title: Colorimetric and Optical Discrimination of Halides by a Simple Chemosensor.
abstract: A thiophene-based tripodal copper(II) complex has been synthesized as a new colorimetric and optical chemosensor for naked-eye discrimination of halides in acetonitrile and an acetonitrile-water mixture. The binding interactions of the new receptor with several anions were analyzed by UV-Vis titrations, electrospray ionization mass spectrometric (ESI-MS) experiments and density functional theory (DFT) calculations. The results from UV-Vis titrations indicate that the coordinative unsaturated copper(II) complex strongly binds a halide at its vacant copper(II) centreviaa metal-ligand bond forming a 1:1 complex, exhibiting binding affinities in the order of fluoride > chloride > bromide > iodide. The interactions of the receptor with halides were further confirmed by ESI-MS, showing a distinct signal corresponding to a 1:1 complex for each halide, suggesting that the noncovalent interactions also exist in the gas phase. In addition, time-dependent DFT (TD-DFT) calculations were also carried out to understand the excited-state properties of the chemosensor complexes. A detailed analysis of the TD-DFT calculations shows a consistent red-shift in the first optically-allowed transition, consistent with the observed colorimetric experiments.
authors.affiliation: Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS 39217, USA.
authors.forename: Syed A
authors.initials: SA
authors.lastname: Haque
authors.affiliation: Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS 39217, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Bolhofner
authors.affiliation: Department of Chemical & Environmental Engineering and Materials Science & Engineering Program, University of California, Riverside, Riverside, CA 92521, USA.
authors.forename: Bryan M
authors.initials: BM
authors.lastname: Wong
authors.affiliation: Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS 39217, USA.
authors.forename: Alamgir
authors.initials: A
authors.lastname: Hossain