A series of germanotungstate-based 3d-4f heterometallic compounds with visible-light induced photocatalytic, electrochemical and magnetic properties

A series of 3d-4f heterometallic germanotungstate dimers {[Cu(dap)(H₂O)₃][LnCu₃(dap)₃(OH)₃(H₂O)₂(GeW₁₁O₃₉)]}⋅nH₂O (Ln = Sm^Ⅲ, n = 11 (1), Eu^Ⅲ, n = 12 (2), Gd^Ⅲ, n = 10 (3) and Tb^Ⅲ, n = 13 (4); dap = 1, 2-diaminopropane) have been prepared under hydrothermal conditions and structurally characterized by IR, UV–Vis, XRD, and X-ray single-crystal diffraction. Compounds 1–4 are essentially isomorphic and display organic-inorganic hybrid dimeric structures consisting of [LnCu₃(dap)₃(OH)₃(H₂O)(GeW₁₁O₃₉)]₂⁴⁻ with two supporting [Cu(dap)(H₂O)₃]²⁺ cations on both sides. The four compounds all exhibit the excellent photocatalytic activities to degradation of methylene blue (MB) and rhodamine-B (RhB) under visible light irradiation in the presence of H₂O₂. Additionally, 1–4 displays an apparent electrocatalytic activity for the reduction of hydrogen peroxide. The variable-temperature magnetic studies show that the magnetic behaviours of 1, 2 and 4 are dominated by antiferromagnetic coupling interactions, while that of 3 is ferromagnetic interactions coexist along with antiferromagnetic interactions.