Substituent effects of auxiliary ligand in mononuclear dibenzoylmethane DyIII/ErIII complexes: Single-molecule magnetic behavior and luminescence properties
Four mononuclear rare earth complexes [(dbm)3Ln(dmbipy)] (1-Ln, Ln= Dy, Er) and [(dbm)2Ln(dmobipy)(NO3)] (2-Ln, Ln= Dy, Er) (Hdbm = dibenzoylmethane, dmbipy = 4,4'-dimethyl-2,2'-bipyridine, dmobipy = 4,4'-dimethoxy-2,2'-bipyridine) have been synthesized by tuning the substituents at 4,4'-positions of 2,2'-bipyridine. It is interesting to note that replacing the substituents of auxiliary ligands from –CH3 to –OCH3 results in major difference in molecular formula and geometries. Magnetic measurements show that slow relaxation of the magnetization appears clearly in the absence of dc field for 1-Dy, while under an applied dc field for others. Ab initio calculations reveal that the calculated effective gz value for 1-Dy is larger than 2-Dy, consistent with the experimental results. In addition, the luminescence properties of the four complexes have been studied, and 2-Dy, 1-Er and 2-Er can exhibit characteristic emissions of DyIII/ ErIII ion.