Steric Repulsion Induced Conformational Switch in Supramolecular Structures.
Inspired by the rigidified architecture of 'picket-fence' systems, we propose a strategy utilizing strain to impose intramolecular tension in already peripherally overcrowded structures leading to selective atropisomeric conversion. Employing this approach, tuneable shape-persistent porphyrin conformations were acquired exhibiting distinctive supramolecular nanostructures based on the orientation of the peripheral groups. The intrinsic assemblies driven by non-covalent bonding interactions form supramolecular polymers while encapsulating small molecules in parallel channels or solvent-accessible voids. The developed molecular strain engineering methodologies combined with synthetic approaches have allowed the introduction of the pivalate units creating a highly strained molecular skeleton. Changes in the absorption spectrum indicated the presence of severe steric repulsions between the peripheral groups which were confirmed by single crystal X-ray analysis. To release the steric strain introduced by the peripheral units, thermal equilibration strategies were used to selectively convert the most abundant atropisomer to the desirable minor one.
['Norvaiša|Karolis|K|http://orcid.org/0000-0003-3219-8739', 'Maguire|Sophie|S|http://orcid.org/0000-0003-1110-8730', 'Donohoe|Claire|C|http://orcid.org/0000-0003-2468-9431', "O'Brien|John E|JE|", 'Twamley|Brendan|B|', 'Gomes-da-Silva|Ligia C|LC|http://orcid.org/0000-0003-0624-8819', 'Senge|Mathias O|MO|http://orcid.org/0000-0002-7467-1654']
Atropisomers Crystallography NMR Porphyrinoids Supramolecular Chemistry