title: Different sensing modes of fluoride and acetate based on a calix[4]arene with 25,27-bistriazolylmethylpyrenylacetamides.
abstract: 25,27-Bis{1'-N-(1-pyrenyl)-aminocarbonylmethyl-1H-[1',2',3']tri-azolyl-4'-methoxy}-26,28-dihydroxycalix[4]arene, 4, is synthesized as a fluorescent chemosensor for the selective detection of both anions and ion pairs in MeCN. Sensor 4 uses bis-triazoles as ligands to bind a metal ion, bis-amides and bis-triazoles as the sites to recognize anions, and pyrenes as fluorophores. Among eight anions screened, chemosensor 4 showed a marked fluorescence change toward F(-), H2PO4(-) and AcO(-), but 4 responded to each anion in a distinct way. In the presence of F(-) at low concentrations, the dynamic excimer emission of compound 4 at λ(max) 482 nm was quenched, but an emission at λ(max) 472 nm appeared at large doses of F(-). A control compound 6 showed very similar red shifts in the UV-vis and excitation spectra as 4 did, and its 472 nm emission band grew as the fluoride doses increased. Thus, the growth of the 472 nm emission of 4 and 6 in the presence of excess F(-) may be because strong H-bonding interactions of amido protons with F(-) favoured the formation of pyrene dimers in the ground state with charge transfer characteristics. The addition of H2PO4(-), unlike F(-), to a solution of 4 showed an enhanced monomer emission but a decreased excimer emission (λ(max) 482 nm). Adding AcO(-) to 4 produced a systematic change from a dynamic excimer (λ(max) 482 nm) to λ(max) 472 nm but with very little change in the UV-vis spectrum. Time-resolved fluorescence measurements on compound 6 with F(-) and AcO(-) confirmed that the 472 nm emission band mainly came from static excimers for the former, but was partly from a dynamic excimer for the latter because it contained a growth component in the fluorescence decay traces. Without pre-treatment with an anion, chemosensor 4 showed recognition of only metal ions Cu(2+), Hg(2+) and Cr(3+), but it became sensitive to Ag(+) when it was pretreated with fluoride.
authors.affiliation: Department of Applied Chemistry, National Chiao-Tung University, Hsinchu, 30050, Taiwan, Republic of China. diau@mail.nctu.edu.tw wschung@nctu.edu.tw.
authors.forename: Hao-Chih
authors.initials: HC
authors.lastname: Hung
authors.forename: Yung-Yu
authors.initials: YY
authors.lastname: Chang
authors.forename: Liyang
authors.initials: L
authors.lastname: Luo
authors.forename: Chen-Hsiung
authors.initials: CH
authors.lastname: Hung
authors.forename: Eric Wei-Guang
authors.initials: EW
authors.lastname: Diau
authors.forename: Wen-Sheng
authors.initials: WS
authors.lastname: Chung
mesh_terms: D000085:Acetates / Q000032:analysis* / Q000737:chemistry*; D000577:Amides / Q000737:chemistry*; D047250:Calixarenes / Q000737:chemistry*; D002623:Chemistry Techniques, Analytical / Q000295:instrumentation*; D004579:Electron Transport; D005459:Fluorides / Q000032:analysis* / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D000085:Acetates; D000577:Amides; D010636:Phenols; C121325:calix(4)arene; D047250:Calixarenes; D005459:Fluorides