Organic/Inorganic/Materials Chemistry Seminars
Boekelheide Lecture Series

Professor Graham Bodwell, Memorial University of Newfoundland
Hosted by Mike Haley

[n](2,11) Teropyrenophanes: Models for Probing Armchair Edge Chemistry in Nanocarbons and a Platform for the Design of Mixed Cyclophanes with Unusual Properties

Teropyrene, a C36 PAH, is the largest PAH to have been systematically bent out of planarity through its incorporation into a series of [n]cyclophanes (those that consist of a single aromatic system and a single aliphatic bridge).[1] In this series of cyclophanes (1, n = 7-10), the end-to-end bend in the teropyrene ranges from q = 145° to 178°. The teropyrene system undergoes highly regioselective electrophilic aromatic substitution (bromination) and this can be understood in terms of a combination of steric and electronic effects. Furthermore, the chemical reactivity of the teropyrene system toward bromination increases substantially as it becomes more bent.[2] The K-regions can also be oxidized to afford diones that have been π-extended to afford a series of [n]heterocyclophanes. APEX chemistry has also been achieved with high regioselectivity in the synthesis of a cyclophane with C84 aromatic system.

More recently, a large, strained (SE = 44.2 kcal/mol) and conformationally flexible mixed [3.3]cyclophane of pyridine and teropyrene (2) was synthesized using two intramolecular Wurtz coupling reactions and an unprecedented Scholl reaction between the unreactive 2 positions of the pyrene systems in a triply-bridged pyrenophane.[3] Protonation of the pyridine unit results in a greatly enhanced preference for nesting in the cavity of the highly bent teropyrene system (qcalc = 162.6°) and emergence of a charge transfer absorption band (lmax = 592 nm) due to a long range (5.0-5.5 Å), through-space intramolecular transition between the teropyrene and pyridinium units, which does not exist in the neutral cyclophane

References
1. Unikela, K. S.; Ghods Ghasemabadi, P.; Houska, V.; Dawe, L. N.; Zhao, Y.; Bodwell, G. J. “Chem. – Eur. J. 2021, 27, 390–400
2. Unikela, K. S.; Roemmele, T. L.; Houska, V.; McGrath, K. E.; Tobin, D. M.; Dawe, L. N.; Boeré, R. T.; Bodwell, G. J. Angew. Chem. Int. Ed. 2018, 57, 1707–1711.
3. Ghods Ghasemabadi, P.; Tabasi, Z. A.; Salari, P.; Zhao, Y.; Bodwell, G. J. Chem. – Eur. J. 2023, 29, e202302404