Crystal Engineering Gone Awry. What a Difference a Few Methyl Groups Make in Fullerene/Porphyrin Cocrystallization

Abstract

Two related nickel(II) porphyrins, etioporphyrin-I (Etio-I) and octaethylporphyrin (OEP), were cocrystallized with C70 to produce the new cocrystal structures C70·Ni(Etio-I)·2C6H6 and C70·Ni(OEP)·2C6H6. Etio-I is a variant of OEP, where four alternating ethyl groups from OEP are replaced with methyl substituents. This isomer of etioporphyrin has the potential to act as an agent in chiral sorting of asymmetric fullerenes. However, the replacement of four ethyl groups has nontrivial structural consequences. Further host–guest investigation of M(Etio-I) (M = Co, Ni, Cu, Zn) with C60 or C70 was conducted, producing new X-ray structures of Co(Etio-I) and Zn(Etio-I), and a redetermination of Ni(Etio-I). Despite numerous and varied attempts, C60 cocrystallized with M(Etio-I) could not be obtained.