A porous coordination polymer with a fourfold interpenetrating β-hydroquinone framework constructed from bis(dibenzoylmethanato) cobalt(II) and tridentate quaterpyridine ligand

Abstract

Bis(β-diketonato) Co(II) complex, [Co(dbm)2] (dbm = dibenzoylmethanato or 1,3-diphenyl-propane-1,3-dionato), was examined as a linear building block for the construction of coordination polymers in the combination with a potentially tridentate ligand, 2,6-bis(4′-pyridyl)-4-(3′-pyridyl)pyridine (L1). L1 was expected to work as a conformationally flexible ligand because of the rotation of the terminal 3-pyiridyl moiety. A porous coordination polymer, [Co(dbm)2]3/2(L1)·(G) (Co-1, G = guest molecules) with a fourfold interpenetrating β-hydroquinone framework was obtained from a methanol–nitrobenzene–benzonitrile mixed solution containing [Co(dbm)2(H2O)2] and L1. Single crystal X-ray diffraction analysis reveals that Co-1 crystallizes in a trigonal space group R-3 with unit-cell parameters, a = b = 53.8629(12), c = 14.0649(7) Å, and V = 35338(3) Å3. Solvent molecules were indicated to be included in the large hexagonal channel from thermogravimetry and elemental analyses, while they could not be determined from X-ray analysis because of the severe disorder. Meanwhile, a 2-D (6. 3) coordination polymer (Co-2) was obtained from the nitrobenzene-methanol mixed solution. In Co-2, [Co(dbm)2] and L1 also work as a linear building block and a tridentate ligand, respectively. Moreover, a coordination polymer with a 1-D chain structure (Co-3) was obtained from a hydrothermal synthetic condition. In Co-3 with no guest molecules, [Co(dbm)2] works as a linear building block, while L1 behaves as a bidentate ligand. Comparison of the three structures indicates the templating role of solvent molecules in forming the β-hydroquinone framework of Co-1.