Novel mononuclear Ln complexes with pyrazine-2-carboxylate and acetylacetonate co-ligands: remarkable single molecule magnet behavior of a Yb derivative
A series of novel isomorphic mononuclear complexes [Ln(PyrCOO)(acac)2(H2O)2] (Ln = Eu (1), Gd (2), Tb (3), Dy (4), Ho (5), Er (6), Tm (7), Yb (8), Y(9); acac− – acetylacetonate (pentane-2,4-dionate) anion, PyrCOOH is pyrazine-2-carboxylic acid) were prepared. Slow magnetic relaxation indicating SMM behavior was found in complexes 3, 4, 6 and 8. For 4 (Dy), the anisotropy barrier is Δeff/kB = 77 K under a dc field of 1500 Oe. For 8 (Yb), the anisotropy barrier is Δeff/kB = 54 K under a dc field of 2000 Oe which is the highest presently known value for molecular Yb carboxylate complexes and for Yb molecular complexes in general.