Pyrazolone as a recognition site: Rhodamine 6G‐based fluorescent probe for the selective recognition of Fe3+ in acetonitrile–aqueous solution

Two novel Rhodamine–pyrazolone‐based colorimetric off–on fluorescent chemosensors for Fe³⁺ ions were designed and synthesized using pyrazolone as the recognition moiety and Rhodamine 6G as the signalling moiety. The photophysical properties and Fe³⁺‐binding properties of sensors L¹ and L² in acetonitrile–aqueous solution were also investigated. Both sensors successfully exhibit a remarkably ‘turn‐on’ response, toward Fe³⁺, which was attributed to 1: 2 complex formation between Fe³⁺ and L¹/L². The fluorescent and colorimetric response to Fe³⁺ can be detected by the naked eye, which provides a facile method for the visual detection of Fe³⁺. Copyright © 2014 John Wiley & Sons, Ltd.