Homochiral [2.2]Paracyclophane Self-Assembly Promoted by Transannular Hydrogen Bonding

• Published in: Angewandte Chemie International Edition 2016-08, Vol.55 (36), p.10726-10731
• Main Authors: Fagnani, Danielle E., Meese Jr, Michael J., Abboud, Khalil A., Castellano, Ronald K.
• Format: Article
• Language: English
• Subjects: Amides; Chemical bonds; Chirality; Construction; Crystallography; cyclophanes; Derivatives; Design; Hydrogen; Hydrogen bonding; Hydrogen bonds; Monomers; NMR; Nuclear magnetic resonance; Polymers; Self-assembly; Solid state; Stacks; Strands; supramolecular chemistry; X-ray crystallography
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201605286

[2.2]paracyclophane (pCp), unlike many π‐building blocks, has been virtually unexplored in supramolecular constructs. Reported here is the synthesis and characterization of the first pCp derivatives capable of programmed self‐assembly into extended cofacial π‐stacks in solution and the solid state. The design employs transannular (intramolecular) hydrogen bonds (H‐bonds), hitherto unstudied in pCps, between pseudo‐ortho‐positioned amides of a pCp‐4,7,12,15‐tetracarboxamide (pCpTA) to preorganize the molecules for intermolecular H‐bonding with π‐stacked neighbors. X‐ray crystallography confirms the formation of homochiral, one‐dimensional pCpTA stacks helically laced with two H‐bond strands. The chiral sense is dictated by the planar chirality (Rp or Sp) of the pCpTA monomers. A combination of NMR, IR, and UV/Vis studies confirms the formation of the first supramolecular pCp polymers in solution. Laced up: [2.2]Paracyclophane (pCp) derivatives are capable of programmed self‐assembly into extended cofacial π‐stacks in solution and in the solid state. The one‐dimensional arrangements are homochiral and helically laced‐up by a combination of transannular (intramolecular) and intermolecular hydrogen bonds. pCpTA=pCp‐4,7,12,15‐tetracarboxamide.