Competitive forces in crystalline lattices – protonated isonicotinic acid in the presence of tetrachlorometallates

A crystal structure determination for bis(4-hydroxycarbonylpyridinium) chloride tetrachloroferrate(III) monohydrate shows some striking differences in the lattice compared to that of the related tetrachloroplatinate(II) compound. A variety of intermolecular contacts indicate that, while common forces may be operative in these and other related lattices, their diverse features may reflect a close balance between polar hydrogen-bonding interactions and those involving the aromatic rings.