Synthesis and characterization of new rhodamine dyes with large Stokes shift

摘要

Two new rhodamine dyes (Rh Q-H, Rh Q-Me) containing 1, 4-diethyl-1, 2, 3,4-tetrahydroquinoxaline as an effective electron donor are designed and synthesized. The structures of the novel compounds are confirmed by ~1H NMR, ~(13)C NMR and ESI. Due to an excited-state intramolecular charge transfer (ICT), the new dyes exhibit longer absorption (>580 nm) and emission (>640 nm) compared with the model compounds, rhodamine 101 and rhodamine 6G. The new rhodamine dyes show large Stokes shift of 40-50 nm in commonly used solvents. Notably, when measured in a mixture of H2O/EtOH solution, significant stokes shift of 65-68 nm are achieved, which is among the largest Stokes shifts ever reported for rhodamine dyes.