A Mononuclear Transition Metal Single-Molecule Magnet in a Nuclear Spin-Free Ligand Environment

The high-spin pseudotetrahedral complex
[Co­(C3S5)2]2– exhibits
slow magnetic relaxation in the absence of an applied dc magnetic
field, one of a small number of mononuclear complexes to display this
property. Fits to low-temperature magnetization data indicate that
this single-molecule magnet possesses a very large and negative axial
zero-field splitting and small rhombicity. The presence of single-molecule
magnet behavior in a zero-nuclear spin ligand field offers the opportunity
to investigate the potential for this molecule to be a qubit, the
smallest unit of a quantum information processing (QIP) system. However,
simulations of electron paramagnetic resonance (EPR) spectra and the
absence of EPR spectra demonstrate that this molecule is unsuitable
as a qubit due to the same factors that promote single molecule magnet
behavior. We discuss the influence of rhombic and axial zero-field
splitting on QIP applications and the implications for future molecular
qubit syntheses.