Design of Redox/Radical Sensing Molecules via Nitrile Imine-Mediated Tetrazole-ene Cycloaddition (NITEC)

Paul Lederhose, Naomi L. Haworth, Komba Thomas, Steven E. Bottle, Michelle L. Coote, Christopher Barner-Kowollik, James P. Blinco

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)

Abstract

The current study introduces a novel synthetic avenue for the preparation of profluorescent nitroxides via nitrile imine-mediated tetrazole-ene cycloaddition (NITEC). The photoinduced cycloaddition was performed under metal-free, mild conditions allowing the preparation of a library of the nitroxide functionalized pyrazolines and corresponding methoxyamines. High reaction rates and full conversion were observed, with the presence of the nitroxide having no significant impact on the cycloaddition performance. The formed products were investigated with respect to their photophysical properties in order to quantify their "switch on/off" behavior. The fluorescence quenching performance is strongly dependent on the distance between the chromophore and the free radical spin as demonstrated theoretically and experimentally. Highest levels of fluorescence quenching were achieved for pyrazolines with the nitroxide directly fused to the chromophore. Importantly, the pyrazoline profluorescent nitroxides were shown to efficiently act as sensors for redox/radical processes.

Original languageEnglish
Pages (from-to)8009-8017
Number of pages9
JournalJournal of Organic Chemistry
Volume80
Issue number16
DOIs
Publication statusPublished - 21 Aug 2015
Externally publishedYes

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