Rhodamine-based "turn-on" fluorescent probe with high selectivity for Fe(2+) imaging in living cells.

A rhodamine-based "turn-on" fluorescent probe 1 was synthesized with high yield. The recognizing behavior displays high selectivity of 1 toward Fe(2+) with a 2:1 complex, and 1 exhibits a stable response for Fe(2+) over a concentration range from 2 μM to 24 μM. Most importantly, probe is hardly interfered by other transition metal ions. Their fluorescent enhancement is observed in the presence of Fe(2+) because of the ring-open interactions of spirocyclic. All measurements are made in PBS buffer environments simulating biological conditions to make them suitable candidates for fluorescent labeling of biological systems. Confocal laser scanning microscopy experiments have proven that probe can be used to monitor Fe(2+) in living cells.