Synthesis Of Novel Anion Receptors And The Recognition Properties

Molecular recognition is the process that host molecular form binding with guest molecular selectively and produce some special function,which is an important research area in supramolecular chemistry.The anion recognition,as an important part of molecular recognition,has been given great attention from many specialists. We have synthesized some novel receptors and studied on their anion recognition properties.The major contents are as follows:1.Researches in the development of anion recognition were briefly reviewed on the following three sides:(â…°)Noncovalent interactions existed in anion coordination.(â…±) measure of anion recognition.(â…²)Design of anion receptors.2.A new series of receptors were designed and synthesized and their interactions with anions such as F^-,Cl^-,Br^-,I^-,CH₃COO^-,HSO₄^- and NO₃^- in DMSO solvent were investigated by using UV-Vis absorption spectroscopy.The results showed that the hydrogen-bonding complexes were formed between receptors and the tested anions such as CH₃COO^- and F.It was also found that the selectivity of receptors for anions could be efficiently tuned by changing the place of the substituent group at the N-phenyl moiety.The recognition mechanism and binding mode were discussed.3.Five new isophthalic aldehyde bisarylthiosemicarbazone receptors were designed and synthesized.The binding properties of the receptors with anions such as F^-,Cl^-,Br^-, I^-,CH₃COO^-,HSO₄^- and NO₃^- in DMSO were investigated by UV-Vis and ¹H NMR spectroscopy.A clear color change was observed from colorless to deep yellow upon addition of F^- and CH₃COO^- to the solution of the five receptors in DMSO.The results showed that the five receptors had a better selectivity of F^- and CH₃COO^-,but had no evident binding withCl^-,Br^-,I^-,HSO₄^- and NO₃^-.It was regular that the five receptors had different binding ability with F^- and CH₃COO^-.The UV-Vis data indicated that a 1:1 stoichiometry complex was formed between the receptors and the two anions.¹H NMR titrations and solvation effect confirmed hydrogen bonding interaction between the receptors and anions.4.A new thiosemicarbazide receptor 1:1,1' -(2,5-thiadiazole-dithioaceto)4,4' -(p-chlorine benzoyl)thiosemicarbazide was designed and synthesized.The binding properties of the receptor with anions such as F^-,Cl^-,Br^-,I^-,CH₃COO^-,HSO₄^-, NO₃^- and p-NO₂C₆H₄O^- and NO₃^- in DMSO were investigated by UV-Vis spectroscopy.Addition of host 1 to the p-NO₂C₆H₄O^- anion in DMSO resulted in decreasing absorption band at 425nm and the yellow solution of p-NO₂C₆H₄O^- anion became colorless because of the formation of host-guest complex between host 1 and p-NO₂C₆H₄O^-.The absorption spectra response was also observed in the presence of anions such as F^-,CH₃COO^- and H₂PO₄^-.The degree of change in the absorption spectra was in the order of p-NO₂C₆H₄O^-＞F^-＞CH3COO^-＞H₂PO₄^->>Cl^-,Br^-,I^-, HSO₄^-,NO₃^-.The UV-Vis spectroscopy titration experiments indicated the formation of a 1:1 stoichiometry complex between receptor 1 and anions by nonlinear curve fitting,as a result,the association constants were evaluated.Solvation effect confirmed hydrogen bonding interaction between the receptor and anions.Based on the above results,the recognition mechanism and binding mode were discussed.5.The synthesis and UV-vis and ¹H NMR spectroscopic studies of aryloxyacetyl hydrazide colorimetric sensors for anions are presented.These sensors can recognize anions through hydrogen binding even in competitive DMSO solutions,especially, the receptor 3(1,3-benzyldi(p-nitro-methylphenyloxy)acetylhydrozone)gives rise to large color change that are clearly visible to the naked eye.