Synthesis Of Novel Schiff Receptors And Their Anion Recognition Properties

Molecular recognition is the process that host molecular form binding with guestmolecular selectively and produce some special function, which is an importantresearch area in supramolecular chemistry. The development of anion coordination chemistryis delayed compared with neutral moleculars and cations. It is therefore necessary to constructnovel anion receptors. The anion recognition, as an important part of molecularrecognition, has been given great attention from many specialists. A series ofcolorimetric fluoride ion receptors bearing phenolic hydroxyl and Schiff base groupswere synthesized. The major contents are as follows:1. Researches in the development of anion recognition were briefly reviewed,Which contain the following topics: (i) the principle of molecular recognition, thesignificane of anion recognition, the structural characteristics of anions impact onreceptor design; (ii) the development of anion recognition properties thioureareceptors; (iii) the development of anion recognition properties hydrazone receptors;(â…³) the development of anion recognition properties mercapto triazole receptors; (â…´)the development of anion recognition properties in water-containing media.2. A series of colorimetric fluoride ion receptors (3a³c) bearing azo-phenolichydroxyl and Schiff base groups were synthesized. In CH₃CN solutions, sensors(3a³c) showed colorimetric single selectivity for F^-. An easy-to-prepare test paperbased on 3a was developed, which could colorimetricly detect fluoride ionconveniently. ¹H NMR titrations and salvation effect confirm hydrogen bondinginteraction between the receptors and anions. 3a, 3b, 3c showed high sensitivity andselectivity toward F^- over competing anions, Cl^-+Br^-+I^-+F^- gave absorption changessimilar to those of single F^- experiment.3. A new and simple colorimetric sensor with high selectivity for acetate ion basedon 3-(4-nitrophenyl)-4-amino-5-mercapto-1,2,4-triazole receptor B3 has beensynthesized. The selectively binding ability of receptor B3 to acetate ion over otheranions tested was demonstrated by UV-vis absorption spectroscopy in DMSO. Inaddition, in aqueous solutions (DMSO/H₂O 7:3 (v/v)), it showed colorimetric singleselectivity for Ac-. From 1H NMR titration experiment in DMSO-d6, which suggested that sensor B3 perhaps underwent a deprotonation process.4. Series of colorimetric fluoride ion receptors (J1^J3) bearing hydrazone groupswere synthesized. Sensors J2^J3 showed colorimetricsingle selectivity for F^-,CH₃COO^-, H₂PO₄^- dramatic color changes were observed. Indicated that the phenolO-H group plays a critical role in the anion-recognition process. From UV-vistitration experiment, it turned out that in DMSO solutions, J2 reacted with F^- andformed 1:1 complexes, by nonlinear leastsquares fitting.5. Series of colorimetric receptors (A^B) bearing triazole and -CH=N- weresynthesized. B showed colorimetricsingle selectivity for F^-, CH₃COO^-, H₂PO₄^-,dramatic color changes were observed. From UV-vis titration experiment, it turnedout that in DMSO solutions, B reacted with F^-, CH₃COO^- and formed 1:1 complexes,by nonlinear leastsquares fitting.