Homometallic Dy III Complexes of Varying Nuclearity from 2 to 21: Synthesis, Structure, and Magnetism

The synthesis, structure, and magnetic properties of four Dy III coordination compounds isolated as [Dy 2 (LH 2 ) 2 (μ 2 ‐η 1 :η 1 ‐Piv)]Cl ⋅ 2 MeOH ⋅ H 2 O ( 1 ), [Dy 4 (LH) 2 (μ 3 ‐OH) 2 (Piv) 4 (MeOH) 2 ] ⋅ 4 MeOH ⋅ 2 H 2 O ( 2 ), [Dy 6 (LH 2 ) 3 (tfa) 3 (O 3 P t Bu)(Cl) 3 ]Cl 4 ⋅ 15.5 H 2 O ⋅ 4 MeOH ⋅ 5 CHCl 3 ( 3 ) and [Dy 21 (L) 7 (LH) 7 (tfa) 7 ]Cl 7 ⋅ 15 H 2 O ⋅ 7 MeOH ⋅ 12 CHCl 3 ( 4 ) are reported (Piv=pivalate, tfa=1,1,1‐trifluoroacetylacetone, O 3 P t Bu= tert ‐butylphosphonate). Among these, 3 displays an equilateral triangle topology with a side length of 9.541 Å and a rare pentagonal‐bipyramidal Dy 3+ environment, whereas complex 4 exhibits a single‐stranded nanowheel structure with the highest nuclearity known for a homometallic lanthanide cluster structure. A tentative model of the dc magnetic susceptibility and the low‐temperature magnetization of compounds 1 and 2 indicates that the former exhibits weak ferromagnetic intramolecular exchange interaction between the Dy 3+ ions, whereas in the latter both intramolecular ferromagnetic and antiferromagnetic magnetic exchange interactions are present. Compounds 1 , 3 , and 4 exhibit frequency‐dependent ac signals below 15 K at zero bias field, but without exhibiting any maximum above 2 K at frequencies up to 1400 Hz. The observed slow relaxation of the magnetization suggests that these compounds could exhibit single molecule magnet (SMM) behavior with either a thermal energy barrier for the reversal of the magnetization that is not high enough to block the magnetization above 2 K, or there exists quantum tunneling of the magnetization (QTM).