Phase diagrams of different substituted acids with 1-heptyl-4-( 4-pyridyl) pyridinium bromide were investigated. The formation of ionic hydrogen-bonded 1:1 and 1:2 associates can be detected in the solid state. In some cases thermodynamically stable smectic A phases are observed. The maximum phase stability in the liquid crystalline state can differ considerably from the expected value for the 1:1 associates. The layer thickness of the smectic layers measured by X-ray methods is smaller than the value calculated from molecular models. This indicates a complicated packing behaviour of the molecular building units in the SmA layers.