Amine-intercalated layered Sn^II phosphates with open-framework structures

Abstract

Three new Sn^II phosphate materials, [NH₃(CH₂)₃ NH₂(CH₂)₂NH₂(CH₂)₃ NH₃]·2[Sn₂P₂O₈] (I), [(N₂C₅H₁₄)₂][Sn₄P₄ O₁₆]·3H₂O (II) and [(N₂C₅H₁₄)] [Sn₂P₂O₈]·H₂O (III), have been synthesised by means of hydrothermal methods using N,N'-bis(3-aminopropyl)ethylenediamine (BAPEN; for I) and homopiperazine (H-PIP; for II and III), respectively, as the structure-directing organic amines. The solids I-III have layered architectures. The structures of all three compounds consist of strictly alternating vertex-sharing trigonal-pyramidal SnO₃ and tetrahedral PO₄ moieties forming infinite layers possessing apertures bound by 4- and 8-T atoms (T = Sn, P). The distorted 4- and 8-membered apertures within the layers suggest the subtle influence of the lone-pair of electrons of Sn^II on the structure. The interlamellar space is occupied by the protonated organic amine molecules which interact with the framework through N-H···O hydrogen bonding. The compounds I-III bear some structural relationship to the layered zinc phosphite phases.