Selective and sensitive morpholine-type rhodamine B-based colorimetric and fluorescent chemosensor for Fe(III) and Fe(II)

[Display omitted] •Rhodamine B derivatives bearing a morpholine-type 6-membered ring were synthesized.•Fluorescence sensitivities for metal ions, e.g., Fe2+ and Fe3+, were investigated.•Rh-OS, Rh-OO, and Rh-SO exhibited high sensitivity to Fe2+ and Fe3+.•Job’s plot indicated the formation of a 1:1 (ligand:metal) complex.•2D and 3D photoluminescence imaging was used for selection of Fe2+ and Fe3+. The development of chemosensor materials is crucial for the early detection of hazardous materials, such as heavy metal ions and infectious viruses. In this study, three rhodamine B (RhB) derivatives (referred to as Rh-OS, Rh-OO, and Rh-SO) bearing a morpholine-type 6-membered ring as colorimetric, fluorescent sensors were synthesized, and fluorescence responses to various metal ions (Fe3+, Fe2+, Pb2+, Cr6+, Ce2+, Mn2+, Cd2+, Hg2+, K+, Na+, Mg2+, Li+, Ca2+, As3+, Co2+, Cu2+, Ni2+, and Zn2+) were investigated. Rh-OS, Rh-OO, and Rh-SO exhibited high sensitivity to Fe2+ and Fe3+, with the formation of a 1:1 (ligand: metal) complex, as evidenced by the UV–vis absorption and photoluminescence spectra. Luminescence turn-on was explained by the transfer of resonance energy from the morpholine-type moiety to the RhB framework. In addition, the selectivity of Fe3+ and Fe2+ was evaluated by 2D and 3D photoluminescence imaging.