Morphological influence of functionalized and non-functionalized α,ω-dicarboxylates on calcite crystallization

The influence of a range of α,ω-dicarboxylates on the morphology of calcite crystals grown from supersaturated bicarbonate solutions was studied by optical and scanning electron microscopy. At Ca/malonate ≈ 3, spindle-shaped crystals elongated along the c axis and with curved {110} prismatic faces were formed. This effect was reduced with increasing chain length. The unsaturated derivative, maleate, was intermediate in potency compared with the saturated malonate and succinate compounds. In contrast, the trans isomer, fumarate, had minimal morphological effect. Functionalization of the lower chain acids had a marked influence on crystal morphology. Crystals grown in the presence of aspartate (α-aminosuccinate) exhibited well defined {110} prismatic faces at Ca/additive = 17, whilst γ-carboxyglutamate had a pronounced effect at ratios as high as 85. The stabilization of the {110} faces of calcite by α,ω-dicarboxylate binding is described in terms of electrostatic, geometric and stereochemical recognition at the crystal/additive interface.