Phthalocyanines, macrocyclic compounds composed of an aromatic carbon ring system interlaced with nitrogen, 1 can be chelated by a metal or metalloid and are utilized as an industrial dye, in solar energy applications, and cancer treatments. Silicon-substituted phthalocyanines can form dimeric compounds through siloxane chains (Figure ). When examined through X-ray crystallography, observed torsional ring-to-ring rotation angles of approximately 15 and 40 degrees run counter to expected confirmations, potentially implying the presence of an unknown intramolecular force, these forces have been dubbed long, directional interactions (LDIs). To date, structural data has been gathered on twenty such uniquely functionalized dimers, with further investigations into this phenomenon requiring new functional groups to be selected and utilized in the generation of dimeric phthalocyanines.