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

Abstract

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⁺[(η⁵-C₅H₄COO)₂Fe]²⁻·2C₂H₅OH, 1, [C₅H₁₆N₄]²⁺{[(η⁵-C₅H₄COOH)(η⁵-C₅H₄COO)Fe]₂}²⁻, 2, [C₇H₂₀N₄]²⁺[(η⁵-C₅H₄COO)₂Fe]²⁻·4H₂O, 3, [C₇H₂₀N₄]²⁺{[(η⁵-C₅H₄COOH)(η⁵-C₅H₄COO)Fe]₂}²⁻, 4, and [C₇H₁₈O₂N₄]²⁺[(η⁵-C₅H₄COO)₂Fe]²⁻ ·4H₂O, 5, have been obtained by reacting [(η⁵-C₅H₄COOH)₂Fe] 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.