Synthesis, crystal structures, and third-order nonlinear optical properties of two novel complexes of H4edbbp with Zn(II), Cd(II)

We synthesized a new organo-diphosphonic acid ligand H2O3PCH(Ph)NH(CH2)2NH(Ph)CHPO3H2 [ethane-1,2-diamino-N,N0-bis(benzyl phosphonic)acid, H4edbbp] and its two complexes [NH3CH(CH3)CH2NH3]2M2(edbbp)2$H2O [MZZn(II) (1), Cd(II) (2)] in this paper. The complexes 1–2 were structurally characterized by means of X-ray single crystal diffraction. The central ion (MZZn or Cd) has a distorted square-pyramidal coordination environment by three oxygen atoms from phosphonate units and two nitrogen atoms of H4edbbp. The fundamental structural units [M2(edbbp)2]4K are linked by extensive intermolecular hydrogen bonds between 1,2-propyldiamine cations and phosphonate oxygen atoms, forming a one-dimensional chain structure. The third-order nonlinear optical (NLO) properties of 2 were determined by Z-scan techniques. NLO refractive index n2, c(3) of 2’s, and hyperpolarizability g values were calculated to be 1.31!10K17 m2 WK1, 3.19!10K11 and 8.57!10K30 esu, respectively. The results indicate that complex 2 exhibits very strong NLO absorption and self-focusing effects. q 2004 Published by Elsevier B.V.