Urea-based polyacetylenes as an optical sensor for fluoride ions

Nitrophenyl Thiourea-Modified Polyethylenimine Colorimetric Sensor for Sulfate, Fluorine, and Acetate

A thiourea-based colorimetric sensor incorporating polyethyleneimine (PEI) and chromophoric nitrophenyl groups was synthesized and utilized for detecting various anions. Structural characterization of the sensor was accomplished using FTIR and 1H-NMR spectroscopy. The sensor's interactions and colorimetric recognition capabilities with different anions, including CI-, Br-, I-, F-, NO3-, PF6-, AcO-, H2PO4-, PO43-, and SO42-, were investigated via visual observation and UV/vis spectroscopy. Upon adding SO42-, F-, and AcO- anions, the sensor exhibited distinct color changes from colorless to yellow and yellowish, while other anions did not induce significant color alterations. UV/vis spectroscopic titration experiments conducted in a DMSO/H2O solution (9:1 volume ratio) demonstrated the sensor's selectivity toward SO42-, F-, and AcO-. The data revealed that the formation of the main compounds and anion complexes was mediated by hydrogen bonding, leading to signal changes in the nitrophenyl thiourea-modified PEI spectrum.

Conformational and Tautomeric Control by Supramolecular Approach in Ureido-N-iso-propyl,N'-4-(3-pyridin-2-one)pyrimidine

Ureido-N-iso-propyl,N’-4-(3-pyridin-2-one)pyrimidine (1) and its 2-methoxy pyridine derivative (1Me) has been designed and prepared. The conformational equilibrium in urea moiety and tautomerism in the pyrimidine part have been investigated by variable temperature and ¹H NMR titrations as well as DFT quantum chemical calculations. The studied compounds readily associate by triple hydrogen bonding with 2-aminonaphthyridine (A) and/or 2,6-bis(acetylamino)pyridine (B). In 1, the proton is forced to 1,3-tautomeric shift upon stimuli and keeps it position, even when one of the partners in the complex was replaced by another molecule. The observed tautomerism controlled by conformational state (kinetic trapping effect) opens new possibilities in molecular sensing that are based on the fact that reverse reaction is not preferred.

A study on the synthesis and anion recognition of a chitosan-urea receptor

Chitosan-urea receptor for sensing PO₄³⁻ and F⁻ anions.

Dip in colorimetric fluoride sensing by a chemically engineered polymeric cellulose/bPEI conjugate in the solid state

A novel heterogeneous, selective dip-in sensor for fluoride has been developed by cross-linking oxidized cellulose with branched PEI functionalized with pNO₂-phenyl urea units.