Unveiling the atomistic and electronic structure of Ni^II-NO adduct in a MOF-based catalyst by EPR spectroscopy and quantum chemical modelling

The nature of the chemical bonding between NO and open-shell Ni-II ions docked in a metal-organic framework is fully characterized by EPR spectroscopy and computational methods. High-frequency EPR experiments reveal the presence of unsaturated Ni-II ions displaying five-fold coordination. Upon NO adsorption, in conjunction with advanced EPR methodologies and DFT/CASSCF modelling, the covalency of the metal-NO and metal-framework bonds is directly quantified. This enables unravelling the complex electronic structure of Ni-II-NO species and retrieving their microscopic structure.