Synthesis, luminescent and magnetic properties of new tetranuclear lanthanide complexes with 4-hydroxy-2,1,3-benzothiadiazolate and dibenzoylmethanide ligands

Four new tetranuclear complexes, [Ln4(dbm)4(O-btd)6(OH)2] 1a (Ln = Yb), 1b (Ln = Dy) and [Ln4(dbm)6(O-btd)4(OH)2] 2a (Ln = Yb), 2b (Ln = Dy) (O-btd = 4-hydroxo-2,1,3-benzothiadiazolate and dbm = dibenzoylmethanide), and their solvates with toluene and tetrahydrofuran were synthesized. The magnetic properties of the complexes 1a, 1b, 2a and 2b have been studied, revealing different magnetic susceptibility patterns for the Yb(III) and Dy(III) complexes in the temperature range 80–300 K. Upon lowering the temperature, a weak antiferromagnetic ordering is observed for both Yb compounds, while the Dy derivatives are assumed to show weak ferromagnetic interactions. The Yb complexes 1a and 2a demonstrate strong NIR luminescence at ∼1000 nm in CH2Cl2 solution upon excitation of the (O-btd)− ligand. This observation suggests the (O-btd)− ligand to be an efficient antenna ligand for lanthanide-based NIR luminescence.