On the Supra-LUMO Interaction: Case Study of a Sudden Change of Electronic Structure as a Functional Emergence |
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Authors: | Alexis Gosset Dr. Štěpánka Nováková Lachmanová Dr. Sawsen Cherraben Dr. Gildas Bertho Jérémy Forté Dr. Christian Perruchot Dr. Henri-Pierre Jacquot de Rouville Dr. Lubomír Pospíšil Dr. Magdaléna Hromadová Dr. Éric Brémond Dr. Philippe P. Lainé |
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Affiliation: | 1. Université de Paris, CNRS, ITODYS, 75006 Paris, France;2. J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 3, 182 23 Prague, Czech Republic;3. Université de Paris, Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques CNRS UMR 8601, 45 rue des Saints-Pères, 75270 Paris Cedex 06, France;4. Sorbonne Université, UMR CNRS 8232, Institut Parisien de Chimie Moléculaire, 4 place Jussieu, 75005 Paris, France |
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Abstract: | The synergistic functioning of redox-active components that emerges from prototypical 2,2′-di(N-methylpyrid-4-ylium)-1,1′-biphenyl is described. Interestingly, even if a trans conformation of the native assembly is expected, due to electrostatic repulsion between cationic pyridinium units, we demonstrate that cis conformation is equally energy-stabilized on account of a peculiar LUMO (SupLUMO) that develops through space, encompassing the two pyridiniums in a single, made-in-one-piece, electronic entity (superelectrophoric behavior). This SupLUMO emergence, with the cis species as superelectrophore embodiment, originates in a sudden change of electronic structure. This finding is substantiated by insights from solid state (single-crystal X-ray diffraction) and solution (NOE NMR and UV-vis-NIR spectroelectrochemistry) studies, combined with electronic structure computations. Electrochemistry shows that electron transfers are so strongly correlated that two-electron reduction manifests itself as a single-step process with a large potential inversion consistent with inner creation of a carbon-carbon bond (digital simulation). Besides, absence of reductive formation of dimers is a further indication of a preferential intramolecular reactivity determined by the SupLUMO interaction (cis isomer pre-organization). The redox-gated covalent bond, serving as electron reservoir, was studied via atropisomerism of the reduction product (VT NMR study). The overall picture derived from this in-depth study of 2,2′-di(N-methylpyrid-4-ylium)-1,1′-biphenyl proves that trans and cis species are worth considered as intrinsically sharply different, that is, as doubly-electrophoric and singly-superelectrophoric switchable assemblies, beyond conformational isomerism. Most importantly, the through-space-mediated SupLUMO may come in complement of other weak interactions encountered in Supramolecular Chemistry as a tool for the design of electroactive architectures. |
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Keywords: | electronic structure electrostatic interactions pyridinium structure-activity relationships supramolecular electrochemistry |
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