Acta Crystallographica Section B

Structural Science

Volume 57, Part 1 (February 2001)

research papers

Acta Cryst. (2001). B57, 95-102 [ doi:10.1107/S0108768100014841 ]

Ethane-1,2-diphosphonic acid as a building block in supramolecular chemistry; a pillared-layer framework and framework-encapsulated cations

P. S. Wheatley, A. J. Lough, G. Ferguson, C. J. Burchell and C. Glidewell

Abstract: The 1:1 adduct of piperazine and ethane-1,2-diphosphonic acid is a salt [C₄H₁₂N₂]²⁺·[C₂H₆O₆P₂]^2-, in which both ions lie across centres of inversion in space group P2₁/c. The anions are linked by a single type of O-HO hydrogen bond [OO, 2.562 (3) Å; HO, 1.73 Å, O-HO, 169°] into (6, 3) nets built from a single type of ring. The cations lie between these nets, linked to them by two types of N-HO hydrogen bond [NO, 2.635 (3) and 2.735 (3) Å; HO 1.72 and 1.82 Å, N-HO, 175 and 177°] such that the cations link adjacent sheets, thus forming a pillared-layer framework. The aquated adduct formed between trimethylenedipiperidine and ethane-1,2-diphosphonic acid is also a salt [C₁₃H₂₈N₂]²⁺·[C₂H₆O₆P₂]^2-·2.8[H₂O], in which there are 12 different types of hydrogen bond, eight O-HO and four N-HO. The anions are linked into chains by pairs of O-HO hydrogen bonds and these chains are linked by the water molecules into a continuous three-dimensional framework. Within the anion/water framework are large voids which contain pairs of cations, linked to the framework by N-HO hydrogen bonds.

Keywords: supramolecular chemistry; pillared-layer framework; adducts; hydrogen bonding.