Shortcuts for Electron‐Transfer through the Secondary Structure of Helical Oligo‐1,2‐Naphthylenes

Abstract

Atropisomeric1 ,2-naphthylene scaffolds provide access to donor-acceptor compounds with helical oligomerbased bridges,a nd transient absorption studies revealed a highly unusuald ependenceo ft he electron-transfer rate on oligomer length, whichi sd ue to their well-defined secondary structure. Close noncovalent intramolecular contacts enable shortcuts for electron transfer that would otherwise have to occur over longerd istances along covalentp athways, reminiscent of the behavior seen for certain proteins. The simplistic pictureo ft ube-like electron transferc an de-scribe this superpositiono fd ifferent pathways including both the covalenth elical backbone, as well as noncovalent contacts, contrasting the wire-like behavior reportedm any times before for more conventional molecular bridges. The exquisite control over the molecular architecture, achievable with the configurationally stable and topologically defined 1,2-naphthylene-baseds caffolds, is of key importancef or the tube-like electron transfer behavior.O ur insights are relevant for the emerging field of multidimensional electron transfer and for possible future applications in molecular electronics.Scheme1.(a) Electron transfer (ET) through linear wires;( b) ET across the covalent backboneofah elical structure;(c) conformational flexibility complicates the assessment of the relative importanceo fc ovalent versus noncovalentlypathways;and (d) ET pathway involving noncovalent contacts in ahelical structure.Scheme2.(a) Donor-acceptor dyads synthesized and investigated in this work;and (b) space-filling modelo ft he dyad with n = 3( compound W3).

Mechanical single-molecule potentiometers with large switching factors from ortho-pentaphenylene foldamers

“…The superposition of offset π-π stacking interaction parallel to the helix axis and through-bond conjugation can endow ortho-phenylenes with multichannel charge transport in multidimensional degree 20,21 . With these merits, ortho-phenylenes have been theoretically predicted as potential candidates for molecular electronics long ago 22 , working as single-molecule solenoids, molecular springs, pressure sensors, and single-molecule potentiometers. However, there is scarcely any research that has literally applied ortho-phenylenes as molecular electronics in practice.…”

Enantioselective Synthesis of Atropisomers with Multiple Stereogenic Axes

“…Chemie Kurzaufsätze achieved efficiently.T his compelling stereodivergent synthesis of atropisomers with multiple stereogenic axes endows the corresponding oligoarenes with au nique and promising topology.I na ddition, the electron-transfer property associated with the conjugation of this unique class of helical oligo-1,2-naphthylenes with [Ru(bpy) 3 ] 2+ photosensitizer was investigated recently. [31] Later in 2019, Zhou and co-workers reported as tepwise strategy to synthesize chiral 2,3-diarylbenzoindoles 52 featuring two stereogenic axes with a1,2-arrangement in good yield and excellent stereoselectivity (Scheme 15). [32] Thec hiral phosphoric acid (CPA) VI catalyzed the formal (3+ +2) cycloaddition of 1-styrylnaphthols 49 with azonaphthalenes 50 to construct the enantiomerically enriched dihydropyrrole precursors 51 in good yield and excellent diastereo-and enantioselectivity.N ext, the oxidative aromatization with dichlorodicyanobenzene (DDQ) under mild conditions efficiently afforded the diarylbenzoindoles 52 through central-toaxial chirality conversion after the protection of phenolic hydroxyl group with p-toluene sulfonyl (Ts) group.N otably, this well-designed process was the first example of the conversion of two adjacent stereogenic centers into two ortho-stereogenic axes.…”

Catalyst Control over Twofold and Higher-Order Stereogenicity by Atroposelective Arene Formation

“…A series of oligo-1,2-naphthylenes bearing a triarylamine electron donor and a [Ru­(bpy) 3 ] 2+ electron acceptor at the termini of the oligomer was deemed suitable to differentiate pathways during photoinduced electron transfer (PET) . In previous linear wire donor–bridge–acceptor dyads with an oligo-( p -phenylene) bridge, the PET rate was distinctly impacted by the distance between the donor and acceptor moieties of the photochemical system. , In contrast, in corresponding oligo-1,2-naphthylenes 51 , which were synthesized by sequential arene-forming aldol cyclizations followed by end-group functionalization (Scheme ), an unusually weak dependence of the PET rate on the bridge length was encountered . This intriguing observation was explained by the occurrence of alternate non-covalent tubular PET pathways involving shortcuts through the oligo-1,2-naphthylene backbone by non-covalent contacts.…”