Opposite 6-rings Research Articles

Crystal Structure of Zeolite LTA Containing Extraframework Tungsten(VI) Ions

Tungsten(VI) has been introduced into zeolite LTA (A) by the reaction of fully dehydrated Tl-A (|Tl12|[Si12Al12O48]-A) with WCl6 (g, 7.0 × 102 Pa) at 453 K for 48 h under anhydrous conditions. The crystal structure of the product, |(WCl)0.6(Tl7Cl6)0.5Tl8.5|[Si12Al12O48]-A, was determined by single-crystal crystallography using synchrotron X-radiation. Its composition was confirmed by energy dispersive X-ray analysis. It was refined in the space group Pm3m (a = 12.061(1) A) using all data to the final error index R1 = 0.085 for the 628 unique reflections for which Fo > 4σ(Fo). WCl6 reacted with Tl+ ions in the zeolite to form WCl5+ and Tl7Cl6+. WCl5+ lies opposite 6-rings in half of the large cavities; its W6+ ion coordinates tetrahedrally to its Cl– ion and to three 6-ring oxygen atoms. The other half of the large cavities contain Tl7Cl6+; one Tl+ ion at the very center of a large cavity coordinates octahedrally to six Cl– ions, each of which bonds in turn to a Tl+ ion in an 8-ring. The remaining Tl+ ion...

Structure of a cyclohexane sorption complex of partially dehydrated, fully Mn2+-exchanged zeolite Y (FAU, Si/Al = 1.56)

The structure of a cyclohexane sorption complex of partially dehydrated, fully Mn2+-exchanged zeolite Y has been determined at 100(1) K by single-crystal synchrotron X-ray diffraction techniques. It was refined using all intensities to the final error indices R1 = 0.052 and wR2 = 0.174. Cyclohexane molecules of symmetry 3¯2/m (D3d, chair form) occupy 5.7 of the 16 12-rings per unit cell. Each cyclohexane molecule is held in place by 18 weak hydrogen bonds between its six equatorial hydrogen atoms and all 12 oxygen atoms of its 12-ring: C⋯O ca. 3.85 Å. Mn2+ ions are found at four crystallographic sites, I, I′, II′, and II. Each of the 17.7(2) Mn2+ ions per unit cell at site II (opposite 6-rings in the supercage) coordinates tetrahedrally to three framework oxygen atoms and a water molecule. The cyclohexane molecules interact neither with the Mn2+ ions nor with the water molecules.

Encapsulating Luminescent Materials in Zeolites. III. Crystal Structure and Scintillation Properties of Cs,Na-LTA Treated with Zirconium Chloride Vapor

With the purpose of developing a new zeolite scintillator, fully dehydrated Cs,Na-A was exposed to ZrCl4 (g, 3.7 × 103 Pa) at 523 K. The crystal structures of Cs,Na-A and of the product, |Zr0.14Cs5.69Na4.13Cl0.85|[Si12Al12O48]-LTA (Zr,Cs,Na,Cl-A), were determined by single-crystal crystallography using synchrotron X-radiation. The structure of Zr,Cs,Na,Cl-A was refined in the space group Pm3̅m (a = 12.230(1) Å) with all unique data to the final error index R1 = 0.069 for the 639 reflections for which Fo > 4σ(Fo). Its composition was confirmed by scanning electron microscopy energy-dispersive X-ray analysis (SEM-EDX). Octahedral ZrCl62– ions center 14% of the large cavities; each Cl– ion bonds to an 8-ring Cs+ ion. These Cs+ ions bridge between ZrCl62– ions to form a continuum with unit cell formula Cs3ZrCl6+ in the near-surface volume of the crystal. Other Cs+ ions lie opposite 6-rings in the sodalite and large cavities; Na+ ions occupy the remaining 6-rings. Upon X-irradiation, Zr,Cs,Na,Cl-A luminesces bright sky blue; the emission band is broad, ranging from 370 to 750 nm, peaking at 480 nm. The integrated intensity of the emission is ca. 16 times greater than that of anthracene, a well documented scintillator. This intense luminescence appears to result from charge transfer within the ZrCl62– ions.

Using the Thallous Ion Exchange Method to Exchange Tin into High Alumina Zeolites. 1. Crystal Structure of |Sn2+5.3Sn4+0.8Cl–1.8|[Si12Al12O48]-LTA

Sn2+ and Sn4+ ions have replaced all of the Tl+ ions in the zeolite Tl12-A (|Tl12|[Si12Al12O48]-LTA) by thallous ion exchange (TIE), a vapor phase ion exchange method: SnCl2(g) was allowed to react with Tl12-A under anhydrous conditions at 723 K for 48 h. The tin content of the product, |Sn2+5.3Sn4+0.8Cl–1.8|[Si12Al12O48]-LTA, is 32.6 wt %, much higher than previously reported for any zeolite. Its structure was determined by single-crystal crystallography at 294 K using synchrotron X-radiation (Pm3m, a = 12.075(1) A, R1 = 0.069, R2 = 0.224), and its composition was confirmed by scanning electron microscopy energy-dispersive X-ray analysis. Sn2+ is found at four crystallographic positions, Sn4+ at two, and Cl– at two. Among the 5.3 Sn2+ ions per unit cell, 2.7 (3-coordinate) lie opposite 6-rings in large cavities, 0.3 (4-coordinate) are opposite 6-rings in sodalite cavities, 1.5 are in 8-rings, and 0.7 approach a framework oxygen atom and two chloride ions in a trigonal planar manner. Among the 0.8 Sn4+ i...

Synthesis of Tellurium Sorption Complexes in Fully Dehydrated and Fully Ca2+-exchanged Zeolites A and X and their Single-crystal Structures

Single crystals of fully dehydrated and fully Ca 2+ -exchanged zeolites A (|Ca 6 |[Si 12 Al 12 O 48 ]-LTA) and X (|Ca 46 | [Si 100 Al 92 O 384 ]-FAU) were brought into contact with Te in fine pyrex capillaries at 623 K and 673 K, respectively, for 5 days. Crystal structures of Te-sorbed Ca 2+ -exchanged zeolites A and X have been determined by single-crystal X-ray diffraction techniques at 294 K in the cubic space group Pm3m (a = 12.288(2) A) and Fd 3 (a = 25.012(1) A), respectively. The crystal structures of pale red-brown |Ca 6 Te 3 |[Si 12 A 12 O 48 ]-LTA and black coloured |Ca 46 Te 8 | [Si 100 Al 92 O 384 ]-FAU have been refined to the final error indices of R 1 /wR 2 = 0.1096/0.2768 and R 1 /wR 2 = 0.1054/ 0.2979 with 204 and 282 reflections for which F o > 4σ(F o ), respectively. In the structure of |Ca 6 Te 31 |[Si 12 Al 12 O 48 ]-LTA, 6 Ca 2+ ions per unit cell were found at one crystallographic positions, on 3-fold axes equipoints of opposite 6-rings. In |Ca 46 Te 8 |[Si 100 Al 92 O 384 ]-FAU, 46 Ca 2+ ions per unit cell were found at four crystallographically distinct positions: 3 Ca 2+ ions at Ca(1) fill the 16 equivalent positions of site I, 21 Ca 2+ ions at Ca(2) fill the 32 equivalent positions of site I', 10 and 12 Ca 2+ ions at Ca(3) and Ca(4), respectively, fill the 32 equivalent positions of site II. The Te clusters are stabilized by interaction with cations and framework oxygen. In sodalite units, Te-Te distances of 2.86(10) and 2.69(4) A in zeolites A and X, respectively exhibited strong covalent properties due to their interaction with Ca 2+ ions. On the other hand, in large cavity and supercage, those of 2.99(3) and 2.76(11) A in zeolites A and X, respectively, showed ionic properties because alternative ionic interaction was formed through framework oxygen at one end and Ca 2+ cations at the other end.

Complete Redox Exchange of Indium for Tl+ in Zeolite A. Crystal Structures of Anhydrous Tl12−A and In10−A·In. Indium Appears as In2+, In+, and In0. The Clusters (In5)8+ and (In3)2+ Are Proposed

Indium has replaced all of the Tl+ ions in fully dehydrated fully Tl+-exchanged zeolite A by a solvent-free redox ion-exchange reaction with In metal at 623 K. The crystal structures of the zeolite before (Tl12Si12Al12O48: a = 12.153(4) Å, R1 = 0.054, and R2 = 0.060) and after the reaction, followed by washing with water and redehydration at 623 K (In10Si12Al12O48·In: a = 12.098(2) Å, R1 = 0.063, and R2 = 0.062), have been determined by single-crystal X-ray crystallography at 294 K using the space group Pm3m. In In10−A·In, 11 In atoms or ions/unit cell are distributed over seven crystallographically distinct positions. Seven In ions occupy 3-fold-axis equipoints: four In+ ions lie opposite 6-rings in large cavity (In(1)), and two In2+ (In(2)) and one In+ (In(3)) lie opposite 6-rings in the sodalite unit. Three In+ ions per unit cell are found at two different 8-ring positions: 1.5 on the 8-ring plane (In(4)) and 1.5 off (In(5)). Finally, one In0 atom per unit cell, probably associated with In ions, is found at two quite unusual positions: one-half of an In0 lies at the center of sodalite unit (In(6)) and the other half of the In0 is opposite a 4-ring relatively deep in the large cavity (In(7)). The crystal structure of In10−A·In is viewed as a mixture of two kinds of “unit cells,” In8−A·In and In12−A·In, each with a cationic charge of 12+. By their approach distances to framework oxygens, the ionic radii of In+ and In2+ are ca. 1.23 and 1.04 Å, respectively. The In(6) and In(7) positions lie deep within cavities where they approach only In cations. This suggests the existence of tetrahedral (In5)8+ clusters (four In2+ ions at In(2) with an In0 atom at their center at In(6), In(2)−In(6) distance = 2.754(2) Å) in half of the sodalite units (In8−A·In), and bent (In3)2+ clusters (In(1)−In(7)−In(1) angle = 148.0(9)° and In(1)−In(7) = 3.073(8) Å) in half of the large cavities (In12−A·In).

Crystal structure of cesium zeolite A prepared by complete aqueous exchange

The complete exchange of zeolite 4A with Cs + has been achieved by the reaction of a single crystal of hydrated NH 4 +-A with a modest excess of CsOH slush. Its structure was determined by X-ray crystallographic methods. Up to one additional molecule of CsOH is taken up per sodalite cavity. To avoid close Cs +-Cs + contacts through 6-rings, four Cs + ions per large cavity are found nearly opposite 4-rings rather than opposite 6-rings as is usually seen. The hydroxide ion is presumed to be between the two Cs + ions found in each sodalite cavity.