Single Crystal Structure of Zeolite A (LTA) Containing Ag₄Cl₄Nanoclusters and Reduced 1,3,5-Tripyrylium Dimers with Remarkably Short 2.43 Å 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 AgNO 3 . It was washed with CH 3 OH and allowed to react with a stream of 0.05 M KCl in CH 3 OH at 294 K. The crystal structure of the product |K 2.35 Ag 1.1 (Ag 4 Cl 4 ) 0.45 (C 3 H 3 O 3 ) 1.1 (K 3 Cl) 3.45 (K 3 (OH) 2 ) 0.55 (H 2 O) g3.0 |-[Si 12 Al 12 O 48 ]-LTA (a ) 12.292(1) Å) was determined by single-crystal X-ray diffraction in the cubic space group Pm3 j m at 294 K. It was refined to the final error index, R 1 ) 0.052, based on the 371 reflections for which F o > 4σ(F o ). Ag 4 Cl 4 nanoclusters were found in about 45% of the sodalite cavities. Each Ag 4 Cl 4 cluster (interpenetrating tetrahedra; symmetry T d , Ag-Cl ) 3.105(17) Å) 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) Å) and by the coordination of each of its four Cl -ions to a K + ion through a 6-ring (Cl-K ) 2.70(3) Å). 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) Å), are found. These parallel eclipsed rings (symmetry D 3d ) have an interplanar distance of only 2.43 Å due to σ double bonding between the rings, the result of four electrons in 12-center bonding π* orbitals, and to polar attraction. Each ring makes three strong hydrogen bonds (CH · · · O ) 2.84(3) Å) to oxygens of the zeolite framework, and a Ag + ion coordinates to the three oxygens of one ring (Ag-O ) 2.68(9) Å). The large cavities are filled with K + , Cl -, Ag + , OH -, and H 2 O; the K 3 Cl 2+ unit predominates. The 1,3,5-tripyrylium ring, isoelectronic with benzene, had not been reported before.

Artificial Photosynthesis

“…A large variety of photoactive materials have been studied in which zeolites host metal cations, metal clusters, metal complexes and also rare earth complexes [64][65][66][67][68][69][70][71][72].…”

Surprising Intrazeolitic Chemistry of Silver

“…Although the positive charge formally resides on the oxygen atoms, calculations show that it is rather evenly distributed among the carbon and hydrogen atoms. 33 Accordingly, the distortion to the ring may be attributed to repulsion among the carbon atoms. Except for the 1.1 Ag + ions per unit cell, reaction 9 is similar to reaction 7 in section 6; it is again an oxidative trimerization.…”

“…Indeed, the intended nanoparticles were found in the crystal already described in section 7. 33 They were seen to be Ag 4 Cl 4 , neutral tetrahedrally distorted cubes, occupying sodalite cavities (Figure 13). These Ag 4 Cl 4 molecules are structural units of the bulk material, AgCl(s), as hexasilver was with regard to Ag(s).…”

“…It was not the tripyrylium ring, but its reduced dimer, (C 3 O 3 H 3 ) 2 2+ , that was found in Ag-A (Figure ). The two rings of the dimer are parallel and eclipsed but are rotated 60° with respect to one another. A Ag + ion is atop one ring, and another may be below the other, both on the 3-fold axis of the dimer (symmetry 3̅ m = D 3 d ).…”

“…The ring angles are O−C−O = 90(6) o and C−O−C = 150(5) o . Although the positive charge formally resides on the oxygen atoms, calculations show that it is rather evenly distributed among the carbon and hydrogen atoms 33. Accordingly, the distortion to the ring may be attributed to repulsion among the carbon atoms.…”