Mn and Zn derivatives of 4-ethenyl benzoic acid (eba) were prepared as part of our investigations on the crystal chemistry and solid state reactivity of metal complexes of unsaturated mono and dicarboxylic acids. The complexes were synthetized by reaction in water of the appropriate stoichiometric amounts of the metal mrbonate and eba. After filtration, the clear solutions were allowed to evaporate slowly at room temperature to yield crystalline materials. The compounds, hefore and after exposure to heat or gamma radiation, were characterized by FT-IR and by x-ray diffraction methods. The results are presented in this paper.