Joana A. Silva

Porphyrins as nanoreactors in the carbon dioxide capture and conversion: a review

On account of their unique properties and robust structures, porphyrins are natures favorite catalysts. Porphyrins have attracted the attention of researchers for many decades as a result of their intense colors; but in recent years, interest in these molecules has sharply increased, due to their potential use in solving difficult problems in the fields of medicine and environmental protection. Much attention is currently focused on the development of materials for the capture and conversion of CO2 into value-added products, and porphyrins are proving to be of interest in this area of research. Porphyrins were previously thought to be poorly-absorbant materials, as they are generally planar compounds. However, the development of new, efficient porphyrin-based materials and reliable synthetic routes for porphyrin-based nanoreactors, such as covalent–organic frameworks and metal–organic frameworks, for use as porous materials has helped to overcome the underlying challenges in CO2 reactivity. Porphyrin-based materials that behave as nanoreactors are promising candidates in the capture and conversion of CO2 as a result of the presence of the basic pyrrole structure that contains a macrocyclic cavity and large aromatic rings, which facilitate strong interactions with CO2. This review provides an overview of progress in the area of CO2 capture and conversion using porphyrin-based molecular materials and nanoreactors. These materials have important structural features in terms of surface area, porosity, CO2 uptake and the possibility of the catalytic conversion of CO2 to chemically valuable products.

Studies of Carbon Dioxide Capture on Porous Chitosan Derivative

Chitosan was modified with 4-formyltriphenylamine to obtain a material with better surface morphology and adsorption profile. Surface morphology and Brunauer–Emmett–Teller (BET) analysis has proved that the chitosan derivative presents higher porosity. CO2 adsorption analysis results reveal that the triphenyl amine chitosan derivative shows better adsorption than pure chitosan. The results revealed that this material may open new vistas in environmental and industrial applications for carbon dioxide capture, in order to help to reduce the adverse impact of large emissions of the greenhouse gas is the atmosphere. GRAPHICAL ABSTRACT

Photophysical Characterization and in Vitro Phototoxicity Evaluation of 5,10,15,20-Tetra(quinolin-2-yl)porphyrin as a Potential Sensitizer for Photodynamic Therapy

Photodynamic therapy (PDT) is a selective and minimally invasive therapeutic approach, involving the combination of a light-sensitive compound, called a photosensitizer (PS), visible light and molecular oxygen. The interaction of these per se harmless agents results in the production of reactive species. This triggers a series of cellular events that culminate in the selective destruction of cancer cells, inside which the photosensitizer preferentially accumulates. The search for ideal PDT photosensitizers has been a very active field of research, with a special focus on porphyrins and porphyrin-related macrocycle molecules. The present study describes the photophysical characterization and in vitro phototoxicity evaluation of 5,10,15,20-tetra(quinolin-2-yl)porphyrin (2-TQP) as a potential PDT photosensitizer. Molar absorption coefficients were determined from the corresponding absorption spectrum, the fluorescence quantum yield was calculated using 5,10,15,20-tetraphenylporphyrin (TPP) as a standard and the quantum yield of singlet oxygen generation was determined by direct phosphorescence measurements. Toxicity evaluations (in the presence and absence of irradiation) were performed against HT29 colorectal adenocarcinoma cancer cells. The results from this preliminary study show that the hydrophobic 2-TQP fulfills several critical requirements for a good PDT photosensitizer, namely a high quantum yield of singlet oxygen generation (Φ∆ 0.62), absence of dark toxicity and significant in vitro phototoxicity for concentrations in the micromolar range.

Carbon dioxide capture and conversion by an environmentally friendly chitosan based meso-tetrakis(4-sulfonatophenyl) porphyrin

We have demonstrated the facile, environmentally friendly and sustainable preparation of chitosan based meso-tetrakis(4-sulfonatophenyl)porphyrin (CS-TPPS) for adsorption and catalytic conversion of carbon-dioxide (CO2). The ionic complexation between chitosan (CS) and meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) is confirmed by ultraviolet-visible (UV-vis) and Fourier transform infrared spectroscopy (FTIR). Physical properties, such as crystallinity, thermal stability, surface morphology and porosity were analyzed by X-ray diffraction, thermal analysis, scanning electron microscopy and BET isotherm analysis. CS-TPPS shows adsorption capacity of 0.9mmol CO2/g compared to the adsorption capacity of 0.05mmol CO2/g of pure chitosan and an adsorption capacity of 0.2mmol CO2/g of pure TPPS. It also exhibits higher conversion of CO2 and propylene oxide into cyclic carbonate (66%), compared to pure chitosan (31%). The results are encouraging, and may open new perspectives for the use of biopolymers involving porphyrin based material in environmental and industrial applications.

Synthesis and structural characterization of a new self-assembled disulfide linked meso-tetrakis-porphyrin macromolecular array

The synthesis of a new self-assembled porphyrin macrostructure based on disulfide bonds, is presented. This constitutes a new way to directly connect porphyrins in macromolecular arrays, to complement the usual methods of intermolecular hydrogen bonds and metal coordination bonding.

4-Amino-3,5-di-2-pyridyl-4H-1,2,4-triazole

In the crystal structure of the title compound, C12H10N6, the molecules deviate slightly from planarity. The plane of the central triazole ring makes angles of 6.13 (9) and 3.28 (10)° with the pyridyl ring planes. Intramolecular N—H⋯N interactions form six-membered closed rings. The crystal packing also shows weak C—H⋯π and C—H⋯N interactions.

Bis[(2-quinol­yl)methane­diol-κ2N,O](sulfato-κO)copper(II) dihydrate

In the title compound, [Cu(SO4)(C10H9NO2)2]·2H2O, the CuII ion is chelated by two (2-quinolyl)methanediol ligands and coordinated by a monodentate sulfate ligand in a distorted trigonal–bipyramidal environment, with O atoms occupying the equatorial sites and N atoms in the axial sites. The dihedral angle between the two essentially planar quinoline ring systems is 45.02 (9)°. In the crystal structure, an extensive O—H⋯O hydrogen-bonding network forms layers parallel to the ab plane.

N,N'-Bis-[(E)-(6-methyl-2-pyridyl)-methyl-ene]hexane-1,6-diamine.

The title compound, C20H26N4, is composed of two (6-methyl-2-pyridyl)methylene units linked by a 1,6-diamine hexane chain. The molecule has Ci symmetry with the inversion center situated at the mid-point of the central C—C bond. The alkyl chain has an all-trans conformation, with all the non-H atoms sharing the same plane [maximum deviation 0.004 (3) Å]. The pyridylmethylene groups are also planar [maximum deviation 0.009 (3) Å], making an angle of 53.78 (19)° with the hexane chain plane. In the crystal, the molecules assemble in layers, stacking along the a axis. The stacks are hold together by attractive interactions between π electron systems.

Paal–Knorr synthesis of pyrroles: from conventional to green synthesis

ABSTRACT The pyrrole molecular framework is found in a large number of natural and synthetic compounds of great importance. Since functionalized pyrroles are essential for the progress of many branches of science, its synthesis by simple, efficient and eco-friendly routes are particularly attractive in modern organic and bio-organic chemistry. To this end, a number of synthetic methods have been developed, in which the Paal–Knorr pyrrole synthesis stands out to be the easiest route to synthesize pyrroles. In spite of the efficiency, Paal–Knorr synthesis of pyrroles is considered limited by harsh reaction conditions, such as prolonged heating in acid, which may degrade sensitive functionalities in many potential precursors. Through this route almost all dicarbonyls can be converted to their corresponding heterocycles and therefore it is a synthetically valued process. To address the adverse issues this reaction route has undergone numerous modifications recently and today it can be said that this reaction route is a prominent green route for the synthesis of pyrroles. This review is a tour from the evolution and application of this harsh synthetic route to the eco-friendly greener route developed for the synthesis of pyrroles.

Diaqua­(6-bromo­picolinato-κ2N,O)(nitrato-κ2O,O)copper(II)

In the monomeric title complex, [Cu(C6H3BrNO2)(NO3)(H2O)2], the CuII ion is coordinated by a bidentate 6-bromopicolinate ion, one nitrate ion and two water molecules in a geometry intermediate between five- and six-coordinate. Conventional O—H⋯O hydrogen bonds link the complex molecules, forming layers parallel to the ab plane.