Single Crystal Electron Paramagnetic Resonance with Dielectric Resonators of Mononuclear Cu2+ Ions in a Metal–Organic Framework Containing Cu2 Paddle Wheel Units

Abstract

Dielectric resonator aided sensitivity-enhancing electron paramagnetic resonance was successfully applied to small single crystals of the previously reported metal–organic framework compound ∞3[Cu2ICu2II(H2O)2L2Cl2] in a conventional X-band EPR spectrometer at 7 K sample temperature to reveal the nature of mononuclear Cu2+ ion defect species. We found that these paramagnetic defects are not related to an impurity phase or extraframework species of the parent metal–organic framework material but are formed within the framework. Novel angular resolved single crystal continuous wave electron paramagnetic resonance supported by powder measurements and single crystal X-ray diffraction on this metal–organic framework compound identified defective copper paddle wheel units with one missing Cu2+ ion as the observed mononuclear paramagnetic species in this compound. The sensitivity enhancement by an estimated factor of 8.6 for the single crystal electron paramagnetic resonance spectroscopy is required to efficient...