An N-linked disalicylaldehyde together with its caesium ion and dichloromethane sensing performances: 'dual key & lock' LMCT-enhanced fluorescence strategy.

The development of inexpensive, selective and rapid-response chemosensors for detecting Cs+ in waste water is highly desirable in the nuclear power industry. Here we demonstrate an efficient Cs+ optical sensor based on the N-linked disalicylaldehyde H2Qj with excited state intramolecular proton transfer (ESIPT), and it will transform into the ligand-to-metal charge transfer (LMCT) process in the presence of Cs+, resulting in dramatically enhanced fluorescence together with a distinct change of color from light-green to green-yellow. Simultaneously, it is found that CH2Cl2 can serve as the quencher of LMCT-enhanced fluorescence, thus enabling selective CH2Cl2 detection in a turn-off fluorescence approach. Further detailed studies reveal that both Cs+ and CH2Cl2 sensing processes are rapid within 60 seconds. The corresponding limit of detection (LOD) values for sensing Cs+ and CH2Cl2 are as low as 0.37 mM and 0.37%. Moreover, it was also verified that Cs+ sensing is applicable in the range of pH = 7-11 and the reversibility of sensor H2Qj can be easily achieved by modulating pH values, and H2Qj is also assessed for its Cs+ sensing performces in real water samples. This H2Qj-Cs sensing system must provide a valuable reference for further Cs+ sensors.

An excellent colorimetric and "turn off" fluorescent probe for tetrahydrofuran based on a luminescent macrocyclic samarium(iii) complex.

In this paper we report a novel probe based on a luminescent 23-membered [1 + 1] Schiff-base macrocyclic mononuclear Sm(iii) complex Sm-2e, originating from the dialdehyde H2Qe and 1,2-bis(2-aminoethoxy)ethane precursors, which is synthesized by the Sm(iii) ion template method. X-ray structural analyses confirm that each ten-coordinate Sm(iii) center with the coordination geometry of a distorted bicapped square antiprism is fully encapsulated by a flexible macrocyclic ligand H2L2e to form a "lasso-type" architecture, and this architecture could enable efficient energy transfer in various solvents confirmed by long lifetimes (33.5-65.2 µs) and high quantum yields (0.23-0.76%) of the Sm(iii) ion. Simultaneously, complex Sm-2e could serve as a probe for sensing organic solvents. Particularly, this complex probe Sm-2e exhibits a highly selective, rapid and sensitive response to tetrahydrofuran (THF), which is easily distinguished by a large absorption shift, even visible to the naked eye, and complete fluorescence quenching. Moreover, the limit of detection for THF is about 0.20% determined by titration experiments, and good selectivity for THF could still be realized in mixture solvents. Consequently, this colorimetric and "turn off" fluorescent probe Sm-2e could be a valuable candidate as a sensor material for sensing THF which has been rarely reported.

Combination of imine bond and samarium emitter enables turn-off fluorescence detection of hydrazine in vapor and water samples.

The development of convenient and efficient fluorescence techniques is of great significance for selective detection and precise determination of biotoxic N2H4 in human health and environmental sciences. By the pre-organization-assisted template synthesis, disclosed here is a luminescent Sm(III) macrocycle-based probe Sm-2m bearing dynamic imine bonds as recognition moieties which provides the selective and ratiometric turn-off fluorescence sensing for N2H4 over various amine species based on the N2H4-induced structure transformation. This fluorescent sensing process finished within 20 min shows the low limit of detection (0.18 µM, 7.2 ppb) and wide linear sensing range (0-60.0 µM). Furthermore, probe Sm-2m is also be used to quantitatively determine N2H4 in vapor gas and water samples through fluorescence color changes, which are evaluated by the Sm-2m-impregnated test paper strips and RGB value outputs. Finally, our proposed smartphone-based analytical method gives satisfactory N2H4 detection results. It is thus believed that this work can shed some lights on development of optical probes and detection techniques for N2H4, even other hazardous chemicals.

Imine bond transformation of a dynamic Sm(III) macrocycle-based chemosensor: The indirect approach for detecting cyanuric chloride.

Herein, we report our strategy to develop the efficient chemosensor and real-time monitoring technique for cyanuric chloride (TCT) detection. A luminescent macrocyclic mononuclear Sm(III) complex Sm-2k bearing with two dynamic imine bonds has been constructed via the template synthesis between dialdehyde H2Qk and matched diamine 1,2-bis(2-aminoethoxy)ethane. Sensing experiments reveal that complex Sm-2k exhibits the turn-off fluorescent and colorimetric response for TCT in CH3OH. It is especially encouraging that this optical sensing process is not only rapid within 60 s but also high-efficient in the presence of TCT analogues as well as sensitive with the low limit of detection (LOD, 1.74 µM) and wide linear sensing range. Mechanism studies demonstrate that TCT sensing is mainly based on the imine bond transformation of probe Sm-2k, which is due to the increased acidity induced by TCT. Meanwhile, a smartphone-based analytical method was developed to make complex Sm-2k accessible for the real-time TCT detection by RGB value outputs. It is believed that this work can shed some constructive lights on design of chemosensors and convenient detection technique for highly reactive analytes.

Luminescent Sm(III) complex bearing dynamic imine bonds as a multi-responsive fluorescent sensor for F- and PO43- anions together with Zn2+ cation in water samples.

We have designed and synthesized a new luminescent mononuclear samarium (III) complex Sm-2h based on the [1 + 1] Schiff-base macrocycle H2L2h, derived from the cyclocondensation reaction between dialdehyde and diamine precursors, and its exact architecture is determined to be [Sm(HL2h) (NO3)2]. The sensing ability of complex Sm-2h is carefully evaluated for various common inorganic ions in solution. It is shown that complex Sm-2h is a multi-responsive fluorimetric sensor with high selectivity for F- and PO43- anions together with Zn2+ cation. The sensing process is rapid within 60 s for F- and PO43- ions and 300 s for Zn2+ ion. Further detailed responsive investigations suggest that its sensing behavior has excellent linear relationship between the fluorescence intensity (or absorption value) and ion concentration. The limit of detection (LOD) for sensing F-, PO43- and Zn2+ ions are as low as 2.61 µM (2.94 µM), 1.92 µM (1.64 µM) and 5.67 µM (3.53 µM), respectively, verified by fluorimetric (or colorimetric) titration experiments. ESI mass spectra prove that these efficient detections originate from the structure collapse of sensor Sm-2h because of the ion-induced imine bond breakage. Moreover, sensor Sm-2h shows excellent sensing performances for F-, PO43- and Zn2+ ions in real water samples, and we also have developed a convenient method to detect these three ions by use of the sensor impregnated test paper strips, providing rapid and distinguishable fluorimetric color changes. Therefore, the macrocyclic Sm(III) complex Sm-2h could be regarded as a valuable candidate for monitoring F-, PO43- and Zn2+ ions in practical applications.

Series of Highly Luminescent Macrocyclic Sm(III) Complexes: Functional Group Modifications Together with Luminescence Performances in Solid-State, Solution, and Doped Poly(methylmethacrylate) Film.

Here, we report our trials to regulate the luminescence performance of the macrocyclic samarium(III) complex and prepare four excellent luminescent Sm(III) complex-doped poly(methylmethacrylate) (PMMA) composites. Four 23-membered [1 + 1] Schiff-base macrocyclic mononuclear Sm(III) complexes, Sm-2 a -Sm-2 d , originating from dialdehydes with different pendant arms and 1,2-bis(2-aminoethoxy)ethane, have been constructed by the template method. Crystal structures reveal that every Sm(III) ion with the coordination geometry of a distorted bicapped square antiprism is capsulated by the macrocyclic cavity environment forming the "lasso-type" protection. Relative photophysical properties of macrocyclic Sm(III) complexes are carefully investigated in solid-state, methanol solution, and doped PMMA film, and all these show characteristic emissions of the Sm(III) ion associated with satisfactory lifetimes and quantum yields in all media, which could be comparable to reported outstanding examples. Especially, the luminescence performance for this type of Sm(III) complex could be regulated in the solid state by the use of different functional groups in the pendant arm while it is not achieved in solution and the doped PMMA composite. High emitting and air-stable plastic materials could be obtained when these Sm(III) complexes are doped in PMMA with 0.1 wt % mixing ratio, and the corresponding maximum lifetime and quantum yield are 61.2 µs and 0.63% in the case of complex Sm-2 a , respectively. We believe that these highly luminescent "lasso-type" Sm(III) complexes and doped PMMA composites are valuable references in the design of luminescent lanthanide(III) hybrid materials.