Structural and fluorescent diversities of Cd(II)/Zn(II) phosphonates with varying auxiliary ligands

Abstract

Six new transition metal phosphonates, [Cd(H2L)(H2O)]n (1), [Cd2(H2L)2(H2O)]n (2), [Cd4(H2bmt)2(H2O)]n (3), {[Cd2(H4bmt)2(2, 2′-bipy)2]·4H2O} (4), [Zn(H4bmt)(2, 2′-bipy)]n (5) and [Zn3(bmt)(4, 4′-bipy)2]n (6), H4L = (benzylazanediyl)bis(methylene)-diphosphonicacid,H6bmt = (benzene-1,3,5-triyltris(methylene))triphosphonic acid, have been synthesized by H4L or H6bmt as well as auxiliary ligands under hydrothermal conditions and characterized by elemental analysis, IR, XRD and single-crystal X-ray diffraction. Structural analysis indicates that complexes 1–6 feature 0D-3D structures. The introduction of auxiliary ligands including 4, 4′-Vinylenedipyridine, 4-Cyanopyridine, 4, 4′-bipy, 2, 2′-bipy and H6TTHA (1,3,5-triazine-2,4,6-triamine hexaacetic acid) increases the crystallinity and controls the dimensionality of the final complexes. The fluorescence emission properties of 1–6 and the free ligands were investigated in the solid state at room temperature. Moreover, the fluorescence lifetime (τ) and quantum yield (Φf) were measured to further characterize the fluorescence properties. The results are compared to illustrate the influence of the auxiliary ligands and structure difference on the fluorescence properties.