Switching the coordination geometry to enhance erbium(Ⅲ)single-molecule magnets

Two erbium(Ⅲ)complexes[ErCl(OArAd)3][Na(THF)6](1)and Er(OArAd)3(2)are successfully prepared by using one variety of"hard"base ligand with large steric hindrance.The coordination geometry around the Er(Ⅲ)site changes from distorted tetrahedral to flat trigonal pyramid geometry in different solvent environment due to the removal of the coordinated chloride.Such an alternation significantly enhances the single-molecule magnet(SMM)behavior and makes the field-induced effective energy barrier(Ueff)arrive at 43(1)cm-1 for the latter.Together with theoretical calculations,this study shows that strong equatorial ligand field and high local symmetry are critical to suppress the quantum tunneling of the magnetization(QTM)and achieve high-performance erbium(Ⅲ)based SMMs.