Dariush Saberi

A new rhodamine-B carbonyl-morpholine derivative (denoted as RECM) was prepared by a two-step synthesis procedure. The employed method allowed a lactam ring development of rhodamine-B and ethylenediamine to demonstrate a facile amide bond formation. The obtained RECM was confirmed by 1H NMR, 13C NMR, and mass spectrometry analysis. RECM was formed to detect copper ion (Cu2 ) due to its problematic toxicity features in aquatic ecosystems. It showed a high selectivity toward Cu2 in comparison with some environmentally relevant alkali, alkaline earth, and transition metal cations at 50 M in acetonitrile. Moreover, non-fluorescent RECM showed fluorescence intensity and UV-Vis absorbance increases in the presence of Cu2 with high linear dependent coefficients (R2 = 0.964 and R2 = 0.982 respectively) as well as a color change from colorless to pink owing to the ring opening of the rhodamine spirolactam form. Binding capability experiments presented a clear 1:1 stoichiometry of RECM–Cu2 complex with the binding constant (Ka) as 2.25  104 M??1. The calculation of limits of detection (LOD) was 0.21 M based on the linear regression method, which is below the maximum contaminant level goal (MCLG) value of Cu2 (1.3 ppm equals to 20.46 M) in drinking water. These characteristics make the RECM a promising candidate for the real-time detection of toxic Cu2 in environmental monitoring applications