Double-walled pyr topology networks from a novel fluoride-bridged heptanuclear metal cluster

Abstract

Two isostructural metal-organic materials, Tripp-1-M (Tripp = 2,4,6-tris(4-pyridyl)pyridine; M = Co, Ni), that exhibit binodal 3,6-connected pyr network topology have been prepared and characterized. Tripp-1-M are based upon a novel M₇F₁₂²⁺ cluster that possesses 12 connection points but, because of double cross-linking by 3-connected Tripp ligands, it functions as a 6-connected supermolecular building block (SBB).

Fig. 1. (Left) Perspective and above views of the novel M₇F₁₂ ²⁺ cluster that sustains Tripp-1-M. (right) Illustration of the 12 connection points of the Co₇F₁₂ SBB in Tripp-1-Co (Co, F, N and C atoms in purple, green, blue and grey). Solvent molecules, hydrogen atoms and counter-ions are omitted for the sake of clarity.

Scheme 1. Synthesis of 2,4,6-tris(4-pyridyl)pyridine (Tripp).

Fig. 2. Illustration of the topology of Tripp-1-M. The Tripp ligand is represented by a 3-c triangle (blue) whereas the M₇F₁₂ ²⁺ SBB is reduced to a 6-c octahedron (red).

Fig. 3. The two types of double-walled cages (OC, left above; TC left, below) found in Tripp-1-M (right).

Fig. 4. Energy-dispersive X-ray spectroscopy (top) and X-ray photoelectron spectroscopy (bottom) of Tripp-1-Co.

Fig. 5. CO₂ adsorption isotherms (filled symbols) and desorption (empty symbols) for Tripp-1-Co (black) and Tripp-1-Ni (red) conducted at 195 K.

Fig. 6. CO₂ and N₂ adsorption (filled symbols) and desorption (empty symbols) isotherms for Tripp-1-Co (top) and Tripp-1-Ni (bottom) at three temperatures, 273 K, 283 K and 293 K.