title: Synthesis and Alkali-Metal-Ion Complexation of P-Stereogenic Diphosphacrowns.
abstract: Phosphine is conformationally stable because of the high inversion energy barrier of the phosphorus atom, which allows the phosphorus atom to become a chiral center. Thus, enantiopure P-stereogenic 12-, 15-, 18-, and 21-membered aliphatic phosphines "diphosphacrowns" were synthesized from secondary P-stereogenic bisphosphine as a chiral building block. Their complexation behaviors with alkali metal ions are investigated in comparison with benzo-18-diphosphacrown-6 and benzo-18-crown-6. 15-, 18-, and 21-Membered diphosphacrowns captured alkali metal ions to form 1:1 metal complexes. Unique guest selectivity was observed, as diphosphacrowns encapsulated smaller alkali metal ions than common crown ethers; for example, 18-membered diphosphacrowns interacted more strongly with Na(+) than K(+). The difference in guest selectivity between diphosphacrowns and common crown ethers is speculated to result from the cavity size, owing to the large phosphorus atom as well as steric hindrance around the phosphine moiety.
authors.affiliation: Department of Applied Chemistry for Environment School of Science and Technology Kwansei Gakuin University 2-1 Gakuen, Sanda Hyogo 669-1337 Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Morisaki
authors.affiliation: Department of Polymer Chemistry Graduate School of Engineering Kyoto University, Katsura, Nishikyo-ku Kyoto 615-8510 Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Kato
authors.affiliation: Department of Polymer Chemistry Graduate School of Engineering Kyoto University, Katsura, Nishikyo-ku Kyoto 615-8510 Japan.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Chujo
keywords: P-stereogenic phosphine; alkali metlas; chirality; crown ethers; enantioselectivity