New crystalline modification of terephthalic acid

A series of M(II) (M=Cu, Zn, Cd, Pb) complexes with the physiologically active 2-acetylindan-1,3-dione were synthesized. All complexes were obtained with the metal to ligand ratio 1:2. The presence of two water molecules in the inner coordination sphere of the Zn(II) and Cd(II) complexes was proven. The structure and coordination mode of the newly synthesized Cd(II) and Pb(II) complexes were investigated using NMR (13C CPMAS and 13C NMR in DMF-d7 solution) method. Semiempirical (PM3) and ab initio (ECP-31G) calculations of the structure and IR spectra of the free ligand and corresponding metal(II) complexes were performed. It is shown that the structure of the Pb(II) complex differs significantly from the distorted tetrahedral structure of the Cu(II), Zn(II) and Cd(II) complexes.