Towards controlled electrosynthesis of MOF films for biorelevant molecule sensing

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Mechanistic insights into the electrochemical reduction of CO2 to CO on Ni(salphen) complexes

Publication . Realista, S.; Costa, Paulo J.; Maia, Luísa; Calhorda, Maria José; Martinho, Paulo N.; LAQV@REQUIMTE; DQ - Departamento de Química; RSC - Royal Society of Chemistry

Cyclic voltammetry and bulk electrolysis showed that [Ni(ii)(salphen)] [1], [Ni(ii)(tBu-salphen)] [2], and a binuclear Ni(ii) compound combining salphen and tBu-salphen [3] react with CO2 to yield a metal-carbonyl species that is stable under an oxygen free atmosphere. Upon exposure to air, a stoichiometric amount of CO is released (detected by gas chromatography) and protonation regenerates the initial complex. To shed light on the mechanism of CO2 reduction and O2-dependent CO release by [1], UV-vis, EPR and SEC-IR spectroscopy studies complemented with DFT calculations were performed. It is proposed that the mono reduced [Ni(i)(salphen)]−, 2[1]−, formed a CO2 complex, 2[1(CO2)]−, which was then further reduced to 3[1(CO2)]2−. After addition of two protons, the coordinated CO2 was reduced to CO and released, regenerating 1[1]. Alternatively, 2[1(CO2)]− is protonated and then reduced to the same intermediate as before, continuing the same way. In the second cycle, the CO released competed with CO2 and coordinated to 2[1]− much more strongly, thereby deactivating the system. The new 2[1(CO)]− was reduced to 3[1(CO)]2− which was identified by comparison of experimental spectroscopic (UV-vis, EPR, SEC-IR) data with DFT calculated parameters.

2023-07Artigo científico

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Fundação para a Ciência e a Tecnologia

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CEEC IND 3ed

Número da atribuição

2020.02134.CEECIND/CP1605/CT0002