Synthesis, Spectroscopic Studies, Thermal Stability and Crystal Structure of New Bidentate Schiff Base and Its Cadmium Complex

A new asymmetric bidentate Schiff base ligand was synthesized from a condensation reaction between 2,4-dichlorobenzaldehyde (C7H4Cl2O) and 1,3-pentanediamine (C5H14N2). A cadmium complex was prepared by adding Cd(II) iodide dissolved in methanol to a methanolic solution of the Schiff base ligand, in a ratio of 1:1. The ligand was characterized by elemental, spectroscopic (IR, <sup>1</sup>H NMR), and thermogravimetric analyses. The ligand structure, thermally very stable, is revealed to be bidentate with two potential N-donor sites. The crystal structure of the Schiff base was elucidated by X-ray diffraction analysis. Compound crystallizes in a monoclinic system with a space group P21/n and a number of units per unit cell Z = 4. The unit cell parameters are: a =7.3885(2), b =16.9332 (4), c = 15.5624(4), and β = 90.4306(10). In the asymmetric unit of the ligand, the benzene rings C08/C10/C09/C11/C21/C17 and C20/C15/C13/C18/C22/C24 are in trans position with the aliphatic group with respect to the bonds (C07-N05) and (C19-N06), respectively. In addition, these two aromatic rings are located in two different planes, forming an angle of 3.60º between them, given that the dihedral angle between the ring C08/C10/C09/C11/C21/C17 and the aliphatic group N05-N06 is 67.49º. The spectroscopic data of the complex reveals a mononuclear complex where the Cd(II) ion is housed in a N2I2 coordination site with a slightly distorted tetrahedral geometry. The conductance data indicate that the complex is a neutral electrolyte.