Acta Crystallographica Section B

Structural Science

Volume 57, Part 3 (June 2001)

research papers

Acta Cryst. (2001). B57, 329-338 [ doi:10.1107/S0108768100019832 ]

Hydrated salts of 3,5-dihydroxybenzoic acid with organic diamines: hydrogen-bonded supramolecular structures in two and three dimensions

C. J. Burchell, G. Ferguson, A. J. Lough, R. M. Gregson and C. Glidewell

Abstract: The trigonally trisubstituted acid 3,5-dihydroxybenzoic acid forms hydrated salt-type adducts with organic diamines. In 1,4-diazabicyclo[2.2.2]octane-3,5-dihydroxybenzoic acid-water (1/1/1) (1), where Z' = 2 in P2₁/c, the constitution is [HN(CH₂CH₂)₃N]⁺·[(HO)₂C₆H₃COO]^-·H₂O: the anions and the water molecules are linked by six O-HO hydrogen bonds to form two-dimensional sheets and each cation is linked to a single sheet by one O-HN and one N-HO hydrogen bond. Piperazine-3,5-dihydroxybenzoic acid-water (1/2/4) (2) and 1,2-diaminoethane-3,5-dihydroxybenzoic acid-water (1/2/2) (3) are also both salts with constitutions [H₂N(CH₂CH₂)₂NH₂]²⁺·2[(HO)₂C₆H₃COO]^-·4H₂O and [H₃NCH₂CH₂NH₃]²⁺·2[(HO)₂C₆H₃COO]^-·2H₂O, respectively. Both (2) and (3) have supramolecular structures which are three-dimensional: in (2) the anions and the water molecules are linked by six O-HO hydrogen bonds to form a three-dimensional framework enclosing large centrosymmetric voids, which contain the cations that are linked to the framework by two N-HO hydrogen bonds; in (3) the construction of the three-dimensional framework requires the participation of cations, anions and water molecules, which are linked together by four O-HO and three N-HO hydrogen bonds.

Keywords: hydrated salts; hydrogen bonds; supramolecular structures; organic diamines.