Hydrothermal synthesis, crystal structure and fluorescence quenching in oxamidato-bridged tetranuclear Ni3IILnIII complexes containing macrocyclic ligands (Ln=Tb, Dy)

Two novel oxamidato-bridged complexes incorporating macrocyclic oxamide of formula [(NiL)3Tb(DMF)2(H2O)](ClO4)32DMF 1, [(NiL)3Dy(DMF)2](ClO4)3DMF CH3OH·H2O 2 (NiL, H2L=2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien), have been hydrothermally synthesized and structurally determined. Both crystals crystallize in the triclinic system, space group P−1, for 1a=13.959(4) Å, b=15.038(5) Å, c=19.488(6) Å, α=104.653(5)°, β=92.431(5)°, γ=97.328(5)°; for 2a=13.949(4) Å, b=15.031(4) Å, c=19.487(6) Å, α=104.633(5)°, β=92.439(5)°, γ=97.351(6)°. In both complexes, the central LnIII and external nickel ions are bridged by macrocyclic oxamide groups. Fluorescences of TbIII and DyIII are almost completely quenched in 1 and 2.