common type of dementia, based on the use of a small protein-like chain designed to mimic a peptide that recognizes glutamate, the main excitatory neurotransmitter present in the central nervous system of mammals. This...

Laser flash photolysis (LFP) studies have been performed in order to investigate the triplet reactivity toward hydrogen and electron donors of the benzo-fused furan psoralens 3-ethoxycarbonyl-2H-benzofuro[2,3-e]-1-benzopyran-2-one (1) and 3-ethoxycarbonyl-2H-benzofuro[3,2-d]-1-benzopyran-2-one (2). Photolysis of the psoralens 1 and 2 results in the...

The photocatalytic performance of a composite based on the association of TiO2 and 2.5wt% of Zinc (II) Phthalocyanine, TiO2/ZnPc, was evaluated towards the mineralization of paracetamol and compared to that observed for the bare oxide in different pHs and H2O2 concentrations. The results show that the photocatalytic performances were influenced by...

In this study it was evaluated the role of the composition of sanitary landfill leachate on the removal of dissolved organic carbon (DOC) by photo-Fenton process. The composition of the matrix (high turbidity and color, as well as presence of inorganic ions sulfate and chloride) does not reduce the efficiency of DOC removal by photo-Fenton reaction...

The preparation of titanium dioxide nanoparticles doped with nitrogen for application as photocatalyst in the decomposition of azo dyes was optimized by factorial planning. Five variables were evaluated and the results showed that the stirring method of the reaction medium, the nitrogen source and the calcination temperature are the determining par...

In this study the coagulation-flocculation process was evaluated as an alternative for treatment of biodiesel wastewater. The role of two coagulants, Al 3+ and Fe 3+ , as well as its dosage, pH, treatment time, stirring and aeration were evaluated. It was observed that in the treatment using Al 3+ the pH of the effluent (9.7) does not need to be ad...