Unveiling the atomistic and electronic structure of NiII–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 NiII 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 NiII 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 NiII–NO species and retrieving their microscopic structure.