Steric Repulsion Induced Conformational Switch in Supramolecular Structures |
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Authors: | Karolis Norvai?a Sophie Maguire Claire Donohoe Dr John E O'Brien Dr Brendan Twamley Dr Ligia C Gomes-da-Silva Prof?Dr Mathias O Senge |
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Institution: | 1. School of Chemistry, Chair of Organic Chemistry Trinity Biomedical Sciences Institute Trinity College Dublin, The University of Dublin, 152–160 Pearse Street, D02 R590 Dublin 2, Ireland;2. School of Chemistry Trinity College Dublin, The University of Dublin, D02 PN40 Dublin 2, Ireland;3. CQC, Coimbra Chemistry Center Department of Chemistry, University of Coimbra, 3000-435 Coimbra, Portugal |
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Abstract: | 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. |
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Keywords: | Atropisomers Crystallography NMR Porphyrinoids Supramolecular Chemistry |
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