Design & Synthesis Of Novel Optical Chemosensors With Schiff-base Group For Cation Recognition

The development of supramolecular chemistry intrinsiclly promoted the scientific research and practical application of supramolecular devices in molecular recognition. After the discovery and evolution of crown ester by Charles Pedersen, the exploration of supramolecular devices that used in molecular recognition has a rapid development. Especially the rapid and on-line detection of guest molecules by supramolecular optical chemosensors have the advantage of high selectivity, high sensitivity and expedience. Among the chemical toxicant and environmental protection technology, design high selectivity and high senstivity optical chemosensors for transitional metal ion have become a research upsurge. Based on the review and analysis of large numbers of literatures, we set about our work by choosing imine group and thiadiazole derivatives as recognition moiety to synthesize a series of chemosensors for sensing of metal ion. For choose those was largely inasmuch as the well delocalized imine group not only can used as a linker but also has a coordinative N atom, and the thiadiazole moiety has multiple coordination mode under a given condition. Combining with various chromophore and auxiliary recognition functional groups we design and synthesized three optical chemosensors. The selective sensing properties of the chemosensors were tested in details, which is as follows:(1) Using 4-dimethylaminobenzaldehyde and thiosemicarbazide as staring materials, we design and synthesized a chemosensor DBTT which characterize the typical supramolecular optical chemosensors. Including:the dimethylaminophenyl group as a reporter and thiadiazole group as sensing moiety and both linked by the well delocalized imine group. Experiments shown that DBTT could selectively sensing of Cu2+in methanol-2%water system with a preferable anti-interference performance. The 1NMR titration revealed that S atom, mercaptan and imine group have a strong interaction with Cu2+, and then we supposed a possible recognition mechanism. Finally, we prepared a test paper for Cu2+using DBTT, which could be used to fast detection of Cu2+in given conditions by colorimetric determination with distinctly color changing.(2) Using 4-dimethylaminobenzaldehyde and 2-Hydroxy-4-diethylaminobenz-aldehyde as staring materials we synthesized two optical chemosensors DDTP and DPTP. Both the two sensors could selectively sensing of Ag+in ethonal-2%water system. On the addition of Ag+the color of the solution changed from light yellow to vermeil, and this enable the sensing system could used for naked eye determination. The possible recognition mechanism was revealed by the corresponding model compounds coupled with FT-IR spectra and 1H-NMR titration.(3) Using 2-Hydroxy-4-diethylaminobenzaldehyde, salicylaldehyde and 4-aminoantipyrine as starting materials we synthesized two selective optical chemosensors DHDP and HDPP for Cu2+recognition. The possible structure-recognition relationships were discussed in details by corresponding model compounds and crystal structures. A further illustration of the recognition mechanism was revealed by FT-IR spectra and 1H-NMR titration. The preferable performance of the chemosensors is essential for the potential applications in environmental analysis, biosensing technics or cellar imaging.