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

We perform magnetization sweeps on the high-performing single-molecule magnet [Dy­(Cpttt)2]­[B­(C6F5)4] (Cpttt = C5H2 t Bu3-1,2,4; t 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(Cpttt)2]­[B­(C6F5)4] dissolved in dichloromethane (DCM) and 1,2-difluorobenzene (DFB). We find that concentrations of 200 or 100 mM [Dy­(Cpttt)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.