The result of optical X-ray, DSC and magnetic susceptibility studies of new Co(II) metallomesogens are reported. The di-(5-substituted-salicylidene)ethylenediaminato cobalt(II) complexes exhibit broad range Saphases. A comparison with corresponding copper(II) and nickel(II) complexes leads to conclusions about how the properties are influenced by the metal atom. Cobalt(II) complexes of this kind form different modifications which are either active or inactive against oxygen. The conversion process (inactive-active) is monitored by time dependent X-ray diffractometric measurements.