Lavender violet, blue and pink: A new type of benzo[a]phenoxazine-based dipolar, red-emitting dyes

Abstract

A new type of the red-emitting benzo[a]phenoxazine-based dyes, dipolar analogues of Meldola's Blue, are synthesized by condensation of p-nitrosoanilines or p-nitrosophenol with 7-(alkylamino)naphthalen-2-ol in good yields. Their photophysical properties are characterized by the donor substituents introduced, offering dyes of lavender violet, blue, and pink colors. These dyes exhibit high absorptivity, marginal-to-good optical brightness, good photostability, and show large Stokes shifts in aqueous solution. One of the dyes emits bright red fluorescence inside cells, as observed by confocal laser scanning microscopy (CLSM). The new dyes thus have potential to be used for staining purposes including cellular imaging. (C) 2017 Elsevier Ltd. All rights reserved.