A unique rhodamine-based 'off-on' molecular spy for selective detection of trivalent aluminum and chromium ions: Synthesis, crystal structure and spectroscopic properties along with living cell imaging

The well known rhodamine framework offers an ideal model for the development of fluorescence enhanced chemosensors. Herein, a novel and simple molecule chemosensor, (E)-2-((benzo[d][1,3]dioxol-4-ylmethylene)amino)-3′,6′-bis(diethylamino)spiro[isoindoline-1,9′-xanthen]-3-one (L), has been designed by combining a rhodamine B hydrazide and a benzo[d][1,3]dioxole-4-carbaldehyde in a single molecule to prove the selectivity and sensitivity for Al³⁺and Cr³⁺in a dual-channel mode (fluorescence emission and UV-Vis). The signal transduction occurred by the increase of conjugation in the ring-open form than in the ring-closed form. Furthermore, the chemosensor L could also be used as an imaging probe without cytotoxicity for uptake and detection of Al³⁺ion in HeLa cells.