Synthesis, structure and magnetic properties of the hydrothermal reaction product of cobalt (II) ion and the mono-carboxylic acid, transcinnamic acid, (cina) are described. The 2-D coordination polymer, [Co(cina)(2)(H2O)(2)](n), consists of square-grid layers with O-C-O bridging the cobalt atoms sandwich by -CHCHC6H5 in the galleries. The temperature dependence of the magnetic moment revealed a lowering at low temperatures due to the presence of spin orbit coupling.