A cadmium(II)- and a nickel(II)-polymer with azide and 1,3-bis(4-pyridyl)propane ligands showing neutral pentanuclear cluster-based 3D MOF and self-interpenetrated 2D undulated layer

Two coordination polymers with the same mixed ligands but different metal ion, [Cd5(bpp)6(μ1,1-N3)6(μ2-Cl)2Cl2]n (1) and {[Ni2(bpp)4(N3)4]·0.5H2O}n (2) (bpp = 1,3-bis(4-pyridyl)propane), have been hydrothermally synthesized and fully structural characterized. Complex 1 exhibits an eight-connected bcu-type 3D framework with end-on azido-aggregated neutral pentanuclear clusters periodically extended by neutral bpp linkers. Instead, 2 reveals an interpenetrated 2D (4, 4) undulated layer assembled from the octahedral Ni(II) nodes and bridging bpp connectors with monodentate azide anions terminally attached on both sides. Additionally, in contrast to non-fluorescent 2, solid complex 1 displays an intense luminescent emission resulted from the ligand-to-metal charge-transfer upon the cation binding.