Formation of Molecular Ladder Elements with Macrocyclic Platforms via Linear Bifunctional Ligands

Reaction between 4-aminopyridine and a dinuclear zinc(II) component of a Robson macrocyclic ligand has resulted
in the formation of a molecular ladder element motif. X-ray single crystal structural analysis indicates that two
pyridine rings are assembled at the same direction of the macrocycle, which are placed in a nearly parallel way
via π−π interactions, forming a concavity structure with a macrocyclic base. It is significantly noted that one hydrogen-bond cycle generated from hydrogen atoms of two amino groups with two perchlorate anions has sustained such
an assembly of two 4-aminopyridine species to stand in a face to face pattern through a weak molecular interaction
on the macrocyclic platform by one-end coordination bonding. The self-assembly of 4-carboxylic pyridine acid and
the same macrocyclic component in the presence of sodium hydroxide has yielded an interesting wheellike complex.
Two macrocyclic dinuclear zinc(II) components have been linked through coordination bonding with two pyridine
derivatives situated on the same direction of a macrocycle. X-ray structural results suggest that the compound has
a unique sandwichlike structure consisting of two macrocyclic covers with two inversely positioned bridging pyridine
carboxylic groups in the middle.