Ultraslow Relaxation of Toroidal State in Ferrotoroidal Dysprosium Complex

Molecular systems are emerging candidates for quantum information science (QIS) due to their unique quantum behaviors and structural tunability, opening avenues for next-generation quantum technologies. While molecular nanomagnets (MNMs) have emerged as promising spin-based qubit candidates, achieving long coherence times and feasible readouts remains challenging. Among molecular nanomagnets, single-molecule toroics (SMTs) stand out as a particularly promising class, offering magnetically silent ground states, along with the unique ability to modulate their intrinsic chirality. Realizing toroidal states in molecular systems remains a significant hurdle, with the design and stabilization of ferrotoroidal (FT) moments posing an even greater level of complexity. Moreover, the anticipated slow relaxation of toroidal states has not been explicitly demonstrated, limiting their viability in molecular quantum devices. In this work, we report a tridecanuclear [Ga₇Dy₆(N-mdea)₆(ClCH₂COO)₆(NO₃)₆(OH)₁₂(H₂O)₆]·3Cl (1) complex, which exhibits an FT ground state. Remarkably, this complex shows slow relaxation of the toroidal states, experimentally observed for the first time, with a quantum tunneling of magnetization (QTM) relaxation time of ∼3.5 × 10⁸ s (∼11 years), far surpassing the relaxation times reported for state-of-the-art Dy(III) based single-molecule magnets. The robust FT ground state in complex 1 is unequivocally established by μSQUID and corroborated by ab initio calculations, marking a major advance in the field of SMTs. This ultraslow relaxation, arising from quenched many-body tunneling processes, lays the foundation for integrating toroidal states into quantum technologies and offers a new design paradigm for molecular complexes in QIS.