ChemInform Abstract: Synthesis and Applications of Rhodamine Derivatives as Fluorescent Probes
ABSTRACT Rhodamine dyes are widely used as fluorescent probes owing to their high absorption coefficient and broad fluorescence in the visible region of electromagnetic spectrum, high fluorescence quantum yield and photostability. A great interest in the development of new synthetic procedures for preparation of Rhodamine derivatives has arisen in recent years because for most applications the probe must be covalently linked to another (bio)molecule or surface. In this critical review the strategies for modification of Rhodamine dyes and a discussion on the variety of applications of these new derivatives as fluorescent probes are given (108 references).
- SourceAvailable from: Ananda Rao Boddu
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- "Dual ion chemosensors are based on a single host that can independently recognize two guest species and can provide distinct spectral responses via the same or different channels; they have already emerged and have gradually become a new research focus in the field of fluorescence sensors  . A large number of rhodamine-based " turn-on " chemosensors and chemodosimeters for transition-or heavy-metal ions have been developed in recent years   . In these systems, the signals were transduced by either opening the spirolactam ring upon metal ion coordination or irreversible chemical reactions induced by metal ions. "
ABSTRACT: A rhodamine 6G-based probe bearing a carbazole unit (R6G-CB) was developed as a fluorescent chela-tion agent for Cu 2+ and a chemodosimeter for Ce 4+ in acetonitrile:aqueous (5:5, v/v) media. The R6G-CB chemosensor exhibited selectivity toward Cu 2+ ions over other metal cations by showing " off-on "-type changes in its absorption and emission spectra, which were attributed to the transformation of the non-fluorescent and colorless spirolactam derivative to the ring-opened, fluorescent, pink amide. The Cu 2+-induced chelation-enhanced fluorescence (CHEF) is associated with the spirolactam ring opening of the rhodamine unit. This R6G-CB chemosensor also showed a fast response (<1 min) to an irreversible Ce 4+-promoted oxidation reaction, responding instantaneously at room temperature with a change that is observable by the naked eye. This through-bond energy transfer (TBET)-based sensor is also highly selective and sensitive to Ce 4+. Spectroscopic analysis revealed that different structural substitution patterns of the probe resulted in different sensitivities and selectivities for specific metal ions. The optical titration, Job's plot estimation, mass spectroscopy, and Fourier transform infrared (FT-IR) results indicated that 1:2 and 1:1 complexes formed between R6G-CB and Cu 2+ and between R6G-CB and Ce 4+ , respectively. The reversibility of the R6G-CB chemosensor was verified via its spectral response to Cu 2+ and EDTA disodium salt titration experiments. All of these features make these sensors advantageous for Cu 2+ /Ce 4+ test strip applications. Due to the significant absorption intensity changes resulting from the addition of Cu 2+ and Ce 4+ ions, the novel system can act as a single-output combinational logic circuit with two chemical inputs. Finally, density functional theory (DFT) calculations were performed to gain insight into the structures and electronic properties of R6G-CB, R6G-CB-Cu 2+ complexes and R6G-CB-Ce 4+ adducts.Sensors and Actuators B Chemical 07/2015; 220:1254-1265. DOI:10.1016/j.snb.2015.07.048 · 4.29 Impact Factor
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- "Because of their excellent optical properties, many types of fluorophores have been explored for use in chemosensor materials . Among these fluorophores, rhodamines have been reported by many investigators to be a strong fluorophore for chemosensitivity because of their excellent photostabilities and photophysical properties . However, rhodamine derivatives and its ring-opening reactions have received considerable attention from organic chemists only since 1997 . "
ABSTRACT: The design and development of fluorescent chemosensors have recently been the focus of consider-able attention for the sensitive and specific detection of environmentally and biologically relevant metalions in aqueous solutions and in living cells. Herein, we report photophysical results for a 1H-pyrrole-2-carboxaldehyde-substituted rhodamine 6G derivative (RCS) that possesses specific binding affinitytoward Al3+and Cu2+at micromolar concentration levels. In an N,N-dimethylformamide (DMF) andwater (v/v = 2/8) medium, the RCS chemosensor exhibits a substantially enhanced absorbance inten-sity at 532 nm and a color change from colorless to pink for Cu2+; it also exhibits significant “off–on”fluorescence at 557 nm, accompanied by a color change from colorless to fluorescent-yellow upon bind-ing to Al3+. The RCS sensor exhibits extremely high fluorescence enhancement upon complexation withAl3+, and it can be used as a “naked eye” sensor. Through fluorescence titration at 557 nm, we confirmedthat RCS exhibits a fluorescence response with a remarkable enhancement in emission intensity resultingfrom the complexation between RCS and Al3+, whereas no emission appeared in the case of competitivemetal ions (Cu2+, Al3+, Li+, Na+, K+, Cs+, Mg2+, Ca2+, Fe2+, Co2+, Ag+, Zn2+, Cd2+, Hg2+and Pb2+) in a DMF andwater (v/v = 2/8) solution. The reversible ring-opening mechanism of the rhodamine spirolactam inducedby Al3+/Cu2+binding and the 1:1 stoichiometric structure between RCS and Al3+were adequately sup-ported by Job-plot evaluation, optical titration and FT-IR analysis. The lowest detection limit for Al3+is3.20 × 106M−1in a DMF and water (v/v = 2/8) solution. Al3+-induced chelation-enhanced fluorescence(CHEF) is associated with spirolactam ring opening of the rhodamine unit. Finally, RCS was successfullyapplied for the bio-imaging of Al3+in living HeLa cells and for fluorescence imaging of a microfluidicsystem.Sensors and Actuators B Chemical 01/2015; 210:173-182. DOI:10.1016/j.snb.2014.12.100 · 4.29 Impact Factor
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- "In contrast with the classic rhodamines (such as rhodamine B, rhodamine 6G, and rhodamine 101), a large Stokes shift was detected in common solvents for recently synthesized rhodamines , compatible with the existence of a deactivation mechanism of the first excited singlet state involving intramolecular charge transfer (ICT) interactions. It is also well known that rhodamine dyes may act as fluorescence on-off switching mechanism (the o-carboxylic acid group of rhodamine dyes can undergo intramolecular cyclization turning the open form into a spirocyclic one   , which is non-fluorescent due to the interruption of the π-electron system in the dye's chromophores). "
ABSTRACT: Two new compounds derivatives of the "rhodamine-like" heterocyclic system 6-(N,N-diethylamino)-1,2,3,4-tetrahydroxanthylium were synthesized, bearing an aniline fragment in the conjugation chain. Their spectral-luminescent properties were investigated; fluorescence quantum yields and lifetimes were obtained for each dye in three different solvents. Dye 3a presents the highest fluorescence quantum yield in dichloromethane (ΦF = 0.60). In contrast with classic rhodamines, a large Stokes shift was detected, compatible with a mechanism of deactivation involving twisted intramolecular charge transfer interactions. These rhodamine-like compounds exhibit very low quantum yield of singlet oxygen formation (ΦΔ = 0.07 for 3a), similar to what is observed for other hemicyanines. Triplet-triplet absorption spectra were also obtained, as well as the quantum yield of intersystem crossing (ΦT = 0.10 for 3a). Photostability was evaluated under visible and laser irradiation and dye 3a proved to be the most stable one, making it a good candidate to be used as imaging agent.Dyes and Pigments 01/2015; 112:73-80. DOI:10.1016/j.dyepig.2014.06.021 · 3.97 Impact Factor