An unusual luminescent inorganic oxide, Sr2CeO4, was identified by parallel screening techniques from within a combinatorial library of more than 25,000 members prepared by automated thin-film synthesis. A bulk sample of single-phase Sr2CeO4 was prepared, and its structure, determined from powder x-ray diffraction data, reveals one-dimensional chains of edge-sharing CeO6 octahedra, with two terminal oxygen atoms per cerium center, that are isolated from one another by Sr2+ cations. The emission maximum at 485 nanometers appears blue-white and has a quantum yield of 0.48 +/- 0.02. The excited-state lifetime, electron spin resonance, magnetic susceptibility, and structural data all suggest that luminescence originates from a ligand-to-metal Ce4+ charge transfer.

A sodium titanosilicate of ideal composition Na2TÍ203Si04'2H20 was synthesized hydrothermally in highly alkaline media. Its crystal structure was solved from X-ray powder data by ab initio methods. The compound is tetragonal, a = 7.8082(2), c = 11.9735(4) Á, space group PA^Jmcm, Z -A. The titanium atoms occur in clusters of four grouped about the 42 axis and are octahedrally coordinated by oxygen atoms. The silicate groups serve to link the titanium clusters into groups of four arranged in a square of about 7.8 Á in length. These squares are linked to similar ones in the c direction by sharing corners to form a framework which encloses a tunnel. Half the Na+ ions are situated in the framework coordinated by silicate oxygen atoms and water molecules. The remaining sodiums are present in the cavity, but evidence indicates that some of them are replaced by protons. The composition is then closer to Nai.eiHo.se^OsSiCUfi.S^O. The sodium ions within the tunnels are exchangeable. Exhaustive exchange with CsNOs yielded a Cs+ phase of composition NaiAgCso^Ho.si^OsSiCh-^O whose structure was revealed from application of Rietveld methods to X-ray powder data.

A titanosilicate with the ideal formula, Na2Ti2O3SiO4·2H2O, containing unidimensional channels, was synthesized hydrothermally and converted to the hydrogen form by acid treatment. The hydrogen form was partially ion exchanged by sodium ions to obtain a 50% sodium ion exchanged phase. The crystals of the sodium phase, NaHTi2O3SiO4·2H2O, retain the symmetry and unit cell parameters of the parent disodium compound, space group P42/mcm, a = b = 7.832(1) Å, c = 11.945(2) Å, and Z = 4. The sodium ions are located on the ac faces of the crystal while the water molecules occupy the channels. Ion exchange of the acid form by potassium ions leads to a phase with a maximum potassium to proton ratio of about 2. In the acid, H2Ti2O3SiO4·1.5H2O, and potassium phases, K0.5H1.5Ti2O3SiO4·1.5H2O and K1.38H0.62Ti2O3SiO4·H2O, the a and b axes are doubled while the c-axis dimension is retained. These doubled dimensions were transformed to a primitive tetragonal cell which has a volume twice that of the parent sodium form. The crystals belong to the space group P42/mbc with a = 11.039(1) Å, c = 11.886(1) Å for the acid phase, a = 11.015(1) Å, c = 12.017(1) Å for the K1.38H0.62 phase, and a = 11.0604(3) Å, c = 11.9088(3) Å for the K0.5H1.5 phase. The number of molecules in the unit cell in these three cases is 8. In the acid form, the channels are occupied by the water molecules, which are involved in hydrogen bonding among themselves as well as with the framework oxygens. In the K0.5H1.5 phase, all the K+ ions are in the center of the tunnel. For the K1.38H0.62 phase, about 35% of the total potassium ions are located at the center of the channel and are bonded to the silicate oxygens. The remaining ions are found near the framework which is close to the positions of the sodium ions of the ac faces in the parent compound. These ions are bonded to both the framework and water oxygen atoms. The titanium atoms in all the phases are octahedrally coordinated, and they are grouped as clusters of four. These clusters are linked by the silicate groups along the a and b directions and by Ti−O−Ti bonds along the c directions. This structural data provide a basis for explaining the observed ion exchange behavior and ion selectivity.

A highly crystalline sample of y-zirconium phosphate Zr( PO, ) ( H2PO,)-2H,O has been prepared by hydrothermal methods and its structure solved by X-ray powder diffractometry: monoclinic, space group P2,, a = 5.3825( 2), b = 6.6337(1), c = 12.4102(4) A, p = 98.687(2)" and Z = 2. The final agreement factors are: R,, = 0.105, R, = 0.079 and R, = 0.041. In the structure the metal atoms and one of the phosphate groups are located nearly in a plane. The octahedral co-ordination of the metal atom is completed by four oxygen atoms of the phosphate group and two oxygen atoms of the dihydrogenphosphate group. The remaining two oxygens of the dihydrogenphosphate group bind to protons and project into the interlayer space. These hydroxyl groups are hydrogen bonded to the water molecules. The water molecules reside in the pockets of these hydroxyl groups and are hydrogen bonded to each other to form a zigzag chain along the b axis.Clearfield and his co-workers first prepared layered zirconium phosphate compounds with compositions Zr(HPO,),-H,O (a-ZrP) and Zr(PO4)(H,PO4).2H,O (y-ZrP)., The structure of a-ZrP was solved by single-crystal methods 3,4 while only structural models have been reported so far, for y-ZrP. The earliest model was based on X-ray and electron diffraction data from which Yamanaka and Tanaka deduced that the structure of y-ZrP is related to that of the a phase but with more densely packed metal phosphate groups in the layers. However, Clayden utilized 31P magic angle spinning (MAS) NMR data to show that y-ZrP contains equal amounts of phosphate and dihydrogenphosphate groups whereas a-ZrP contains only monohydrogenphosphate species. Subsequently, Christensen et al.' investigated the structure of the isostructural titanium analogue, Ti(P04)(H,P04)~2H,0 (y-Tip) and derived a model for the arrangement of the layers in the structure which is consistent with the NMR results. The model was refined in two possible space groups and also they were not able to locate the water molecules in the lattice. Recently we have determined the structure of the ammonium salt of y-ZrP which confirmed the above model for y-Tip. In the meantime we were able to obtain a highly crystalline sample of the parent y-ZrP the structure of which is reported in this paper.

Covalently pillared layered metal phosphonate compounds were prepared by the reaction of divalent metal salts with alkylenebis(phosphonic acids). Cu(II) yields compounds Cu2[(O3PC2H4PO3)(H2O)2] (1) and Cu2[(O3PC3H6PO3)(H2O)2]·H2O (2) when copper sulfate was reacted with ethylenebis(phosphonic acid) and propylenebis(phosphonic acid), respectively. The corresponding bis(phosphonates) obtained for the reaction with zinc chloride are Zn2[(O3PC2H4PO3)(H2O)2] (3) and Zn2[(O3PC3H6PO3)] (4). The structures of these four compounds were determined ab initio from their X-ray powder diffraction data and refined by Rietveld methods. Crystal data for compound 1:  space group P21/c, a = 8.0756(1) Å, b = 7.5872(1) Å, c = 7.4100(1) Å, β = 116.319(1)°, Z = 2. Crystal data for compound 2:  space group Pnc2, a = 4.3276(2) Å, b = 17.3181(8) Å c = 6.7624(3) Å, Z = 2. Crystal data for compound 3:  space group P21/n, a = 5.6861(8) Å, b = 15.230(2) Å, c = 4.7923(6) Å, β = 91.936(2)°. Crystal data for compound 4:  space group Pna21, a = 8.4886(6) Å, b = 5.2720(4) Å, c = 18.865(1) Å, Z = 4. The metal−oxygen bridging interactions form two-dimensional layers in all four compounds. The layers are connected to each other by the alkylene groups leading to three-dimensional structures. In the copper compounds the metal atoms are five coordinate where four of the binding sites are from the phosphonate oxygens and one from the water oxygen. The coordination geometry of the copper atoms in compounds 1 and 2 may be described as distorted square-pyramidal, but the distortion is severe in the case of compound 2. The zinc atoms in zinc ethylenebis(phosphonate) have distorted octahedral geometry. The phosphonate oxygens provide five binding sites for the metal through chelation and bridging while the water oxygen occupies the sixth coordination site. The metal atoms in compound 4, on the other hand, are tetrahedrally coordinated by the phosphonate oxygens. Unlike compounds 1−3, this compound does not contain any water molecules. The interlamellar separation is 7.2 and 7.6 Å for copper ethylenebis(phosphonate) and zinc ethylenebis(phosphonate), respectively. The difference in the layer separation, however, is significant in the propylenebis(phosphonates). For copper and zinc compounds the values are 8.65 and 9.4 Å, respectively. The layer-connecting alkyl chains create open spaces whose sizes are determined by the length of the chain. Thus, a new class of pillared materials with definable cavity sizes may be prepared.