Weiying Lin

A Sensitive and Selective Fluorescent Thiol Probe in Water Based on the Conjugate 1,4‐Addition of Thiols to α,β‐Unsaturated Ketones

Compound 1 was designed and synthesized as a new fluorescent thiol probe. Probe 1 was constructed on the basis of the conjugate 1,4-addition of thiols to alpha,beta-unsaturated ketones. Notably, probe 1 has suitable water solubility, which allows the sensing assay to be performed in water. Probe 1 is highly sensitive for thiols with a 211-fold fluorescence dynamic range and a low detection limit of 9.25x10(-7) M. The major features of probe 1 also include a high selectivity for thiols over other relevant biological species, excitation and emission in the visible region, rapid functioning at pH 7.4, and a good linear relationship between the fluorescence signal and the thiol concentration. Accordingly, these desirable characteristics may render probe 1 as potentially useful for biological applications.

A Ratiometric Fluorescent Probe for Hypochlorite Based on a Deoximation Reaction

In this work, we have successfully provided a novel strategy for the rational design and synthesis of a ratiometric fluorescent probe for hypochlorite. The strategy is based on the deoximation reaction, which has not yet been used in the fluorescent hypochlorite probe design. Interestingly, the probe showed a ratiometric fluorescent response to hypochlorite with the emission intensities ratio (I(509)/I(439)) increasing from 0.28 to 2.74. Furthermore, the probe displayed high selectivity for hypochlorite over other species due to the distinct deoximation conditions. The probe developed herein represents the first ratiometric fluorescent probe for hypochlorite.

Construction of Fluorescent Probes Via Protection/Deprotection of Functional Groups: A Ratiometric Fluorescent Probe for Cu2+

Herein a ratiometric fluorescent Cu(2+) probe was rationally constructed in a straightforward manner with the concept of aldehyde group protection/deprotection. The probe showed a ratiometric fluorescent response to Cu(2+) with a large emission wavelength shift (>100 nm) and displayed high selectivity for Cu(2+) over other metal ions due to distinct deprotection conditions. In addition, a Cu(2+)-promoted dethioacetalization mechanism was proposed.

A novel ratiometric fluorescent Fe3+ sensor based on a phenanthroimidazole chromophore.

Phenanthroimidazole derivative 1 has been developed as a rare example of ratiometric fluorescent sensors for Fe(3+). Interestingly, upon treatment with Fe(3+), the sensor displayed a ratiometric fluorescent response with an enhancement of the ratios of emission intensities at 440 and 500 nm from 0.36 to 3.24. The detection range of the sensor for Fe(3+) is in the 1.0x10(-5)-1.5x10(-4) M concentration range and the detection limit is 5.26x10(-6) M. In addition, the sensor showed good selectivity to Fe(3+) with the selectivity coefficients (K(Fe3+) = S(Fe3+)/S(0) of Fe(3+) over other metal ions tested in the range of 5-68.

Double Functional Group Transformations for Fluorescent Probe Construction: A Fluorescence Turn-On Probe for Thioureas

The development of fluorescent probes has attracted continuing attention due to the simplicity and high sensitivity of fluorescence detection. Recently, analyte-mediated organic reactions have been extensively employed to design a wide variety of fluorescent probes. In many reaction-based fluorescent probes, the fluorescence properties of the dyes are regulated by a single functional group. Thus, only a single functional group transformation is involved in the analytemediated reactions for the fluorescence response (Figure 1, top). However, the development of fluorescent probes based on a single functional group transformation with high selectivity is still very challenging, since structurally and chemically related analytes may compete with the same key functional group in the probes. For instance, a fluorescent probe with an electrophilic carbonyl group is known to react with strong nucleophiles, such as Cys and CN . Consequently, the probe has poor selectivity for these distinct analytes. On the other hand, fluorescence turn-on probes may be designed based on the double functional group transformation strategy provided that the fluorescence intensity of a dye is suppressed by two different functional groups (Figure 1, bottom). Obviously, the intense fluorescence is restored only after both functional groups are transformed by the target analyte. However, if neither, or only one, functional group is transformed by other analytes, the fluorescence of the dye may remain very dim. Thus, a double functional group transformation strategy may allow the probe to show selectivity for the target analyte over other potentially competing species that can incite no, or only single, functional group transformation on the probe. This design approach, in principle, may be favorable for improvement of selectivity, as double and single functional group transformation products may have discrete emission profiles. Thioureas have been widely used as fungicides or accelerators of sprouting in dormant tubers in agriculture and as vulcanization accelerators in industry. However, the toxicity of thioureas is associated with diseases, such as dermatitis, pulmonary edema, chronic goitrogenic difficulties, and thyroid and liver tumors. Thus, it is critical to detect thioureas. To the best of our knowledge, fluorescence turn-on probes for thioureas that can operate in aqueous solution have not been previously developed. In this contribution, we report the development of the first fluorescence turn-on thiourea probe 1 (Scheme 1) by the double functional group transformation strategy. Probe 1 is composed of a coumarin dye, a carbonyl group, and a bromide group. The choice of the carbonyl and bromide groups is based on the following considerations: 1) The carbonyl group may significantly decrease the fluorescence of the coumarin dye due to the intersystem crossing from singlet (n, p*) to triplet state (p, p*). In addition, the bromide moiety is also a well-known fluorescence quencher in light of its heavy atom effect. Thus, these two fluorescence [a] Prof. W. Lin, X. Cao, L. Yuan, Y. Ding State Key Laboratory of Chemo/Biosensing and Chemometrics College of Chemistry and Chemical Engineering, Hunan University Changsha, Hunan 410082 (P.R. China) Fax: (+86) 731-88821464 E-mail : weiyinglin@hnu.cn Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201000244. Figure 1. Top: development of reaction-based fluorescence turn-on probes by the single functional group transformation approach. Bottom: development of reaction-based fluorescence turn-on probes by the double functional group transformation strategy.