Complexos macrocíclicos polinucleares mediados por ponte cianeto. Síntese, caracterização e aplicações em química supramolecular

Orientador : Prof. Dr. Fábio Souza NunesDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciencias Exatas, Programa de Pós-Graduação em Química. Defesa: Curitiba, 25/03/2011Inclui bibliografiaResumo: Dentro da Quimica, os compostos de coordenacao tem encontrado grande campo de atuacao, principalmente por oferecerem caracteristicas unicas, aliadas a flexibilidade de estados de oxidacao e estabilidade dos ions metalicos, na obtencao de materiais com diversas propriedades eletronicas, opticas, magneticas e biologicas. Os cianometalato-complexos, os quais possuem o cianeto como ligante-ponte, sao os mais investigados dentre as estruturas supramoleculares baseadas em interacoes metalicas. Com a finalidade de preparar compostos polinucleares, os ligantes macrociclicos sao interessantes porque bloqueiam as posicoes equatoriais, viabilizando interacoes apenas na regiao axial, possibilitando, assim, a obtencao de fios moleculares. Neste sentido, justifica-se o uso do ligante binuclear macrociclico tetraiminodifenolico (tidf) como bloco construtor. Foram preparados, com a finalidade de obtencao de complexos polinucleares, dois complexos macrociclicos binucleares [Cu2(tidf)(ClO4)2(H2O)2] e [Co2(tidf)(ClO4)2(H2O)2], sendo este ultimo inedito na literatura. Utilizando estes dois complexos, juntamente com cianometalatos diversos, foram obtidos tres complexos ineditos, [{Cu2(tidf)(OH2)}2(ƒÊ-CN)2{Fe(CN)4}] E12H2O, [Cu2(tidf)(H2O)2][Fe(CN)5NO] EH2O e [Cu2(tidf)(H2O)2][Ni(CN)4], o primeiro pentanuclear e os seguintes trinucleares. Os tres complexos sao produtos das reacoes do complexo [Cu2(tidf)(ClO4)2(H2O)2] com os cianometalatos K4[Fe(CN)6] E3H2O, K4[Ni(CN)4] e Na2[Fe(CN)5NO].2H2O. O complexo pentanuclear apresenta o ligante cianeto como ponte entre os centros de cobre(II) e ferro(II). Ja os complexos trinucleares, apresentam os ligantes cianeto interagindo com moleculas de agua por ligacao de hidrogenio, formando estruturas supramoleculares em que a comunicacao entre o complexo macrociclico e o cianometalato e mediada por esse tipo de interacao. Todos os complexos obtidos formaram cristais susceptiveis a difracao de raios X. Alem disso, todos os complexos obtidos, alem dos seus precursores, foram caracterizados por tecnicas de Espectroscopia na regiao do UV-Visivel e Infravermelho, Ressonancia Paramagnetica Eletronica e Ressonancia Magnetica Nuclear, Espectroeletroquimica e Voltametria Ciclica, Analise Elementar e Medidas de Magnetismo Molecular. Os valores de constante de acoplamento magnetico, J, mostraram uma forte interacao intermetalica entre os centros atraves da ponte fenolato. Esta interacao e forte o suficiente para mascarar efeitos magneticos derivados da interacao entre os metais atraves da ponte cianeto. As propriedades espectrais correlacionaram-se com as distorcoes estruturais exibidas pelos dados cristalograficos e os resultados foram racionalizados com base na teoria de campo cristalino.Abstract: In chemistry coordination compounds have been intensively studied because they offer unique features, combined with the flexibility of metal ions and stability of oxidation states, to obtain materials with different electronic, optical, magnetic and biological properties. The cianometalato-complexes, which have the cyanide as bridging ligand, are among the most investigated supramolecular structures based on interactions between metal ions. In order to prepare polynuclear compounds, macrocyclic ligands are interesting because they block the equatorial positions, and favor axial substitution, thus enabling the achievement of molecular wires. In this sense, we have used binucleant macrocyclic ligand tetraiminodifenolico (tidf) as a building block. Two binuclear complexes [Cu2(tidf)(ClO4)2(H2O)2] and [Co2(tidf)(ClO4)2(H2O)2] were prepared, the latter being unique in the literature. Using these two complexes, along with several cyanide-metal complexes three new complexes were prepared, [{Cu2(tidf)(OH2)}2(ƒÊ-CN)2{Fe(CN)4}].12H2O, [Cu2(tidf)(H2O)2][Fe(CN)5NO] EH2O and [Cu2(tidf)(H2O)2][Ni(CN)4]. The first one is pentanuclear and the others are trinuclear. The three complexes are products of the reactions of the complex [Cu2(tidf)(ClO4)2(H2O)2] with the cianometalatos K4[Fe(CN)6].3H2O, K4[Ni(CN)4] and Na2[Fe(CN)5NO].2H2O. The pentanuclear complex features the cyanide ligand as a bridge between the centers of copper(II) and iron(II). The crystal structure of both trinuclear complexes showed hydrogen bonding between water molecules and the cyanides to form supramolecular architetures. All complexes, and their precursors, were characterized by Spectroscopy in the UV-Visible and Infrared, Electronic Paramagnetic Resonance and Nuclear Magnetic Resonance, Spectroelectrochemistry and Cyclic Voltammetry, Elemental Analysis and Measures of Molecular Magnetism. Calculated magnetic coupling constant, J, is consistent with a strong intermetallic communication through the phenolate bridge, a phenomenon strong enough to mask any other relevant magnetic property. UV-vis data were interpreted based on crystal field theory and the energy of the transitions were correlated with structural distortions of the compounds

Adenine and Thymine Effect on Quartz Dissolution at Different Artificial Seawaters

According to Bernal (1951) minerals may have played important roles in the origin of life such as: protect biomolecules against degradation by UV radiation or hydrolysis, pre-concentrate biomolecules from prebiotic seas and formation of polymers. Today quartz is widely distributed on Earth as well as was widely distributed on the prebiotic Earth. There are several works showing the quartz dissolution, this work shows for the first time, quartz dissolution under prebiotic chemistry conditions. The experiments were carried out with and without adenine and thymine dissolved in several artificial seawaters, distilled water and alkaline distilled water (pH = 11.0). It should be noted that seawater 4.0 Ga resembles the major cations and anions of the sea of the prebiotic Earth. The quantification of dissolved quartz in different seawater, the measurement of pH and of conductivity were performed daily for a 35 day period, at a controlled temperature (30 °C). The dissolution was dependent of water salinity and especially of pH. Depending on the artificial seawater, adenine and thymine can either accelerate the quartz dissolution or protect it. DOI: http://dx.doi.org/10.17807/orbital.v10i6.1152

In-situ direct synthesis of HKUST-1 in wool fabric for the improvement of antibacterial properties

The use of Metal-Organic Frameworks (MOF) such as HKUST-1 in textiles is an alternative with regard to the development of technologies that are increasingly seeking for functionalities, mainly in the fields of health and hygiene, named biofunctional fabrics. However, the application of the MOF under the surface of the wool fiber can lead to a low durability finish due to its low fixation. Thus, this project aims to perform the direct synthesis of HKUST in the wool fiber, so that a product with good washing durability can be obtained. The purpose of this study was to incorporate metal-organic frameworks, composed of copper and trimesic acid, into woolen fabrics, to improve the antibacterial properties. The synthesis was performed directly in the wool fabric, at time intervals of 24 and 48 h. The resulting fabrics were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Diffractometry (XRD), Fourier Transform Spectroscopy Infrared-Attenuated Total Reflectance (FTIR-ATR), and colorimetric analysis (CIElab), and the Antimicrobial Activity Test (American Association of Textile Chemist and Colourists - AATCC Test Method 61-2007-2A) was performed. The results suggested that the application produced textiles with antibacterial properties, showing activity against Escherichia coli.Peer ReviewedPostprint (published version

ß-Cyclodextrin: Disperse yellow 211 complexes improve coloristic intensity of polyamide dyed knits

Dyes are complex molecules that can sometimes cause damage to the aquatic environment and harm human health. They are often not completely removed from effluent by the usual treatments; therefore, efforts have been made to increase their exhaustion from dyeing through chemical and physical processes. In this context, the use of ß-cyclodextrin (ß-CD) as dyeing auxiliary agent promotes the reduction of harmful products, also increasing the color intensity of the fabric. In this paper, ß-CD was used as a complexing agent to dye polyamide (PA) using the dye C.I. Disperse Yellow 211 (DY211) in order to improve dye exhaustion and color intensity using the ß-CD:DY211 complex. The conventional dyeing process and ß-CD:DY211 dyeing process by exhaustion were compared, and adsorption kinetics, isotherms, and the coloristic intensity were evaluated. The chemical shifts in the FTIR spectra and the thermal stability evidenced the formation of the ß-CD:DY211 complex. Regarding dyeing kinetics and isotherm, the pseudo-first-order model was the most appropriate to describe the process, while Nernst isotherm was the one that best represented the adsorption results. Categorically, the samples dyed with the ß-CD:DY211 complex obtained higher coloristic intensity in comparison with the conventional process. With this evidence, it is possible to conclude that cyclodextrin is a suitable replacement for environmentally harmful textile aides without adding further steps into the dyeing process or the need for additional equipmentPostprint (author's final draft

Supramolecular assembly of new heteropolymetalic molecules based on tetraiminodiphenolate macrocycle and hexacyanometallate anions: magnetostructural and spectroscopic properties

Herein we report on the synthesis, single crystal X-ray structure, spectroscopic and magnetic properties of [{Cu2(tidf)(H2O)}2(μ-CN)2Fe(CN)4]·6H2O (1), [Cu2(tidf)(H2O)2][Ni(CN)4] (2) and [Cu2(tidf)(H2O)2][Fe(CN)5NO]·H2O (3) (tidf = a Robson type macrocyclic ligand obtained on condensation of 2,6-diformyl-4-methylphenol and 1,3-diaminopropane). Complex (1) is pentanuclear; two paramagnetic dicopper(II) units are linked by a hexacyanoferrate(II) ion through two cyano-bridges. All compounds exhibit extensive, three-dimensional, supramolecular structures supported by classic hydrogen bonding between the coordinated aqua ligands, water molecules and cyano groups. Magnetism as a function of the temperature of complexes 1-3 is consistent with a strong antiferromagnetism with exchange parameters 2J estimated -783(29), -913(2), -905(1), respectively.CNPqFINEP (CT-Infra 03/2001)BBSR

Direct synthesis of HKUST-1 onto cotton fabrics and properties

Metal-organic frameworks are crystalline nanostructures formed by a metal interspersed by an organic binder. These metal-organic materials are examples of nanomaterials applied to textile material in search of new functionalized textiles. Cotton is a cellulosic fiber of great commercial importance, and has good absorption capacity and breathability; however, due to these characteristics, it is susceptible to the development of microorganisms on its surface. This work aims to analyze how the direct synthesis of HKUST-1 in cotton fabric modifies the chemical and physical properties. The material obtained was characterized by scanning electron microscopy to obtain its morphology, by spectrophotometry CIE L*a*b* to verify the color change, by a biological test to verify its resistance to microorganisms and, finally, by a unidirectional traction test to verify the change in its mechanical resistance. Thereby, it was possible to observe the formation of MOFs with the morphology of nanorods, and also, with regard to HKUST-1 in the cotton fabric, when applied, an elimination percentage higher than 99% was observed for both bacteria, E. coli and S. aureus. The presence of MOF was detected even after washing, however, the loss of 75% in the mechanical resistance of the material makes its potential for textile finishing unworkable.Peer ReviewedPostprint (published version

Reply to Nayak, P.K. Comment on “Samulewski et al. Magnetite Synthesis in the Presence of Cyanide or Thiocyanate under Prebiotic Chemistry Conditions. Life 2020, 10, 34”

We have considered the criticisms raised by Pranaba K. Nayak [...

Magnetite Synthesis in the Presence of Cyanide or Thiocyanate under Prebiotic Chemistry Conditions

Magnetite is an iron oxide mineral component of primitive Earth. It is naturally synthesized in different ways, such as magma cooling as well as olivine decomposition under hydrothermal conditions. It is probable magnetite played a significant role in biogenesis. The seawater used in the current work contained high Mg2+, Ca2+ and SO42− concentrations, unlike the seawater of today that has high Na+ and Cl− concentrations. It is likely that this seawater better resembled the ion composition of the seas of the Earth from 4 billion years ago. Cyanide and thiocyanate were common molecules in prebiotic Earth, and especially in primitive oceans, where they could act on the magnetite mechanism synthesis via Fe2+ interaction. In this research, magnetite samples that were synthesized under prebiotic conditions in the presence of cyanide or thiocyanate, (both with and without artificial seawater), showed that, besides magnetite, goethite and ferrihydrite can be produced through different Fe2+-ion interactions. Cyanide apparently acts as a protective agent for magnetite production; however, thiocyanate and seawater 4.0 Gy ions produced goethite and ferrihydrite at different ratios. These results validate that Fe3+ oxides/hydroxides were possibly present in primitive Earth, even under anoxic conditions or in the absence of UV radiation. In addition, the results show that the composition of water in early oceans should not be neglected in prebiotic chemistry experiments, since this composition directly influences mineral formation

Application of Aloe vera microcapsules in cotton nonwovens to obtain biofunctional textile

The microencapsulation of essential oils and its application in textile articles allows the aggregation ofdifferent functionalities to the substrates, imparting them antimicrobial properties, cosmetic effects, UVprotection, application of drugs, among others. Therefore, the coacervation technique allows goodresults using starch to prepare the microcapsules. The objective of this work was the microencapsula-tion of Aloe Vera with cornstarch using the simple coacervation technique in cotton nonwoven fabricusing butane tetracarboxylic acid (BTCA) as a binding agent. Optical and Scanning electron microscopywere performed to understand the morphology of the microcapsules obtained; thermogravimetry, tothe comprehension of the thermal degradation of the microcapsules; mass gain percentage; FTIR wasused to prove the interaction between nonwoven and microcapsule and finally, the CIE WI whiteindex. The micrography allowed the observation of granular morphology, predominantly angular. Thethermogravimetric curves have shown two significative thermal events: dehydration of the oil anddegradation of the starch. The samples presented darker coloration; however, their quality was notcompromised by the finishing. For this reason, the characterizations allowed to infer that the simplecoacervation using this method is a simple process, with good results for the encapsulation of essen-tial oils.Peer ReviewedPostprint (author's final draft