Relieving frustration: The case of antiferromagnetic Mn3 molecular triangles

Recently, various triangular [Mn-III](3) molecules have been extensively studied due to the fact that one can modulate the magnitude and the sign of the inter-ion exchange, thereby giving rise to very simple clusters that constitute some of the cleanest and best examples of so-called single-molecule magnets. However, magnetic and electron paramagnetic resonance (EPR) characterizations of low-spin antiferromagnetic [Mn-III](3) complexes have been problematic due to the significant spin frustration that exists for this topology. We show that this frustration is relieved in the highly distorted [NEt4](3)Mn3Zn2(salox)(3)O(N-3)(8)]center dot MeOH molecule: Susceptibility data suggest a well isolated S = 2 ground state; EPR spectroscopy and high-field torquemetry support this conclusion and further indicate the presence of a very significant zero-field-splitting (zfs) separating the lowest-lying m(S) = +/- 2 states from the excited levels within the same S = 2 multiplet. Remarkably, this zfs is sufficient to give rise to magnetic bistability, as evidenced through the observation of low-temperature magnetization hysteresis.