The influence of some factors on synthesis of 5(6)-carboxy-rhodamine 110 was investigated

such as reaction time

heating mode

and nitrogen atmosphere.MALDI-TOF mass spectrometry was used for monitoring the synthesis reaction.The optimized reaction conditions are as follows.Under the protection of nitrogen

after reaction at 80℃ for 1 h the temperature is raised to 180℃ at a constant rate within 30 min.Then the reaction is maintained at the temperature for 6 h.Under the conditions the reaction is nearly completed.A little of sulfonated derivatives formed in the reaction can be purified by recrystallization.The yield is 93%.