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Research Project
Prodrugs in Combination with Nanocarriers for Controlled Delivery of Carbon Monoxide
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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.
Host−guest complexes of cyclopentadienyl iron dicarbonyl (CpFe(CO)2) CO-releasing molecules with Cucurbit[7]uril
Publication . Monteiro, Rodrigo P.; Calhau, Isabel B.; Gomes, Ana C.; Mendes, Ricardo F.; Paz, Filipe A. Almeida; D. Lopes, André; Silva, José Paulo da; Romão, Carlos C.; Gonçalves, Isabel S.; Pillinger, Martyn
Iron(II) cyclopentadienyl carbonyl complexes are promising as CO-releasing molecules (CORMs) for therapeutic applications. In common with other metallodrugs, the practical application of Fe-CORMs may require their conjugation with biocompatible carriers to improve their bioavailability and protect them from premature degradation. Here, we show that the CO-releasing properties of the complexes [CpFe(CO)2Cl] (1) and [CpFe(CO)2CH2CONH2] (2) are retained when noncovalently encapsulated within cucurbit[7]uril (CB7), a well-established drug-enhancing excipient. The inclusion compounds were characterized in the solid-state by single-crystal and powder XRD, ATR-IR spectroscopy, Raman spectroscopy, TGA, and 13C{1H} CP MAS NMR. In the crystal structure of 2@CB7, there are two crystallographically independent [2@CB7] binary complexes that differ in the orientation of the guest molecules inside the CB cavity. High-resolution ESI-MS and 1H NMR studies verified the formation and stability of 1:1 2@CB7 inclusion complexes in an aqueous solution. In a physiological buffer, complex 2 is stable in the dark, but releases ca. 1.4 equiv of CO when irradiated with low-power cold white light, with a half-life (t 1/2) of 19.2 +/- 1.9 min. The photodecarbonylation behavior of the complexes is largely maintained in the inclusion compounds, with t 1/2 of 10.0 +/- 0.6 and 21.1 +/- 1.9 min for encapsulated 1 and 2.
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
POR_CENTRO
Funding Award Number
2020.04758.BD