Hydrothermal synthesis, crystal structure and fluorescence quenching of hexanuclear Ni5IILnIII complexes (Ln = La, Nd) containing macrocyclic oxamide ligands

Two novel macrocyclic oxamidato-bridged complex [La(NiL)5] (ClO4)3·DMF·1·5H2O (1) and [Nd(NiL)5](ClO4)3·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. Compound 1 crystallizes in the triclinic space group P−1 with a = 17.534(6) Å, b =  18.626(6) Å, c = 18.726(6) Å, α = 97.115(6)°, β = 114.253(5)°, γ = 108.449(5)° and Z = 2; whereas 2 crystallizes in the monoclinic system, P2(1)/n group, a = 17.805(5) Å, b = 24.073(7) Å, c = 23.570(6) Å, α = γ =  90°, β = 102.950(6)° and Z = 4. The fluorescences of NdIII are almost completely quenched in 2.