title: Fluorescein-N-Methylimidazole Conjugate as Cu(2+) Sensor in Mixed Aqueous Media Through Electron Transfer.
abstract: A new highly selective, chromogenic, and fluorogenic Cu(2+) chemosensor, fluorescein-N-methylimidazole conjugate 1, and another fluorescein-N-imidazole conjugate 2 were synthesized and investigated by UV-visible and fluorescence spectroscopy. The sensing of Cu(2+) quenches the emission band of 1 at λmax = 525 nm, with an association constant (K a = 1.0 x 10(7) M(-1)) and a stoichiometry of 1:1 in a buffered H2O: MeOH solution (4:1, pH = 7.4). The Cu(2+) detection limit for chemosensor 1 is 37 nM. The presence of the N-methyl group in 1 increased the Cu(2+) binding selectivity, resulting in a stronger binding constant and a broader pH working range (pH 5-10) in comparison to 2. The fluorescence in 1 and 2 is caused by electron transfer phenomenon from the imidazole nitrogen to fluorescein, which is readily inhibited by Cu(2+) binding.
authors.affiliation: Center of Research Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Saudi Arabia. aasifh@kfupm.edu.sa.
authors.forename: Aasif
authors.initials: A
authors.lastname: Helal
authors.affiliation: Department of Applied Chemistry, Kyungpook National University, Daegu, 702-701, Republic of Korea.
authors.forename: Hong-Seok
authors.initials: HS
authors.lastname: Kim
authors.affiliation: Center of Research Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Saudi Arabia.
authors.forename: Zain H
authors.initials: ZH
authors.lastname: Yamani
authors.affiliation: Center of Research Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Saudi Arabia.
authors.forename: M
authors.initials: M
authors.lastname: Nasiruzzaman Shaikh
keywords: Copper ion-selective; Fluorescein-N-methylimidazole electron transfer; Fluorescent chemosensor