Low-Coordinate Single-Ion Magnets by Intercalation of Lanthanides into a Phenol Matrix

It is very challenging to synthesize stable trivalent rare-earth complexes in which the coordination number is lower than 3 for the high oxidation state, there is a large ion radius and nearly non-bonding character of trivalent lanthanide ions. The bulky phenol ligand ArOH (Ar = 2,6-Dipp(2)C(6)H(3), Dipp = 2,6-diisopropylphenyl) was utilized to construct low-coordinate lanthanide compound [(ArO)Ln-(OAr')] (Ar' = 6-Dipp-2-(2'-Pr-i-6-CHMe(CH2-)C6H3)-C6H3O-; Ln = Tb, Dy, Ho, Er, Tm). These complexes and the free ligand ArOH were isostructural. Magnetic measurements and theoretical studies demonstrated that both the oblate-type dysprosium and prolate-type erbium analogues exhibited single-ion magnet (SIM) behavior. The bulky phenol ligands provided strong uniaxial ligand field, making the dysprosium SIM possessing blocking barrier up to 961 K.