Synthesis and Structural Investigation of New Triptycene-Based Ligands: En Route to Shape-Persistent Dendrimers and Macrocycles with Large Free Volume

Triptycene was used to build a series of ligands containing pyrazine groups for use in forming coordination
frameworks and as model compounds toward target shape-persistent dendrimers and macrocycles. The
phenylenediamine precursors are formed by controlled double nitration/reduction of triptycene, followed
by condensation with triptycenyl o-quinone to form the ligands. Solid-state structures show that the ligands
favor packing in layered structures with intermolecular π stacking. Increasing the length of the wings
still allows for effective packing, but increasing the number of pyrazine groups or adding more triptycenyl
moieties reduces packing efficiency. To demonstrate the potential of these molecules to function as ligands,
a coordination complex of 15 with copper(I) iodide was obtained and found to form dimers that pack
into a layered arrangement.