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Highlights: [•] A tricarboyanine was first designed as a near-infared chemosensor for Cr3+. [•] The chemosensor showed ratiometric response to Cr3+ with well-resolved emissions. [•] The chemosensor exhibited a high selectivity for Cr3+ over other metal ions. [•] The chemosensor has been used in water samples and living cells successfully. [Copyright &y& Elsevier]

Abstract: A new rhodamine-based compound (1) has been synthesized and applied as an “off–on” chemosensor for Fe3+. The comparison of this method with some other fluorescence methods for Fe3+ indicates that the method can detect Fe3+ in living cells by fluorescence enhancement and color changes with high sensitivity and selectivity. The fluorescence intensity of 1 is significantly increased about 60-fold with 20 equiv of Fe3+ added. Most importantly, the fluorescence changes of the chemosensor are remarkably specific for Fe3+ in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the experiment results show that the response behavior of 1 towards Fe3+ is pH independent in neutral condition (pH 6.0–8.0) and the response of the chemosensor is fast (response time less than 2 min). In addition, the proposed chemosensor has been used for imaging of Fe3+ in living cells with satisfying results. [Copyright &y& Elsevier]