Single crystal structures have been determined for the three cofacial, oxygen-bridged, silicon phthalocyanine oligomers, [((CH3)(3)SiO)(2)(CH3)SiO](SiPcO)(2-4)[Si(CH3)(OSi(CH3)(3))(2)], and for the corresponding monomer. The data for the oligomers give structural parameters for a matching set of three cofacial, oxygen-bridged silicon phthalocyanine oligomers for the first time. The staggering angles between the six adjacent cofacial ring pairs in the three oligomers are not in a random distribution nor in a cluster at the intuitively expected angle of 45 degrees but rather are in two clusters, one at an angle of 15 degrees and the other at an angle of 41 degrees. These two clusters lead to the conclusion that long, directional interactions (LDI) exist between the adjacent ring pairs. An understanding of these interactions is provided by atoms-in-molecules (AIM) and reduced-density-gradient (RDG) studies. A survey of the staggering angles in other single-atom-bridged, cofacial phthalocyanine oligomers provides further evidence for the existence of LDI between cofacial phthalocyanine ring pairs in single-atom-bridged phthalocyanine oligomers.