Rigid Dysprosium(III) Single‐Molecule Magnets Exhibit Preserved Superparamagnetism in Solution

Comprehensive Summary Molecules with long preserved magnetic moments are perceived as the smallest units for storing bytes, which could bring a new revolution for information technology. However, the rational design of such molecules remains challenging. Here two rigid adamantanol ligand based dysprosium(III) complexes ([Dy(1‐AdO) 2 (py) 5 ]BPh 4 ‐ 1 and [Dy(2‐AdO) 2 (py) 5 ]BPh 4 ‐ 2) with pentagonal‐bipyramidal coordination geometry and local D 5h symmetry were successfully prepared, which display excellent single‐molecule magnet (SMM) behavior ( U eff ≈ 1835 K, T B ZFC ≈ 24 K, T B 100s ≈ 17 K and T B H = 23 K for 1; U eff ≈ 1756 K, T B ZFC ≈ 20 K, T B 100s ≈ 16 K and T B H = 23 K for 2) due to the much weakened vibration in low energy regimes. Remarkably, the large energy barriers and high blocking temperatures for these two complexes in solid states are well preserved in solution. This is never observed in previous studies of SMMs, indicating that the adamantanol is rigid and can be introduced to make the composed molecules stable enough to maintain the solid state magnetic property in solution.