A copillar[5]arene derivative with different repeating units was synthesized by co-oligomerization of different alkyl ethers. Copillar[5]arene-based supramolecular polymer gel was formed by a self-inclusion complexing in acetonitrile. The supramolecular polymer gel was driven by the CH· π interactions, and presented two phases as time went on, and finally, constructed the supramolecular organic framework. Notably, the supramolecular polymer gel showed reversible gel-sol phase transitions upon heating and cooling. Meanwhile, the transparent films formed by the supramloecular gel show the potential application in the field of anti-acid rain materials.

A bilateral Schiff base is reported for the colorimetric and fluorometric dual-channel sensing of Hg²⁺ ions by taking advantage of the hydrolysis of carbon-nitrogen double bond, altering an ICT state mechanism and then Hg²⁺ ions coordinating with amino moieties of 1,5-DAN and leading to the aggregation of 1,5-DAN. Meanwhile, it formed a stable neutral complex of amino-Hg-amino. In addition, test strips based on L were fabricated, which also exhibited a good selectivity to Hg²⁺ as in solution. This work provides a novel approach for the selective recognition of mercury ions. Notably, the color changes are very significant and all the recognition processes can be observed by the naked eyes. We believe the test strips can act as a convenient and efficient Hg²⁺ test kit.

A novel optical chemical sensor L was designed and synthesized for the determination of silver ions. The sensor L was derived from 1-naphthaldehyde and 3,4,5-tris(hexadecyloxy)benzohydrazide. The sensor L shows high sensitivity and selectivity for Ag⁺ detection in comparison to other metal cations (Mg²⁺, Ca²⁺, Al³⁺, Cr³⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺) and has no significant response to other common metal cations. Upon addition of Ag⁺, the fluorescent emission of the sensor L was enhanced dramatically but other metal cations had no same response. The detection limit for Ag⁺ was 1.2×10⁻⁷ mol/L. Therefore, the sensor L is useful for Ag⁺ detection with some advantages including sensitivity, selectivity, simplicity and low-cost.

A novel copper selective sensor 2 based on hydrazide and salicylaldehyde has been designed and prepared. Sensor 2 behaves a single selectivity and sensitivity in the recognition for Cu²⁺ over other metal ions such as Fe³⁺, Hg²⁺, Ag⁺, Ca²⁺, Zn²⁺, Pb²⁺, Cd²⁺, Ni²⁺, Co²⁺, Cr³⁺ and Mg²⁺ in DMSO. The distinct color change and the rapid changement of fluorescence emission provide naked-eyes detection for Cu²⁺. The UV-vis data indicate that 1:2 stoichiometry complex is formed by sensor 2 and Cu²⁺. The association constant K_s was 3.51×10⁴ mol⁻¹·L. The detection limitation of Cu²⁺ with the sensor 2 was 2.2×10⁻⁷ mol·L⁻¹. The sensing of Cu²⁺ by this sensor was found to be reversible, with the Cu²⁺-induced color being lost upon addition of EDTA.

A series of novel tripodal colorimetric anion sensors based on hydrazone CHNNH groups have been synthesized and their recognition behavior with anionic guests has been studied. In DMSO solutions, sensors 1 and 2 show colorimetric responses for F⁻, H₂PO⁻₄ and AcO⁻, while in DMSO/H₂O (9:1, V/V) solutions, sensor 1 shows single selectivity for AcO⁻. ¹H NMR titration confirms that the tripodal sensors could bind anions through the collaboration of three hydrazone groups and anions residing in the central cavity of the sensors.

Two novel artificial tweezer receptors 1,3-phenylenedi(carbonylhydrazone) derivatives with a symmetrical structure have been synthesized. Receptor 3a [1,3-di(salicylidenehydrazinocarbonyl)benzene] for anions (F⁻, Cl⁻, Br⁻, I⁻, AcO⁻, HSO₄⁻, H₂PO₄⁻, ClO₄⁻) was investigated by UV-Vis spectroscopy in DMSO and even 85% DMSO-15% H₂O binary solutions, respectively. Remarkable color changes from colorless to yellow were observed by the naked-eye upon addition of AcO⁻, F⁻ and H₂PO₄⁻ to the solution of receptor 3a. The ¹H NMR signals indicated that the receptor 3a underwent deprotonation after the addition of an excess of fluoride anion. In particular, the anion recognition was successfully applied to CH₃COONa in 15% H₂O-85% DMSO. These findings were expected to be of significance for designing and developing novel color-based anion sensors operated in aqueous media.

Three title compounds have been designed and synthesized in high yields as novel anion receptors, which show a higher selectivity for F⁻ than other halide ions. The binding properties for fluoride ions of the receptors have been examined by UV-Vis and ¹H NMR spectroscopy, indicating that a 1:1 stoichiometry complex is formed between the receptors and fluoride ions through hydrogen bonding interactions in DMSO solution. In addition, because these receptors have more binding points, they have better binding properties for anions than the molecular tweezer receptors based on thiourea we reported last time.