Molecular design of crown ethers. 19.(1) synthesis of novel disulfide- and diselenide-bridged Bis(benzo-12-crown-4)s and their Ag(+)-selective electrode properties
Two novel heteroatom-bridged bis(benzo-12-crown-4 ether)s, i.e., bis(2-nitro-4,5-(1,4,7,10-tetraoxadecamethylene)phenyl) disulfide (4) and diselenide (5), have been synthesized and characterized by elemental analysis and mass, IR, UV, and (1)H NMR spectroscopy. An X-ray crystallographic structure was obtained for 4. Ion-selective electrodes (ISE) for Ag(+), containing 4 and 5 in PVC membrane as neutral carriers, were prepared, and their selectivity coefficients for Ag(+) () were determined against other heavy metal ions, alkali and alkaline-earth metal ions, and ammonium ion using the matched potential method. These ISEs showed excellent Ag(+) selectivities, log </= -4.0, against most of the interfering cations examined, except for Hg(+) (log >/= -1.2). These values are comparable to those reported for the representative Ag(+)-selective thioethers 6 and 7, revealing that both disulfide and diselenide functionalities in 4 and 5 are equally effective Ag(+)-selective binding sites as the 1,7-dithia-4-oxa functionality in 6 and 7, irrespective of the different atom type and relative position of the sulfur/selenium donors in the ligands. Also discussed are the steric and electronic effects of the nitro groups in 4 and 5 on the Nernstian slopes obtained with the 4- and 5-based ISEs.
Liu
Y
Department of Chemistry, Nankai University, Tianjin 300071, China, Inoue Photochirogenesis Project, ERATO, JST, 4-6-3 Kamishinden, Toyonaka 565-0085, Japan, and Department of Molecular Chemistry, Osaka University, 2-1 Yamadaoka, Suita 565-087.
Zhang
HY
Chen
LX
He
XW
Wada
T
Inoue
Y