Olefin–Borane Interactions in Donor–π–Acceptor Fluorophores that Undergo Frustrated‐Lewis‐Pair‐Type Reactions. (29th August 2022)

• Record Type: Journal Article
• Authors: Oshimizu, Ryo; Ando, Naoki; Yamaguchi, Shigehiro
• Is Part Of: Angewandte Chemie. Volume 134:Number 41(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-08-29
• Subjects: Boron -- Fluorophores -- Frustrated Lewis Pair -- Olefin–Borane Interactions -- Temperature Response; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202209394
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: Olefin–borane π‐complexes have been postulated as intermediates for the addition of frustrated Lewis pairs (FLP) to olefins. In the present study, we have employed this weak interaction to modulate the electronic properties of boron‐based π‐electron materials. A series of donor–π–acceptor (D–π–A) fluorophores that contain an alkenyl‐bridged diarylboryl group is synthesized. A crystallographic analysis revealed that the olefin and boron moieties are held in close proximity. Upon addition of a Lewis base to a solution of these D–π–A fluorophores, an FLP‐type addition occurs with concurrent significant changes in the absorption and emission properties. The FLP‐type reaction shifts the reaction site from the Lewis‐acidic boron atom to a carbocationic center, and thereby even facilitates a reaction with bulky Lewis bases. For example, a tricyclohexylphosphine adduct thus generated exhibits temperature‐dependent reversible dissociation/association behavior. These results provide a design strategy for stimuli‐responsive emissive boron‐based materials. Abstract : Olefin–borane interaction can be used to modulate the electron‐accepting ability of boron‐containing π‐electron materials. Donor–π–acceptor fluorophores with alkenyl‐bridged diarylboryl groups exhibit response even to a bulky Lewis base through a frustrated Lewis pairs (FLP)‐type addition. Reversible association/dissociation behavior of the adduct is observed in response to temperature over a range above ambient temperature.