Tricarbonyl-Pyrazine-Molybdenum(0) Metal-Organic Frameworks for the Storage and Delivery of Biologically Active Carbon Monoxide

abstract

Metal-organic frameworks (MOFs) have high poten-tial as nanoplatforms for the storage and delivery of therapeutic gasotransmitters or gas-releasing molecules. The aim of the present study was to open an investigation into the viability of tricarbonyl-pyrazine-molybdenum (0) MOFs as carbon monoxide-releasing materials (CORMAs). A previous investigation found that the reaction of Mo(CO)6 with excess pyrazine (pyz) in a sealed ampoule gave a mixture comprising a major triclinic phase with pyz-occupied hexagonal channels, formulated as fac-Mo(CO)3(pyz)3/2 center dot 1/2pyz (Mo-hex), and a minor dense cubic phase, formulated as fac- Mo(CO)3(pyz)3/2 (Mo-cub). In the present work, an open reflux method in toluene has been optimized for the large-scale synthesis of the pure Mo-cub phase. The crystalline solids Mo-hex and Mo-cub were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), FT-IR and FT-Raman spectroscopies, and 13C{1H} cross-polarization (CP) magic-angle spinning (MAS) NMR spectroscopy. The release of CO from the MOFs was studied by the deoxy-myoglobin (deoxy-Mb)/carbonmonoxy-myoglobin (MbCO) UV-vis assay. Mo-hex and Mo-cub release CO upon contact with a physiological buffer in the dark, delivering 0.35 and 0.22 equiv (based on Mo), respectively, after 24 h, with half-lives of 3-4 h. Both materials display high photostability such that the CO-releasing kinetics is not affected by irradiation of the materials with UV light. These materials are attractive as potential CORMAs due to the slow release of a high CO payload. In the solid-state and under open air, Mo-cub underwent almost complete decarbonylation over a period of 4 days, corresponding to a theoretical CO release of 10 mmol per gram of material.

keywords

CO-RELEASING MOLECULE; VIBRATIONAL-SPECTRA; INFRARED-SPECTRA; PYRAZINE; NANOPARTICLES; CARRIERS; STATE; IRON; ENCAPSULATION; DERIVATIVES

subject category

Materials Science

authors

Silva, AF; Calhau, IB; Gomes, AC; Valente, AA; Gonçalves, IS; Pillinger, M

Groups

G1 - Porous Materials and Nanosystems
G4 - Renewable Materials and Circular Economy

Projects

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

Sistemas ativados por estímulos para a terapia com monóxido de carbono (SASCOT)

Conversao catalitica de olefinas derivadas da biomassa (BiOle_AcidOxCat)

Rede Nacional de Ressonância Magnética Nuclear (PTNMR)

acknowledgements

We acknowledge funding provided within the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, the CENTRO 2020 Regional Operational Programme (project CENTRO-01-0145-FEDER-028031 and PTDC/QUI-QOR/28031/2017) , and COMPETE 2020 Operational Thematic Program for Competitiveness and Internationalization (project POCI-01-0145-FEDER-030075), financed by national funds through the FCT (Fundacao para a Ciencia e a Tecnologia)/MEC (Ministerio da Educacao e Ciencia) (PIDDAC) and, when applicable, co-financed by the European Union through the European Regional Development Fund (ERDF) under the Portugal 2020 Partnership Agreement. The NMR spectrometers are part of the National NMR Network (PTNMR) and are partially supported by Infrastructure project no. 022161 (co-financed by ERDF through COMPETE 2020, POCI and PORL, and FCT through PIDDAC) . I.B.C. is grateful to the FCT for a PhD studentship (2021.05953.BD). A.C.G. thanks the FCT/MCTES for funding through the Individual Call to Scientific Employment Stimulus (CEECIND/02128/2017).