Synthesis and Crystallographic Characterization of Low-Dimensional and Porous Coordination Compounds Capable of Supramolecular Aromatic Interaction Using the 4,4‘-Azobis(pyridine) Ligand

Coordination compounds with a 4,4‘-azobis(pyridine) (azpy) ligand, {[M2(azpy)6(H2O)5]·4PF6·azpy·H2O}n (M = NiII
(1) or CoII (2)) (0-dimensional (0-D) dimer), {[Zn(azpy)3(H2O)2]·2PF6·2azpy·4H2O}n (3) (1-dimensional (1-D) fishbone-type chain), {[Ag(azpy)]·PF6}n (4) (1-D linear chain), {[Mn(NCS)2(azpy)2]·azpy}n (5) (2-dimensional (2-D) grid sheet),
and {[Ni(NCS)2(azpy)2]·3toluene}n (6) (2-D grid sheet), were synthesized and structurally characterized. Compounds
1 and 2 have a 0-D dimer motif, in which one MII (MII = NiII or CoII) coordination site is shared by unidentate azpy
and H2O ligands, each with half-occupancy, i.e., exhibiting static disorder. Compounds 3 and 4 afford 1-D fishbone-type and 1-D linear chain motifs, respectively. Azpy mediates π−π and π−p interactions between these low-dimensional structures. Compounds 5 and 6 possess a 2-D grid sheet motif. These sheets assemble to form
microporous frameworks that incorporate aromatic guests, such as coordination-free azpy (5) and toluene (6).
There exist not only π−π and π−p interactions but also CH−π interactions between the framework azpy ligands
and guests. It should be noted that the azpy ligand is a good candidate for the construction of new assembling
systems of coordination compounds through its aromatic interactions.