A Strategy to Design Substituted Tetraamino-Phenazine Dyes and Access to an NIR-Absorbing Benzoquinonediimine-Fused Quinoxaline

Abstract

The straightforward access to N- or C-substituted dinitro-tetraamino-phenazines ( P1–P5 ) is enabled in oxidative conditions via formation of two intermolecular C–N bonds from accessible 5-nitrobenzene-1,2,4-triamine precursors. The photophysical studies revealed green absorbing and orange-red emitting dyes, with enhanced fluorescence in the solid state. Further reduction of the nitro functions led to the isolation of a benzoquinonediimine-fused quinoxaline ( P6 ), which undergoes diprotonation to form a dicationic coupled trimethine dye absorbing beyond 800 nm.