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

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 P2(1)/c, the constitution is [HN(CH(2)CH(2))(3)N](+).[(HO)(2)C(6)H(3)COO](-).H(2)O: the anions and the water molecules are linked by six O-H.O hydrogen bonds to form two-dimensional sheets and each cation is linked to a single sheet by one O-H.N and one N-H.O 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 [H(2)N(CH(2)CH(2))(2)NH(2)](2+).2[(HO)(2)C(6)H(3)COO](-).4H(2)O and [H(3)NCH(2)CH(2)NH(3)](2+).2[(HO)(2)C(6)H(3)COO](-).2H(2)O, 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-H.O 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-H.O 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-H.O and three N-H.O hydrogen bonds.