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Abstract: A new fluorescent resonance energy transfer (FRET) based fluorescent probe (compound 1) containing a dansyl unit as a donor and rhodamine 101 as an acceptor was developed to detect Fe3+ from other transition metal ions through ratiometric sensing in organic-aqueous solutions. Fe3+ induced a ring-opening reaction of the spirolactam rhodamine moiety of 1 resulting in the formation of a fluorescent derivative that can serve as the FRET acceptor. Ratiometric sensing of Fe3+ was accomplished by plotting the fluorescence intensity ratio at 605nm and 515 nm versus ferric ion concentration. The probe displayed a linear response to Fe3+ in the range of 5.5–25μM with a detection limit of 0.64μM. A 1:1 stoichiometry for the 1–Fe3+ complex was formed with an association constant of 1.74×104 M−1. The probe also exhibited a large Stokes shift (225nm) which can eliminate backscattering effects of excitation light. [Copyright &y& Elsevier]

Abstract: A new rhodamine-based derivative (1) is designed as a colorimetric and fluorescent “off–on” chemosensor for Cr3+ in aqueous solutions. Its sensing behaviors toward metal ions in neutral aqueous solutions were investigated by UV–vis absorption and fluorescence spectroscopies. Compound 1 is found to exhibit a significant increase in absorbance at 581nm and an amplified fluorescence at 600nm toward Cr3+ in a preferential, sensitive and rapid manner. Upon addition of Cr3+, the spirolactam ring (colorless and nonfluorescent) of 1 was opened to form a ring-opened amide (purple red color and fluorescent) and a 1:1 stoichiometry for the 1-Cr3+ complex was formed with an association constant of 5.75×104 M−1. The quantification of Cr3+ by 1 using a fluorescence spectroscopy method was satisfactory in the linear working range below 4μM, with a detection limit of 3.75×10–9 M for Cr3+ and good tolerance of other metal ions. The chemosensor has been used for imaging of Cr3+ in living Hela cells with satisfying results. [Copyright &y& Elsevier]

Abstract: A new chemodosimeter based on the spirolactam form of rhodamine 101 hydrazide (I) has been synthesized. This chemodosimeter is found to exhibit an irreversible colorimetric and fluorogenic response toward Cu2+ in aqueous solution in a highly selective, sensitive and rapid manner. The dominating fluorescence maximum is red-shifted to 600nm. Such a red region is reported uniquely among the rhodamine chemodosimeters on Cu2+. The colorimetric and fluorogenic response of I toward Cu2+ is proposed to be attributed to Cu2+-promoted redox hydrolysis of I. [ABSTRACT FROM AUTHOR]