Halogen bonding directed supramolecular assembly in bromo-substituted trezimides and tennimides

Abstract

Reaction of isophthaloyl dichloride (I) with 2-amino-5-bromopyridine (BrO) and 2-amino-5-bromopyrimidine (26BrO) produces the trimeric (trezimide) and tetrameric (tennimide) imide-based macrocycles (BrIO)₃ and (BrIO)₄, and (26BrIO)₃ and (26BrIO)₄, respectively, in one-step and in modest yields. Macrocyclisation (forming 18-/24-membered rings) is facilitated by the imide hinge [OC–N(R)–CO] (R = ortho-N-substituted-pyridine/pyrimidine), though competing reactions also lead to considerable oligomer/polymer formation. The macrocycles (having 3 or 4 Br atoms) lack classical strong hydrogen bonding donors (i.e. N–H, O–H), but contain numerous acceptors (i.e. N_aromatic, CO, arene) participating in halogen and weaker hydrogen bonding. Five crystal structures are analysed with the macrocycles typically aggregating through short C–Br⋯OC_carbonyl and/or C–Br⋯N_aromatic halogen bonds (N_c ≤ 0.90) and often associated with longer C–Br⋯H/π(arene) contacts. Of note, (BrIO)₃ exhibits three types of Br⋯OC/π(arene) halogen bonds with Br⋯H and C–H⋯O contacts. The C–Br⋯N/O halogen bonds, in promoting overall aggregation, typically link macrocycles into 1-D halogen bonded chains.