A novel photoactive complex was constructed from two non-photoactive ligands and cobalt (II) ions. Upon ultra violet (UV) irradiation (365 nm), the color of complex 1 changes from orange to violet. The ESR spectrum indicates that the photoactive phenomenon of complex 1 originates from an intermolecular energy transfer between the H5DDCPBA ligand and phenanthroline ligand. This photoactive complex shows high thermal stability according to the investigation of thermogravimetric analyses. In addition, the temperature dependence of magnetic susceptibilities for the orange complex 1 was also investigated systematically.
