title: Syntheses and structures of uranyl ethylenediphosphonates: from layers to elliptical nanochannels.
abstract: A family of uranium diphosphonates have been hydrothermally synthesized through the reaction of ethylenediphosphonic acid (EDP, H4L) and uranyl nitrate/zinc uranyl acetate in the presence of organic templates, such as tetraethyl ammonium (NEt4(+)), 4,4'-bipyridine (bipy), and 1,10-phenanthroline (phen). The UO2(2+) in UO2(H2O)(H2L)(EDP-U1) is equatorially five-coordinated by four phosphonate groups and one aqua ligand, forming a pentagonal bipyramid. Each EDP ligand is doubly protonated and chelates three UO2(2+), resulting in a layered structure. Compounds (NEt4)2(UO2)3(HL)2(H2L)·4H2O (EDP-U2) and (H2bipy)UO2L (EDP-U3) have the same layered structure in which NEt4(+) and protonated bipy fill in the uranyl-phosphonate interlayers, respectively, and play a role to balance the negative charges. Different from that in EDP-U1, the UO2(2+) exists in the form of a UO6 tetragonal bipyramid and is surrounded by four different EDP ligands in EDP-U2 and EDP-U3. (Hphen)2(UO2)2(H2L)3 (EDP-U4) features a three-dimensional framework structure with large elliptical channels along the c axis (1.3 × 1.1 nm(2)). Monoprotonated phen molecules fill in these channels and hold together through strong π···π interactions. All of the four compounds have been characterized by IR and photoluminescent spectroscopy. Their characteristic emissions have been attributed as transition properties of uranyl cations. The ion-exchange study indicates that [Co(en)3](3+) could partially replace the protonated phen molecules.
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun, Jilin 130022, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Tian
authors.forename: Weiting
authors.initials: W
authors.lastname: Yang
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.forename: Song
authors.initials: S
authors.lastname: Dang
authors.forename: Qing-Jiang
authors.initials: QJ
authors.lastname: Pan
authors.forename: Zhong-Ming
authors.initials: ZM
authors.lastname: Sun