In the ~150 years comprised between the discovery of yttrium (1794) and promethium (1947), the rare earth metals were an incomplete chapter and a stone in the shoe of the periodic classification of the chemical elements. This group of 17 elements with remarkable chemical similarity raised confusion on many brilliant scientists, including Mendeleev, and led to the consolidation of many theories in Chemistry, from atomic spectroscopy to quantum theory. Nowadays we know that the special properties of these elements arise from filling 4f orbitals, which results in unique spectroscopic, magnetic and catalytic behavior. Such properties make rare earths essential elements on optical devices, lasers, telecommunications and magnetic materials for sustainable energy. The importance of rare earths far exceeds the science and technology domains, reaching the same level of other strategic materials for energy and defense. Hence, this work presents a brief discussion about the historical path of the rare earth elements in the Periodic Table and about the exploration of these resources in Brazil, detailing some of the extractive activities since the 19th century and some perspectives for future activities concerning this group of elements in Brazil.

Lanthanoid organic frameworks (LOFs) stand out as an important class of functional materials. The possibility to employ a great range of metals and ligands lead to the formation of varied and highly porous structures, with diverse applications. The presence of lanthanoid ions favours the improvement of the optical, magnetic and redox properties of MOFs. This review aims to demonstrate the state of the art of LOFs, emphasizing the chemical properties of trivalent lanthanoid ions and the carboxylic based-ligands used in their construction, as well as the main characterization methods and outstanding applications as gas storage, permanent magnets, catalysis, luminescence, drug delivery and so on.

Light and rare earths (RE) have a long lived relationship that dates from the discoveries of these elements in the nineteenth century. Since then, the increasing comprehension of their spectroscopic properties conducted to a wide and alluring literature about light absorption and emission by this particular and fascinating group. For more than 50 years, RE-containing solid-state optical materials have undoubtfully been an important subject for the development of more efficient lighting, visualization, communication and health everyday applications. Therefore, this review introduces the spectroscopic properties of rare earth materials and their applications, with a brief discussion of the main mechanisms of light absorption and emission from a 4f elements inorganic physical chemistry perspective. Special attention is devoted to the use of these elements in systems concerning photoprotection and to the fundamentals of visible light generation for lighting and visualization.

<p>Catalytic combustion of soot was performed over ZnO:CeO₂ catalysts obtained via a non‑alkoxide sol-gel route. Different kinetics parameters were calculated through thermal analyses, thus, enabling the correlation between the experimental data and the decomposition mechanisms probably associated with the soot decomposition in each case.</p>

AbstractThe oil extracted by cold pressing unroasted coffee beans, known as green coffee oil, has been widely used for cosmetic purposes. The objective of this work was to prepare and characterize microcapsules containing green coffee oil and to verify its antioxidant activity under the effect of light, heat and oxygen. The encapsulating material was arabic gum and the microcapsules were obtained by spray drying an oil-in-water emulsion containing green coffee oil. The characterization of the microcapsules was performed by laser diffraction, scanning electron microscopy, differential scanning calorimetry and the antioxidant activity. The antioxidant activity was determined by a modified active oxygen method with light irradiation, heating and oxygen flux. The microparticles were effectively produced by the proposed spray drying method, which resulted in green coffee oil loads of 10 and 30%. The morphological evaluation of microcapsules showed spherical shape with smooth and non-porous surfaces, demonstrating the adequacy of arabic gum as encapsulating material. Calorimetric analysis of individual components and microcapsules with 10 and 30% green coffee oil showed diminished degradation temperatures and enthalpy, suggesting a possible interaction between arabic gum and green coffee oil. The antioxidant activities for pure green coffee oil and its microcapsules with loads of 10 and 30% showed high activity when compared to the reference antioxidant alfa-tocopherol. Microcapsules containing 10 and 30% of oil showed 7-fold and 3-fold increase in antioxidant activity when compared to pure green coffee oil. The new method for antioxidant activity determination proposed here, which applies heat, light and oxygen simultaneously, suggests a high improvement in encapsulated green coffee oil when compared to this active alone. The results showed herein indicate a promising industrial application of this microencapsulated green coffee oil.

<p>Liquid phase synthesis techniques are commonly preferred for the preparation of nanosized inorganic solids due to several advantages over other methodologies, such as low energy consumption, safety, possibility of reactant recovery and, mainly, the homogeneity of the precursors and control of particle sizes and morphologies through bottom-up approaches. In this regard, Colloidal Chemistry plays a key role in the controlled production of different classes of nanoparticles, thus being a subject of growing interest in several fields of Materials, Inorganic, and Physical-Chemistry. Therefore, this article sought to present an introductory outline of Colloidal Chemistry, with a focus on the preparation of inorganic nanoparticles. Given the broadness of this subject, special attention was devoted to nanoparticles based on Rare Earth compounds, due to their current importance in several fields. Therefore, the work presents the principles involved in the most commonly applied methodologies for the liquid phase synthesis of nanoparticles, such as coprecipitations and hydro/solvothermal techniques, as well as precipitations into nanoreactors based on reverse microemulsions, with a brief survey of the main advances in these fields in recent years.</p>

This contribution introduces a brief discussion about the properties and applications of the rare earth elements, with a focus on their current status in Brazil. The general chemical properties, main applications and historical background of the chemistry of these elements are presented, and special attention is devoted to the development of the exploitation and both academic and industrial activities involving rare earths in Brazil. A discussion of the current world scenario ensues and some perspectives regarding the prospection, market and government policy concerning the rare earth elements in Brazil are given.

CeO2 and mixed CeO2-ZrO2 nanopowders were synthesized and efficiently deposited onto cordierite substrates, with the evaluation of their morphologic and structural properties through XRD, SEM, and FTIR. The modified substrates were employed as outer heterogeneous catalysts for reducing the soot originated from the diesel and diesel/biodiesel blends incomplete combustion. Their activity was evaluated in a diesel stationary motor, and a comparative analysis of the soot emission was carried out through diffuse reflectance spectroscopy. The analyses have shown that the catalyst-impregnated cordierite samples are very efficient for soot oxidation, being capable of reducing the soot emission in more than 60%.

Filmes de aluminato de zinco dopados com európio (ZnAl2O4:Eu3+) foram preparados pelo método sol-gel usando precursores não-alcóxidos em meio etanólico através da técnica de dip-coating. Os espectros de fotoluminescência do filme aquecido a 500 ºC apresentaram bandas de excitação em 270 e 393 nm e bandas de emissão em 578, 590, 612, 650 e 698 nm, atribuídas às transições 5D0 → 7F J (J = 0, 1, 2, 3, 4). Os filmes mostraram-se transparentes acima de 320 nm.

Europium-doped zinc aluminate (ZnAl2O4:Eu3+) films were prepared by the dip-coating technique using a non-alkoxide precursor sol-gel method in ethanolic medium. Photoluminescence spectra displayed the main excitation bands at 270 and 393 nm. The emission spectra of the film heated at 500 ºC displayed bands at 578, 590, 612, 650 and 698 nm, assigned to the 5D0 → 7F J (J = 0, 1, 2, 3, 4) transitions. The films are transparent above 320 nm.

Neste trabalho descrevemos a síntese de beta-dicetonatos de Tb3+ e o aumento de sua solubilidade em água através da formação de compostos de inclusão em alfa-ciclodextrina (alfa-CD). Os complexos [Tb(ppa)3(H2O)2] e [Tb(ppa)3(phen)] (ppa=3-fenil-2,4-pentanodiona; phen = fenantrolina) foram sintetizados, caracterizados e a seguir incluídos em alfa-ciclodextrina. A inclusão foi confirmada por ¹H NMR e a estequiometria de associação determinada pelo método de Job. Nos espectros de excitação, os comprimentos de onda dos máximos de intensidade dos compostos de inclusão em solução aquosa [Tb(ppa)3(H2O)2]:a -CD e [Tb(ppa)3(phen)]:alfa-CD apresentaram-se deslocados em 15 e 60 nm, respectivamente, com relação aos comprimentos de onda dos máximos dos complexos não incluídos. Nos espectros de emissão, as bandas características do Tb3+ foram observadas mesmo após a inclusão dos compostos em alfa-CD.

In this work we describe how the inclusion of Tb3+ beta-diketonate chelates into the hydrophobic cavity of alpha-cyclodextrin enhances the solubility of the complexes in aqueous medium and leads to changes in their photophysical properties. To this end, the complexes [Tb(ppa)3(H2O)2] and [Tb(ppa)3(phen)] (ppa=3-phenyl-2,4-pentanedione; phen = phenantroline) were synthesized and characterized, and they were then included into alpha-cyclodextrin pockets. This inclusion was confirmed by ¹H NMR spectroscopy and the stoichiometry was determined by means of the Job method. In the excitation spectra, the maximum intensity wavelength of the inclusion compounds [Tb(ppa)3(H2O)2]: alpha-CD and [Tb(ppa)3(phen)]:alpha-CD were displaced 15 and 60 nm respectively when compared with the non-CD starting complexes. The typical Tb3+ emission bands were maintained after inclusion of the complexes into alpha-CD and their subsequent solubilization in aqueous medium.

A terapia fotodinâmica (TFD) está baseada na administração e no acúmulo de fotossensibilizador, por exemplo, de tipo porfirina ou clorina, em tecidos doentes. As clorinas apresentam propriedades fotofísicas semelhantes àquelas das porfirinas, mas com intensificação e deslocamento das bandas Q, o que faz com que sejam bons candidatos para TFD. Neste trabalho relata-se a síntese da 5,10,15-tris(pentafluorofenil)-20-(4-piridil)porfirina, (2), e das clorinas isômeras 4, (5,10,20-tris(pentafluorofenil)-15-(4-piridil)-tetra-hidro-1H- N-metil-pirrolo[3,4-b]porfirina e 5, (5,10,15-tris(pentafluorofenil)-20-(4-piridil)-tetra-hidro-1H- N-metil-pirrolo[3,4-b]porfirina, obtidas a partir de 2, por reação de cicloadição 1,3-dipolar com um ileto azometínico, e respectivas caracterizações estruturais por UV-Vis, RMN e EM-FAB. Foram avaliadas as propriedades fotofísicas, fotoquímicas e fotodegradativas para a nova clorina 4, obtida com melhor rendimento que o seu isômero 5. O rendimento quântico de fotodegradação (fiFd, mol Einstein-1) foi de 0,047±0,014. Foram ainda realizados testes com ácido úrico para demonstrar a capacidade do fotossensibilizador na produção de ¹O2. Os resultados mostraram que a nova clorina 4 pode ser considerada como um bom fotossensibilizador para TFD.

Photodynamic therapy (PDT) is based on the accumulation of a photosensitizer, such as a porphyrin or a chlorin, in a malignant tissue after its administration. Chlorins exhibit photophysical properties similar to those of the porphyrin macrocycles, but with intensified and red-shifted Q bands, making chlorin-containing systems even better candidates for PDT. In this contribution, we report the synthesis of 5,10,15-tris(pentafluorophenyl)-20-(4-pyridyl)porphyrin, (2) and its transformation to the novel chlorin derivatives 4, (5,10,20-tris(pentafluorophenyl)-15-(4-pyridyl)-tetrahydro-1H- N-methyl-pyrrolo [3,4-b]porphyrin and 5, (5,10,15-tris(pentafluorophenyl)-20-(4-pyridyl)-tetrahydro-1H- N-methyl-pyrrolo[3,4-b]porphyrin) by 1,3-dipolar cycloaddition with an azomethine ylide. The new products have been characterized by UV-Vis, ¹H NMR and FAB-MS. The photophysics, photochemical and photobleaching properties of chlorin 4 have been evaluated. Its quantum yield of photobleaching (phiPb, mol Einstein-1) was 0.047±0.014. In order to demonstrate the production of ¹O2 when 4 is used as a photosensitizer, uric acid tests have been carried out. The results indicate that chlorin 4 can be considered a promising photosensitizer in PDT.

As hidroxinitrofenilporfirinas, 5,10,15,20-tetrakis(2-hidroxi-5-nitrofenil)porfirina e 5-mono(carboxifenil)-10,15,20-tris(2-hidroxi-5-nitrofenil)porfirina , estudadas neste trabalho, foram preparadas pelo método de Adler e caracterizadas por ¹H RMN e por espectroscopia de absorção e emissão na região espectral visível. A formação de ¹O2 foi constatada através do teste do ácido úrico (AU), o qual consiste na observação do decréscimo na absorbância da banda do AU em 293 nm, após irradiação da solução, com laser, contendo o fotossenssibilizador e o AU. Os resultado obtidos indicaram que as hidroxinitrofenilporfirinas podem ser consideradas potenciais fotossensibilizadores para terapia fotodinâmica.

The hydroxynitrophenylporphyrins, 5,10,15,20-tetrakis(2-hydroxy-5-nitrophenyl)porphyrin and 5-mono(carboxyphenyl)-10,15,20-tris(2-hydroxy-5-nitrophenyl)porphyrin described in this work were prepared through Adler's method. These compounds were characterized by ¹H NMR and light absorption and emission spectroscopy in the visible region. In order to demonstrate the involvement of ¹O2 production, the uric (UA) acid test was carried out, which considers the decrease in the absorbance of UA at 293 nm following laser light irradiation of a solution containing UA and a photosensitizer. The results obtained demonstrate that these hydroxynitrophenylporphyrins can be considered as promising photosensitizers in PDT.

This article focuses on the development of Inorganic Chemistry in Brazil, including historical perspectives, scientific production (WEB-ISI data), international cooperation, teaching, literature and human resources, with particular emphasis on the last 25 years.

O complexo de Pt(II) [Pt(SPh)2(dppen)] (4) , (dppen, Ph2PCH=CHPPh2), estável, foi obtido de [PtCl(SPh)2(SnPh3)cod] (1) (cod = 1,5-ciclooctadieno), por eliminação redutiva de SnClPh3 e substituição do ligante cod pela difosfina, porém em baixo rendimento. Contudo, quando [Pt(SPh)2cod] (3) foi utilizado como material de partida, 4 foi obtido em rendimento de 80%. A viabilidade dessas reações foi sugerida por estudos de TG dos materiais de partida. O complexo 4 foi caracterizado por espectroscopia de RMN multinuclear (195Pt, 31 P, ¹H e 13C), IV e análise elementar. A estrutura molecular de 4, resolvida por um estudo de difração de raios X, exibe geometria quadrática plana ligeiramente distorcida e distâncias de ligação C=C e Pt-P pequenas, o que foi interpretado em termos de uma interação p entre a ligação dupla e a ligação metal-ligante, de acordo com dados descritos na literatura.

The stable Pt(II) complex [Pt(SPh)2(dppen) (4), (dppen, Ph2PCH=CHPPh2) was obtained from [PtCl(SPh)2(SnPh3)cod] (1) (cod = 1,5-cyclooctadiene) by reductive elimination reaction of SnClPh3 and substitution of the cod ligand by the diphosphine, albeit in low yields. Yields of 80% were obtained when [Pt(SPh)2cod] (3) was used as the starting material instead. The viability of these reactions was suggested by a TG study, performed on the starting materials. Complex 4 was characterized by multinuclear NMR (195Pt, 31P, ¹H and 13C) and IR spectroscopies and elemental analysis. The molecular structure, solved by an X-ray diffraction study, exhibted a slightly distorted square-planar geometry and short C=C and Pt-P bond distances which were interpreted in terms of a p interaction between the double bond and the metal-ligand bond, as observed for other diphosphine compounds described previously.

Silica gel was functionalised with chloropropyl groups through the sol-gel process and then a beta-diketone was incorporated into the support. Afterwards, Eu3+ ion and its chelates of 1,10-phenantroline (phen) and 2,2'-bipyridine (bpy), red phosphors, were supported on such silica. Luminescence studies of Eu3+ bound to this new material have shown that there is an increase in the intensity of the emission when the ion is isolated by ligands in the silica matrix. The energy transfer from the ligands phen and bpy to Eu3+ ion was observed in the excitation spectra, which present new bands ascribed to the ligands and/or complex. The Eu3+-functionalised silica was characterised by TGA and FTIR. TGA analysis showed that there is a large loss of mass around 300 °C, which is ascribed to the organic part of the material. The FTIR spectra presented the vibration modes for Si-C and -CH2-. The luminescent properties of the ions surrounding the Eu3+ ion were studied. The decay curve displayed a bi-exponential behaviour, indicating that there is more than one site of Eu3+ on the surface of the silica.