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

The synthesis and the crystal structure of a new layered aluminophosphate t emplated with doubly protonated piperazine molecules are reported. The alum inophosphate has the composition (C4N2H12)(4.5)[Al3P4O16](3) (.) 5H(2)O and crystallizes in space group P2(1)/c(no. 14) with a = 22.04(3), b = 19.11(2 ), c = 16.479(12) Angstrom and beta = 99.91(7)degrees. The aluminophosphate sheets contain PO4 tetrahedra linked to three AlO4 tetrahedra in a strictl y alternating fashion, the fourth bond being a P=O bond. These sheets consi st 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-diam inopropane. Chain B consists of phosphate-capped 6-MR units linked along th e [0 0 1] direction. The connection of the different chains along [1 0 0] f orms a new 4.6 net with rows of fused six rings. The inorganic sheets are s eparated by and hydrogen bonded to doubly protonated piperazine molecules w hich adopt two types of orientation. The compound was characterized by soli d-state NMR and the 2D(27)Al NMR spectrum was partially assigned to the dif ferent crystallographic sites of the structure. (C) 2001 Elsevier Science B .V. All rights reserved.