CICECO – Aveiro Institute of Materials

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Inclusion complexes of cucurbit[n]urils (n = 7, 8) with η5 -cyclopentadienyl methyl tricarbonyl molybdenum(II) and their use in epoxidation catalysis

Publication . Neves, Patrícia; Gomes, Ana C.; Monteiro, Rodrigo P.; Santos, Mirela J.; Valente, Anabela A.; D. Lopes, André; Gonçalves, Isabel S.; Pillinger, Martyn

There are very few known examples of supramolecular compounds comprising molybdenum species hosted inside the portals/cavities of cucurbit[n]urils (CBn). In this work, CB7 and CB8 macrocycles have been studied as hosts for the carbonyl complex [CpMo(CO)(3)Me] (1) (Cp = eta(5)-C5H5). Compounds were isolated in the solid state and characterized as genuine 1:1 inclusion complexes (1@CBn) by elemental and thermogravimetric analyses, powder X-ray diffraction, scanning electron microscopy, C-13{H-1} cross-polarization magic-angle spinning NMR, FT-IR, Raman, and diffuse reflectance UV-Vis spectroscopies. The host-guest structures can act as supramolecular precatalysts for olefin epoxidation. Based on the model reaction of cis-cyclooctene with hydroperoxide oxidants (tert-butylhydroperoxide or hydrogen peroxide), the structural features of 1@CBn as well as the operating conditions influence the catalytic process. The metal species in 1@CBn undergo oxidative decarbonylation in situ, giving oxidized metal species that are catalytically active for olefin epoxidation. The type of oxidant and solvent influences the catalytic activity and stability. 1@CB8 was more stable than 1@CB7 with regard to catalyst recycling and reuse. Based on the substrate scope investigation, for relatively large olefins, such as the fatty acid methyl ester methyl oleate, the size of the macrocyclic host may be a determining factor for catalytic activity.

2024-03Journal article

Open access

Synthesis, structure and antileishmanial evaluation of endoperoxide–pyrazole hybrids

Publication . Amado, Patrícia S. M.; Costa, Inês C. C.; Paixão, José A.; Mendes, Ricardo F.; Cortes, Sofia; Cristiano, Maria L.

Leishmaniases are among the most impacting neglected tropical diseases. In attempts to repurpose antimalarial drugs or candidates, it was found that selected 1,2,4-trioxanes, 1,2,4,5-tetraoxanes, and pyrazole-containing chemotypes demonstrated activity against Leishmania parasites. This study reports the synthesis and structure of trioxolane–pyrazole (OZ1, OZ2) and tetraoxane–pyrazole (T1, T2) hybrids obtained from the reaction of 3(5)-aminopyrazole with endoperoxide-containing building blocks. Interestingly, only the endocyclic amine of 3(5)-aminopyrazole was found to act as nucleophile for amide coupling. However, the fate of the reaction was influenced by prototropic tautomerism of the pyrazole heterocycle, yielding 3- and 5-aminopyrazole containing hybrids which were characterized by different techniques, including X-ray crystallography. The compounds were evaluated for in vitro antileishmanial activity against promastigotes of L. tropica and L. infantum, and for cytotoxicity against THP-1 cells. Selected compounds were also evaluated against intramacrophage amastigote forms of L. infantum. Trioxolane–pyrazole hybrids OZ1 and OZ2 exhibited some activity against Leishmania promastigotes, while tetraoxane–pyrazole hybrids proved inactive, most likely due to solubility issues. Eight salt forms, specifically tosylate, mesylate, and hydrochloride salts, were then prepared to improve the solubility of the corresponding peroxide hybrids and were uniformly tested. Biological evaluations in promastigotes showed that the compound OZ1•HCl was the most active against both strains of Leishmania. Such finding was corroborated by the results obtained in assessments of the L. infantum amastigote susceptibility. It is noteworthy that the salt forms of the endoperoxide–pyrazole hybrids displayed a broader spectrum of action, showing activity in both strains of Leishmania. Our preliminary biological findings encourage further optimization of peroxide–pyrazole hybrids to identify a promising antileishmanial lead.

2022-08-24Journal article

Open access

A glance at novel ionanofluids incorporating silk-derived carbon dots

Publication . Duarte, Tiago A. G.; Pereira, Rui F. P.; Medronho, Bruno; Maltseva, Elizaveta S.; Krivoshapkina, Elena F.; Varela-Dopico, Alejandro; Taboada, Pablo; Fu, Lianshe; Ferreira, Rute A. S.; de Zea Bermudez, Verónica

One of the hallmarks of the current efforts in the field of thermal energy is heat transfer enhancement. Ionanofluids (INFs), a combination of nanomaterials and ionic liquids (ILs), are an appealing category of thermal fluids. In this work, we introduce sustainable INFs composed of carbon dots derived from Bombyx mori silk fibroin (SF) dispersed in a mixture of 1-butyl-3-methylimidazolium chloride (IL1) and 1-(4-sulfobutyl)-3-methylimidazolium triflate (IL2). The syntheses were performed at mild conditions, with reaction times of 3, 4, and 5 h, and without purification steps. The INFs display room-temperature emission in the visible spectral range with quantum yield values up to 0.09 and are essentially viscous fluids (G '' > G '). A marked shear thinning behavior is observed at high shear rates, particularly for the systems SFIL1IL2-3h and SFIL1IL2-4h. The INFs demonstrate relatively high heat capacity and thermal conductivity values in comparison to state-of-the-art INFs. Under suitable illumination conditions, the INFs can convert light into heat in an efficient manner, with photothermal conversion efficiencies of up to 28%, similar to other reported INFs. SFIL1IL2-5h exhibits remarkable stability over time within the range of working temperatures. This work paves the way for the development of new thermal fluids for enhanced heat transfer technologies using sustainable synthesis routes and natural raw precursor materials.

2024Journal article

Restricted access

Anti-obesogenic effects of plant natural products: A focus on Korean traditional foods

Publication . Das, Gitishree; Jiménez Ortega, Luis Alfonso; Gonçalves, Sandra; Heredia, J. Basilio; Pereira, Maria de Lourdes Gomes; Shin, Han-Seung; Romano, Anabela; Jayanta Kumar Patra

Natural products from food can play an important role in obesity management. Korean traditional food (KTF), characterized by a high inclusion of fresh or prepared vegetables, a reasonable contribution of fish, pulses, and with very little amount of meat, is one of the most recognized cuisines for its nutritional quality, diversity, and flavor. The traditional Korean food contains relevant phytochemicals and probiotic microorganisms with anticancer, anti-mutagenic, antioxidant, and anti-obesogenic properties. Scope: Obesity is a chronic degenerative pathology which causes adverse effects on health, low quality of life, and social costs. The use of fermentation as a conservation/preparation method increases the functional value of KTF, conferring new medicinal properties such as anti-obesogenic. Key findings and conclusions: This review article summarizes data about the anti-obesogenic properties of phytochemicals and KTF. Reviewed results indicated that several phytochemicals present in KTF (e.g., flavonoids, saponins, terpenes) exerted anti-obesogenic effects due to their antioxidant, anti-inflammatory, inhibition of enzymes related to lipid and carbohydrate metabolism, inflection of lipid homeostasis, thermogenic, life cycle of adipocyte, and appetite suppression. Besides, both in vivo and medical research have showed that fermented products extensively included in KTF have a positive effect on the reduction of obesity through different mechanisms particularly by altering human metabolism and affecting gut microbiota. Some molecular mechanisms among these anti-obesogenic agents, are referred in research, focused on the search for phytochemicals that can intervene with leptin sensitizers, GLP1/glucagon dual agonists, GIP/GLP1/glucagon tri-agonists, amylin/calcitonin dual agonists, Y2R agonists, GIP/GLP1 dual agonists, drugs targeting the ghrelin pathway, and GLP1R agonists. Overall, the current review highlights the anti-obesogenic impact of KTF in accordance with the low rate of obesity in the Korean population.

2024-06Journal article

Restricted access

Host-guest complexes of cucurbit[8]uril and [(η5-C5H4R)Mo(CO)3CH3] (R = H, CO2CH3) for controlled release of carbon monoxide

Publication . Gomes, Ana C.; Monteiro, Rodrigo P.; Calhau, Isabel B.; D. Lopes, André; Gonçalves, Isabel S.; Pillinger, Martyn

The monosubstituted cyclopentadienyl half-sandwich molybdenum(II) tricarbonyl complex [(eta 5-C5H4CO2CH3) Mo(CO)3CH3] (1) and its 1:1 inclusion compound with cucurbit[8]uril (1@CB8) have been prepared and characterised by elemental and thermogravimetric analyses, powder X-ray diffraction, diffuse reflectance UV-vis, solid-state 13C{1H} MAS NMR, FT-IR, and Raman spectroscopies. The CO-releasing behaviours of 1, 1@CB8 and, for comparison, [(eta 5-C5H5)Mo(CO)3CH3] (2) and its 1:1 inclusion complex with CB8, were assessed using a deoxymyoglobin-carbonmonoxymyglobin assay. For assays performed in the dark at 37 degrees C, complex 1 undergoes thermally assisted spontaneous CO release, with ca. 0.5 equivalents of CO being released after 6 h. The half-life (t1/2) of 325 min identifies 1 as a slow releaser when compared to complex 2 bearing the unsubstituted cyclopentadienyl ligand (t1/2 = 25 min). CO release from 1 was promoted by exposure to UV light (t1/2 = 85 min), establishing the complex as a photochemically activated CO-releasing molecule (photoCORM). For 1@CB8, t1/2 for photo-assisted CO release increased to ca. 7 h, and for 2@CB8 the dark-release t1/2 increased to 165 min, showing that molecular acceptors like cucurbiturils can be used effectively as second-sphere ligands to modulate the CO release profile of CORMs.

2024-10Journal article

Open access