Synthesis, structure determination and characterization of a new layered aluminophosphate templated by piperazinium ions

Abstract

The synthesis and the crystal structure of a new layered aluminophosphate templated with doubly protonated piperazine molecules are reported. The aluminophosphate has the composition (C 4N 2H 12) 4.5[Al 3P 4O 16] 3·5H 2O and crystallizes in space group P2 1/c(no. 14) with a=22.04(3), b=19.11(2), c=16.479(12) A ̊ and β=99.91(7)°. The aluminophosphate sheets contain PO 4 tetrahedra linked to three AlO 4 tetrahedra in a strictly alternating fashion, the fourth bond being a PO bond. These sheets consist of two types of chains (A and B) running along the [0 0 1] direction in the sequence AABAAB. The part of the sheets formed by chains A is identical to that already found in a layered aluminophosphate prepared with 1,2-diaminopropane. Chain B consists of phosphate-capped 6-MR units linked along the [0 0 1] direction. The connection of the different chains along [1 0 0] forms a new 4.6 net with rows of fused six rings. The inorganic sheets are separated by and hydrogen bonded to doubly protonated piperazine molecules which adopt two types of orientation. The compound was characterized by solid-state NMR and the 2D 27 Al NMR spectrum was partially assigned to the different crystallographic sites of the structure.