Highly selective, sensitive and biocompatible rhodamine-based isomers for Al3+detection: A comparative study

Selective detection of a metal ion with high selectivity is of great importance to understand its existence and its role in many chemical and biological processes. We report here the synthesis, characterization and Al3+ sensing properties of two rhodamine-based isomers, (E)-2-((2-(allyloxy)benzylidene)amino)ethyl)-3 ',6 '-bis(ethylamine)-2 ',7 '-dimethylspiro[isoindoline-1,9 '-xanthen]-3-one (L-2-oxy) and (E)-2-((4-(allyloxy)benzylidene)amino)ethyl)-3 ',6 '-bis(ethylamine)-2 ',7 '-dimethylspiro[isoindoline-1,9 '-xanthen]-3-one (L-4-oxy). L-2-oxyand L-4-oxy show pink coloration, significant enhancement in absorbance at 530 nm and fluorescence intensity at 553 nm in the presence of Al3+ among several cations. Quantum yield and lifetime of the probes increase in the presence of Al3+. LOD values have been determined as low as-1.0 nM for both the isomers. DFT study suggests that the cation induces opening of spirolactam ring resulting in the changes of the rhodamine dyes. Additional reason could be Chelation Enhanced Fluorescence (CHEF) effect due to the subsequent chelation of the metal ion. Be-tween two isomers, L-2-oxy displays better sensing ability towards Al3+ in terms of fluorescence enhancement, limit of detection, lifetime enhancement. Both the probes have been utilized in cell imaging studies using rat skeletal myoblast cell line (L6 cell line).

Automated summary

Selective detection of metal ions is crucial for understanding their roles in chemical and biological processes. In this study, we synthesized and characterized two rhodamine-based isomers and investigated their sensing properties towards Al3+. DFT study and cell imaging experiments demonstrated the practicality and high selectivity of these probes.