Measurement of the Quantum Tunneling Gap in a Dysprosocenium Single-Molecule Magnet

We perform magnetization sweeps on the high-performing single-molecule magnet [Dy(Cp^ttt)₂][B(C₆F₅)₄] (Cp^ttt = C₅H₂Bu₃-1,2,4; Bu = C(CH₃)₃) to determine the quantum tunneling gap of the ground-state avoided crossing at zero-field, finding a value on the order of 10^-7 cm^-1. In addition to the pure crystalline material, we also measure the tunnel splitting of [Dy(Cp^ttt)₂][B(C₆F₅)₄] dissolved in dichloromethane (DCM) and 1,2-difluorobenzene (DFB). We find that concentrations of 200 or 100 mM [Dy(Cp^ttt)₂][B(C₆F₅)₄] in these solvents increases the size of the tunneling gap compared to the pure sample, despite a similarity in the strength of the dipolar fields, indicating that either a structural or vibrational change due to the environment increases quantum tunneling rates.