Three New Complexes Based on the Flexible Zwitterionic Dicarboxylate Ligand： Synthesis, Structures, and Properties

Three new complexes have been prepared based on the transition metals and zwitterionic dicarboxylate ligand 1,1＇-（1,4-phenylene-bis（methylene））-bis（pyridine-3-carboxylic acid） （L）, whose formulas are {[Cd4（L）（SO4）]· （C1）6}n （1）, [Zn（L）C12], （2）, and [Co（L）C12], （3）, respectively. Complexes 1-3 have been characterized by elemental analyses, IR spectroscopy, XRD, thermal analyses and single crystal X-ray （powder） diffraction. 1 crystallizes in monoclinic space group C2/m, displaying a 2-D layer structure with three unique Cd^2＋ centers. 2 and 3 are iso- morphic structures with the orthorhombic Cmca space group. They exhibit a 1-D zigzag chain, which can be linked to generate a 2-D layer via hydrogen bonding interactions （C--H＇＂O）. Moreover, electrochemical behavior reveals that the redox reaction of 3-CPE is a surface-controlled reaction. And the luminescent properties of the title comlexes have been investigated at room temperature.