Phenoxazine-based ambipolar luminescent room-temperature liquid crystals capable of being used in bioimaging applications

Abstract

A new class of phenoxazine-based luminescent liquid crystal molecules (POs) were synthesized employing the double Knoevenagel condensation of phenoxazine dialdehyde with various alkoxy-substituted phenyl acetonitrile derivatives. This new series of molecules exhibit high solubility and excellent thermal stability. The compound with six peripheral n-alkoxy chains (PO4) stabilizes a room-temperature columnar liquid crystalline phase due to efficient space–filling interactions. The synthesized molecules exhibit high luminescence intensity in both solution and solid states. The liquid crystalline molecule PO4 exhibits positive solvatochromism with HLCT behavior, demonstrating phosphorescence at 77 K. This compound was screened for bioimaging applications due to its excellent fluorescence and high biocompatibility. Among the screened compounds, PO4 was selected due to its lower crystallization tendency and superior fluorescence and it exhibited a uniform stain distribution throughout the nematode, significantly enhancing cellular visualization. The same compound, PO4, was further explored for its potential as a fluorescent probe in bioimaging by staining MCF7 cancer cells, with cellular uptake and localization studies confirming its effectiveness in targeting and visualizing cancer cells with higher fluorescence intensity.