Electron deficient 5-hydroxy-1,2-dihydroisoquinolin-1-ones – A new class of fluorescent dyes with large Stokes shifts

A novel class of fluorescent electron-deficient 5-hydroxyisoquinolones is proposed. The new luminophores are obtained via the reaction of stable and easily available hepta(methoxycarbonyl)cycloheptatrienyl potassium with alkylamines, anilines and acylhydrazines. The new one-pot protocol is efficient with a large scope of primary amines. The solvolysis of N-acylamino substituted 5-hydroxyisoquinolones and subsequent reactions have provided a pathway to further functionalization. Nearly all compounds have demonstrated fluorescence with considerably large the Stokes shifts (up to 6169 cm−1) except for those containing a nitro group as well as O-substituted products. In most other cases neither quantum yield nor absorption and emission maxima nor the Stokes shifts substantially depended on the substituent at the isoquinolinone ring nitrogen atom.