TY - JOUR
T1 - Mechanistic insights into the electrochemical reduction of CO2 to CO on Ni(salphen) complexes
AU - Realista, S.
AU - Costa, Paulo J.
AU - Maia, Luísa
AU - Calhorda, Maria José
AU - Martinho, Paulo N.
N1 - Funding Information:
info:eu-repo/grantAgreement/FCT/6817 - DCRRNI ID/UIDB%2F04046%2F2020/PT#
info:eu-repo/grantAgreement/FCT/6817 - DCRRNI ID/UIDP%2F04046%2F2020/PT#
info:eu-repo/grantAgreement/FCT/6817 - DCRRNI ID/UIDB%2F50006%2F2020/PT#
info:eu-repo/grantAgreement/FCT/6817 - DCRRNI ID/UIDP%2F50006%2F2020/PT#
info:eu-repo/grantAgreement/FCT/3599-PPCDT/PTDC%2FBTA-BTA%2F0935%2F2020/PT#
info:eu-repo/grantAgreement/FCT/6817 - DCRRNI ID/UIDB%2F00100%2F2020/PT#
info:eu-repo/grantAgreement/FCT/6817 - DCRRNI ID/UIDP%2F00100%2F2020/PT#
info:eu-repo/grantAgreement/FCT/Investigador FCT/IF%2F00069%2F2014%2FCP1216%2FCT0006/PT#
info:eu-repo/grantAgreement/FCT/OE/SFRH%2FBSAB%2F135473%2F2017/PT#
info:eu-repo/grantAgreement/FCT/CEEC IND 2017/CEECIND%2F00509%2F2017%2FCP1387%2FCT0029/PT#
info:eu-repo/grantAgreement/FCT/CEEC IND 3ed/2020.02134.CEECIND%2FCP1605%2FCT0002/PT#
info:eu-repo/grantAgreement/FCT/CEEC IND4ed/2021.00381.CEECIND%2FCP1650%2FCT0004/PT#
LA/P/0056/2020.
The NMR spectrometers are part of the National NMR Network (PTNMR) and are partially supported by Infrastructure Project No 022161 (co-financed by FEDER through COMPETE 2020, POCI and PORL and FCT through PIDDAC).
FCT is acknowledged for PTDCQUI-QIN0252_2021 (PNM).
The CARISMA COST action CM1205 is acknowledged. MJC thanks N. A. G. Bandeira for technical assistance. The CATSUS doctoral programme is also acknowledged.
Publisher Copyright:
© 2023 The Royal Society of Chemistry.
PY - 2023/7
Y1 - 2023/7
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85163835892&partnerID=8YFLogxK
U2 - 10.1039/d3qi00424d
DO - 10.1039/d3qi00424d
M3 - Article
SN - 2052-1553
SP - 4175
EP - 4189
JO - Inorganic Chemistry Frontiers
JF - Inorganic Chemistry Frontiers
IS - 14
ER -