Opening magnetic hysteresis via improving the planarity of equatorial coordination by hydrogen bonding.

Through a mixed-ligand strategy, the structural change from a discrete dinuclear Dy III cluster to a one-dimensional polymeric chain was achieved, maintaining the two magnetic entities with the same {Dy(dppbO 2 ) 2 (H 2 O) 5 } (dppbO 2 = 1,4-butylenebis(diphenylphosphine oxide)) core structure. Since the hydrogen bonding between the equatorial coordinated water molecules and the guests/solvents/anions is distinct, the local geometry and the equatorial planarity of the first coordination sphere of the central Dy III ion become slightly different caused by the second coordination sphere. As a result, the dinuclear compound shows typical butterfly-shaped hysteresis loops, while it significantly opens at zero magnetic field up to 11 K for the 1D polymer, which is unprecedented in coordination polymers. Our experimental observations and theoretical analysis indicate that the hydrogen bonding leads to the fine-tuning of certain bond lengths and angles of the coordination environment, as well as the crystal field to a certain extent, revealing that the second coordination sphere affects the first coordination sphere by hydrogen bonding.