Organic–Inorganic Hybrid Coordination Polymers Based on 6-Methylpyridine-2,4-dicarboxylic Acid N-Oxide (MPDCO) Ligand: Preparations, Interpenetrating Structures, and Magnetic and Luminescent Properties

Eight novel coordination polymers based on the 6-methylpyridine-2,4-dicarboxylic acid N-oxide (MPDCO) ligand, [M(MPDCO)(H 2 O) x ] n (M = Mn 2+, x = 1 ( 1 ); M = Cu 2+, x = 2 ( 2 )), [M(MPDCO)(bpy)(H 2 O)·(H 2 O)] n (M = Co 2+ ( 3 ), Ni 2+ ( 4 )), [M(MPDCO)(TPB) 0.5 (H 2 O) · (H 2 O) x ] n (M = Co 2+ ( 5 ), Ni 2+ ( 6 ), Zn 2+ ( 7 ), Cd 2+ ( 8 )) (bpy = 4,4′-bipyridine, TPB = 1,2,3,4-tetra-(4-pyridyl)-butane) have been prepared and structurally characterized. Compounds 1 and 2 are both two-dimensional (2-D) layers, which are further stacked via strong interlayer hydrogen-bond interactions to form three-dimensional (3-D) supramolecular structures. Compounds 3 and 4, which contain 3-fold interpenetrating nets, are isostructural and feature 3-D (10,3)-d open frameworks. In isomorphous compounds 5 – 8, 2-D sheets with nonequivalent nodes of (4 2 ·6 2 ·8 2 )(4·6 2 ) 2 topology were constructed from metal cations, MPDCO, and the four-connecting ligand 1,2,3,4-tetra-(4-pyridyl)-butane (TPB). Then the inclined interpenetration of these 2-D sheets leads to 3-D porous architectures with rhombic channels that embody some disordered water molecules. Dominant antiferromagnetic coupling was observed in compounds 1, 3, and 4 . The compounds 7 and 8 both exhibit strong fluorescent emissions in the solid state and may be suitable as candidates of blue-fluorescent materials.