Fluorescent compounds that display emission changes in response to analytes continue to be of current interest as components in sensory applications. Recently 1,3-benzazaphospholes (BAPs), a type of low valent organophosphorus molecules, have been identified as a fluorescent material. In this study, we investigate the modulation of benzazaphosphole emission in response to the addition of isolable singlet carbenes, specifically 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) and a cyclic (alkyl)(amino)carbene (2,6-diisopropylphenyl)-4,4-diethyl-2,2-dimethyl-pyrrolidin-5-ylidene (EtCAAC). In a published report, our group has demonstrated the ability of the aforementioned singlet carbenes to modulate the emission of secondary amine containing fluorophores.1 Upon addition of IPr, luminescence of the primary 2-thiophenyl-1,3-benzazaphosphole (ThBAP) is quenched due to formation of a H-bonded BAP-carbene adduct; addition of EtCAAC also leads to the formation of an adduct that exhibits a similar reduction in emission. These reactions are reversible: release of carbene from the adducts formed allows restoration of fluorescence. Emission control is accomplished through not only concentration dependent adduct formation, but also through the addition of a Lewis acid, such as borane. Solution-state dynamics, solid-state characterization, and synthetic strategies towards BAP-carbene adducts will be discussed.

Modulation of luminescence in 1,3-benzazaphospholes using isolable N-heterocyclic carbenes

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.