A variety of metal–organic and supramolecular networks constructed from a new flexible multifunctional building block bearing picolinate and terephthalate functionalities: hydrothermal self-assembly, structural features, magnetic and luminescent properties?

RSC Advances Pub Date: 2015-10-08 DOI: 10.1039/C5RA16580F

Abstract

A novel flexible multifunctional building block (H3L) bearing picolinate and terephthalate functionalities was designed and applied for the hydrothermal self-assembly generation of a series of coordination compounds [Co(H2L)2(H2O)2] (1), [M(HL)(H2O)]n {M = Cd (2) and Mn (3)}, {[Mn1.5(L)(phen)(H2O)2]·H2O}n (4), [Zn3(L)2(H2O)6]n (5), and {[Zn3(L)2(py) (H2O)4]·4H2O}n (6) {wherein H3L = 2-(4-carboxypyridin-3-yl)-terephthalic acid, phen = 1,10-phenanthroline, py = pyridine}. All the obtained products 1–6 were fully characterized by IR spectroscopy, elemental, thermogravimetric, powder and single-crystal X-ray diffraction analyses. By adjusting the molar ratio of NaOH and H3L ligand, the latter becomes partially deprotonated to form the H2L? blocks in 1 and HL2? moieties in 2 and 3, or completely deprotonated to create the L3? units in 4–6. The structures of the obtained compounds range from a discrete 0D monomer 1 and 1D coordination polymers 4 and 5 to 2D coordination polymers 2 and 3, and an intricate 3D metal–organic framework 6; their detailed topological classification was also performed. The structures of 1–5 are further extended [0D → 3D (1), 1D → 3D (4, 5), and 2D → 3D (2, 3)] into supramolecular networks by means of multiple hydrogen bonds. The results reveal that the nature of metal(II) ion, molar ratio between NaOH and H3L ligand, and the presence (optional) of auxiliary ligand play a significant role in determining dimensionality, topology and other structural features of the obtained products. Magnetic susceptibility measurements indicate that compounds 3 and 4 have dominating antiferromagnetic couplings between metal centers. Furthermore, luminescent properties of 2, 5, and 6 were also investigated.

Graphical abstract: A variety of metal–organic and supramolecular networks constructed from a new flexible multifunctional building block bearing picolinate and terephthalate functionalities: hydrothermal self-assembly, structural features, magnetic and luminescent properties
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