Layering in cinnamate structures: The role of cations and anion substituents

Four materials have been used to investigate the effect of the cation and ring substituent on crystal packing. In potassium 3-bromo-trans-cinnamate (1), potassium 3-chloro-trans-cinnamate (2) and sodium 3-chloro-trans-cinnamate (3), the cations are accommodated in continuous two-dimensional layers formed by the interaction between cations and anions. The CC double bonds in 1 and 2 are parallel with optimal geometry for photochemical reaction, whereas 3 is disordered. The identity of the halogen substituent influences the structure through halogen-halogen contacts. In the structure of calcium di-trans-cinnamate (4), calcium-anion coordination leads to the formation of ribbons rather than two-dimensional layers.