Effect of Second Sphere Interactions on the Magnetic Anisotropy of Lanthanide Single-Molecule Magnets: Electrostatic Interactions and Supramolecular Contacts

To study how second-sphere interactions affect single-molecule magnet (SMM) properties of mononuclear lanthanide systems, two dysprosium(III) complexes [Dy(N-NCS)3(H2O)5]·0.45(KSCN)(18-crown-6) (1) and [Dy(NO3)2(N-NCS)3(H2O)]·(H2O)(NH4)22(18-crown-6) (2) were synthesized and characterized by single-crystal X-ray diffraction, ac, dc magnetometry, and multireference ab initio calculations. For 1, DyIII complexes are encapsulated between two crown ether molecules, while crown ether molecules and DyIII complexes crystallize in separate rows for 2. Ab initio calculations indicate that encapsulation is detrimental for magnetic anisotropy in the case of 1. This effect is related to a mismatch of the anisotropy axis of the DyIII complex and the symmetry axis of the encapsulating crown ether molecules. Ab initio calculations show that the reorientation of the electrostatic potential exerted by the crown ethers to a more symmetric position produces an enhancement of magnetic anisotropy. We tested the general charac...