Charge-assisted N-H(+)•••O(-) and O-H•••O(-) hydrogen bonds control the supramolecular aggregation of ferrocenedicarboxylic acid and bis-amidines

Directional N-H...O and O-H...O hydrogen bonds reinforced by charge assistance in the presence of anion-cation interactions have been used to design and synthesise a whole family of new organic-organometallic supramolecular salts. The compounds [C5H16N4](2+) [(eta(5)-C5H4COO)(2)Fe](2-) . 2C(2)H(5)OH, 1, [C5H16N4](2+) {[(eta(5)- C5H4COOH)(eta(5)-C5H4COO)Fe](2)}(2-), 2,[C7H20N4](2+) [(eta(5)-C5H4COO)(2)Fe](2-) . 4H(2)O, 3,[C7H20N4](2+) {[(eta(5)- C5H4COOH)(eta(5)-C5H4COO)Fe](2)}(2-), 4, and [C7H18O2N4](2+) [(eta(5)-C5H4COO)(2)Fe](2-) . 4H(2)O, 5, have been obtained by reacting [(eta(5)-C5H4COOH)(2)Fe] with the bis-amidines [C5H14N4], [C7H18N4] and [C7H16O2N4]. The self-assembly between singly and doubly deprotonated acids and the protonated cations is controlled by the stoichiometric ratio and by the choice of solvent. The effect of charge assistance on the N-H...O interactions is discussed on the basis of a CSD analysis.