Long Directional Interactions (LDIs) in Oligomeric Cofacial Silicon Phthalocyanines and Other Oligomeric and Polymeric Cofacial Phthalocyanines

Crystal structures have been determined for the three-member
set of cofacial silicon phthalocyanines, ((n-C6H13)3SiO)­[SiPcO]1–3(Si­(n-C6H13)3).
The staggering angles between adjacent rings in the dimer and trimer
of this set are ∼16°. The interactions leading to these
angles have been investigated by the atoms-in-molecules (AIM) and
reduced-density-gradient (RDG) methods. The results show that long
directional interactions (LDIs) are responsible for these angles.
A survey of the staggering angles in various cofacial phthalocyanines
described in the literature has revealed the existence of significant
LDIs in a number of them. It is apparent that in many cases the ability
of LDIs to dominate the forces giving rise to the staggering angles
observed in cofacial phthalocyanines depends on their inter-ring separations.