SINGLE CRYSTAL STRUCTURE OF ZEOLITE A (LTA) CONTAINING AG4CL4 NANOCLUSTERS AND REDUCED 1,3,5-TRIPYRYLIUM DIMERS WITH REMARKABLY SHORT 2.43 ANGSTROM INTERPLANAR SPACINGS

Abstract

A single crystal of Ag-12-A (zeolite LTA) was prepared by the dynamic ion-exchange of Na-12-A with aqueous 0.05 M AgNO3. It was washed with CH3OH and allowed to react with a stream of 0.05 M KCl in CH3OH at 294 K. The crystal structure of the product vertical bar K2.35Ag1.1(Ag4Cl4)(0.45)(C3H3O3)(1.1)(K3Cl)(3.45)(K-3(OH)(2))(0.55)(H2O)(>= 3.0)vertical bar-[Si12Al12O48]-LTA (a = 12.292(1) angstrom) was determined by single-crystal X-ray diffraction in the cubic space group Pm (3) over barm at 294 K. It was refined to the final error index, R-1 = 0.052, based on the 371 reflections for which F-o > 4 sigma(F-o). Ag4Cl4 nanoclusters were found in about 45% of the sodalite cavities. Each Ag4Cl4 cluster (interpenetrating tetrahedra; symmetry T-d, Ag-Cl = 3.105(17) angstrom) is held in place by the coordination of each of its four Ag+ ions to three oxygens of the zeolite framework (Ag-O = 2.493(5) angstrom) and by the coordination of each of its four Cl- ions to a K+ ion through a 6-ring (Cl-K = 2.70(3) angstrom). In each of the remaining 55% of the sodalite cavities, two reduced planar 1,3,5-tripyrylium cations, [(CH)(3)O-3](2)(2+) (C-O = 1.52(3) angstrom), are found. These parallel eclipsed rings (symmetry D-3d) have an interplanar distance of only 2.43 angstrom due to sigma double bonding between the rings, the result of four electrons in 12-center bonding pi* orbitals, and to polar attraction. Each ring makes three strong hydrogen bonds (CH center dot center dot center dot O = 2.84(3) angstrom) to oxygens of the zeolite framework, and a Ag+ ion coordinates to the three oxygens of one ring (Ag-O = 2.68(9) angstrom). The large cavities are filled with K+, Cl-, Ag+, OH-, and H2O; the K3Cl2+ unit predominates. The 1,3,5-tripyrylium ring, isoelectronic with benzene, had not been reported before.