Ni Oxidation State and Ligand Saturation Impact on the Capability of Octaazamacrocyclic Complexes to Bind and Reduce CO2

• Published in: Molecules (Basel, Switzerland) Vol. 26; no. 14; p. 4139
• Main Authors: Vénosová, Barbora, Jelemenská, Ingrid, Kožíšek, Jozef, Rapta, Peter, Zalibera, Michal, Novotný, Michal, Arion, Vladimir B., Bučinský, Lukáš
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 07-07-2021; MDPI
• Subjects: Affinity; Carbon dioxide; CO2 catalysis; CO2 fixation; CO2 reduction; Covalent bonds; DFT; domain averaged fermi holes; Energy; Geometry; Ligands; nickel complexes; Oxidation; Population studies; Quantum theory
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules26144139

Two 15-membered octaazamacrocyclic nickel(II) complexes are investigated by theoretical methods to shed light on their affinity forwards binding and reducing CO2. In the first complex 1[NiIIL]0, the octaazamacrocyclic ligand is grossly unsaturated (π-conjugated), while in the second 1[NiIILH]2+ one, the macrocycle is saturated with hydrogens. One and two-electron reductions are described using Mulliken population analysis, quantum theory of atoms in molecules, localized orbitals, and domain averaged fermi holes, including the characterization of the Ni-CCO2 bond and the oxidation state of the central Ni atom. It was found that in the [NiLH] complex, the central atom is reduced to Ni0 and/or NiI and is thus able to bind CO2 via a single σ bond. In addition, the two-electron reduced 3[NiL]2− species also shows an affinity forwards CO2.