Metal(II) Complexes Based on Benzene-1,2,3-triyldioxy-triacetate: Structures and Photoluminescence Properties

Using a novel hemirigid multitopic ligand, benzene-1,2,3-triyldioxy-triacetic acid (H₃L), five metal­(II) complexes formulated as Cd₃L₂(H₂O)₃·H₂O (1), Zn­(L)­(BPPA)_¹/2·(HBPPA) (BPPA = N,N′-bis-(4-pyridyl)­phthalamide) (2), M­(HL)­(phen)­(H₂O)₂·H₂O (phen = phenanthroline) (M = Zn (3) and Co (4)) and Cd­(HL)­(2,2′-bpy)­(H₂O)·5H₂O (2,2′-bpy = 2,2′-bipyridine) (5) have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complex 1 features a 2-nodal (4, 5)-connected three-dimensional (3D) LIBNIU net with a (3.4².5.6.7)­(3².4³.5.6².7.8) topology. Complex 2 exhibits a 2-nodal (3, 4)-connected two-dimensional (2D) framework with a novel (4.7.8)­(4.7⁴.8) topology, in which the μ₂-BPPA is self-penetrated into a cage of the 2D layer constructed by neighboring six Zn­(II) ions and six L^3–. Complexes 3 and 4 are isostructural, and they are mononuclear Zn­(II) and Co­(II) complexes, respectively, in which strong intramolecular π–π stacking interactions are observed between phen and the phenyl ring of HL^2–. Complex 5 is a mononuclear Cd­(II) complex, which is assembled into 3D supramolecular architecture via strong intermolecular π–π stacking interactions and H bonds. L^3– or HL^2– displays different coordination modes in the five complexes. Complexes 1–3 and 5 show different UV absorptions, emission spectra, and photoluminescence lifetimes.