Cláudia T. Arranja

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.

A new nonconjugated naphthalene derivative of meso-tetra-(3-hydroxy)-phenyl-porphyrin as a potential sensitizer for photodynamic therapy.

A new 5,10,15,20‐tetra‐(phenoxy‐3‐carbonyl‐1‐amino‐naphthyl)‐porphyrin was prepared by an isocyanate condensation reaction and its photophysical properties fully evaluated, both in terms of photostability and singlet oxygen production. It shows considerably enhanced photostability when compared with the parent 5,10,15,20‐tetra‐(3‐hydroxy‐phenyl)‐porphyrin, with the photodegradation quantum yields for T(NAF)PP and T(OH)PP being 4.65 × 10−4 and 5.19 × 10−3, respectively. Its photodynamic effect in human carcinoma HT‐29 cells was evaluated. The new porphyrin showed good properties as a sensitizer in photodynamic therapy with an in vitro cytotoxicity IC50 value of 6.80 μg mL−1 for a 24 h incubation. In addition to the potential of this compound, the synthetic route used provides possibilities of extension to a wide range of new sensitizers.

Cycloaddition of CO2 to epoxides using di-nuclear transition metal complexes as catalysts

Studies on the reaction and conversion of CO2 to valuable products have made much progress in recent years, and the search for efficient catalysts is also expanding. Cycloaddition of CO2 to epoxides was carried out selectively using di-nuclear CuII, CoII and NiII complexes (C1, C2 and C3, respectively) as catalysts. The complexes were synthesized in good yield and characterized by various physical and spectroscopic methods. In all complexes the ligand L acted as a bidentate NO donor favouring distorted octahedral, tetrahedral or square planar geometry for C1, C2 and C3, respectively. Complex C2 in the presence of n-Bu4NI as a cocatalyst showed the highest activity among the reported complexes in the cycloaddition reaction.

Chemically modified amino porphyrin/TiO2 for the degradation of Acid Black 1 under day light illumination

In this paper, for the first time, chemically modified 5,10,15,20-meso-tetra-(para-amino)-phenyl-porphyrin/TiO2 (TPAPP/TiO2) was prepared and used for the degradation of an azo dye Acid Black 1 (AB 1) under direct sunlight. Initially, TiO2 was prepared by sol-gel method. Before making a TPAPP/TiO2 composite, the surface modification of TiO2 was carried out with glycidoxypropyltrimethoxy silane (GPTMS) which acts as a coupling agent. This is an epoxy terminated silane and could easily bond to the amino group of TPAPP through epoxy cleavage. The formation of TPAPP/TiO2 was confirmed by different characterization techniques such as FT-IR, XRD, SEM and DRS. The photocatalytic activity of TiO2 was highly influenced by TPAPP. A mechanism was proposed for AB 1 degradation by TPAPP/TiO2 under sun light.

Ethyl 3,5-dimethyl-1H-pyrrole-2-carboxyl-ate.

In the title compound, C9H13NO2, there are two independent molecules per asymmetric unit. The molecules are very similar and almost planar, with the ethoxycarbonyl group anti to the pyrrole N atom. The two independent molecules are joined into dimeric units by strong hydrogen bonds between NH groups and carbonyl O atoms.

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.

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.

Synthesis, physicochemical and optical properties of bis-thiosemicarbazone functionalized graphene oxide

Fluorescent materials are important for low-cost opto-electronic and biomedical sensor devices. In this study we present the synthesis and characterization of graphene modified with bis-thiosemicarbazone (BTS). This new material was characterized using Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible (UV-Vis) and Raman spectroscopy techniques. Further evaluation by X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and atomic-force microscopy (AFM) allowed us to fully characterize the morphology of the fabricated material. The average height of the BTSGO sheet is around 10nm. Optical properties of BTSGO evaluated by photoluminescence (PL) spectroscopy showed red shift at different excitation wavelength compared to graphene oxide or bisthiosemicarbazide alone. These results strongly suggest that BTSGO material could find potential applications in graphene based optoelectronic devices.

On the performance of hybrid functionals for nonlinear optical properties and electronic excitations in chiral molecular crystals: the case of butterfly-shaped dicinnamalacetone

Purely organic chiral molecular assemblies in the solid state hold great potential for non-linear optical applications. Herein, a newly synthesised molecular system is reported, namely, dicinnamalacetone, an otherwise planar molecule that crystallises in a disordered non-centrosymmetric form with four different conformations having an overall predominance of a particular helicity. A combined experimental and theoretical approach, including single-crystal X-ray diffraction, Kurtz-Perry and ab initio methods, is employed to characterise the system and benchmark the performance of hybrid functionals for the prediction of non-linear optical properties and electronic excitations. Comparison of experiment and theory points to a particular set of hybrid functionals that provides an optimal description of this molecular system.

A nonconjugated naphthalene derivative of meso-tetra-(3-hydroxy)-phenyl-porphyrin as a sensitizer for photodynamic therapy

Photodynamic Therapy (PDT) is a clinical procedure that is showing promising results in the treatment of certain types of cancer, including melanomas, oesophageal and retinal cancers [1-4]. The search for molecules suitable for use in PDT is a field of continuing interest. These molecules need to possess certain characteristics, including high affinity for tumour tissues and intense absorption in a region where biological tissues are relatively transparent. Porphyrin derivatives have become prime targets as sensitizers with potential to become good PDT agents, and have already been in use for over a decade in clinical PDT (ex: Foscan®). We report the synthesis and characterization of a meso-tetra-(3-hydroxy)-phenyl-porphyrin (T(OH)PP) derivative to which a naphthyl isocyanate group was attached, giving the meso-tetra-(phenoxy-3-carbonyl-1-amino-naphthyl)-porphyrin (T(NAF)PP (Figure ​(Figure11). Figure 1 The synthesized compound showed considerably enhanced photostability compared with the parent T(OH)PP (photodegradation quantum yield 4.65 × 10-4). The photosensitizer triplet state is normally considered to be essential for PDT, and to lead to the formation of cytotoxic oxygen species [5,6]. The lifetimes and quantum yields of the triplet state of T(NAF)PP were evaluated and presented typical values for this type of compounds. The quenching rate constant by molecular oxygen and singlet oxygen yield were also determined. The photodynamic effect in human carcinoma HT-29 cells was evaluated, and this novel porphyrin showed good properties as a sensitizer in photodynamic therapy with an in vitro cytotoxicity IC50 value of 6.80 μg mL-1 for 24 h incubation.