The Synthesis, Structures And Fluorescent Properties Of Complexes Containing Indole-3-Acetic Acid Ligand

In recent years, as an important natural plant growth regulator, indole carboxylic acid has involved in many physiological and biochemical processes of plant regulation and control, which has a very wide range of physiological functions. Moreover, its preparation is simple, and harmless to living organisms. Therefore, the researchers have paid more and more attention to this kind of compound.In this article, choosing the indole-3-acetic acid (IAH) as the main ligand, five new crystals [Zn(IA)2phen](1), [Zn(IA)24,4'-bipy]n(2), [Cu(IA)4(DMSO)2](3) and [CdI (IA)phen]2(4), [Pb(IA)2]n(CH3OH)(5) were synthesized and characterized by element analyses and IR spectra. In addition, the five crystal structures have been determined by single crystal X-ray diffraction. The crystal structure of 1 has crystallographic two-fold symmetry. Complex 2 is structurally determined to be a one-dimensional zigzag chain polymer of [Zn2(IA)4] bridged by bpy. Complex 3 is a dual-core pyramid structure. In this complex, the oxygen atoms in every carboxyl group chelate with the center ion Cu2+, plus the oxygen atoms in DMSO solvent. Complex 4 displays a dimeric structure in which two Cd(II) ions are bridged through two iodine atoms. Complex 5 with its central ion Pb(II) forms one-dimensional chain polymer bridged by the oxygen atoms in the ligand IA.The investigation of fluorescent properties of complexes 1-5 in aqueous solution shows that all the five complexes have strong fluorescent emission features. And the influences of the different metal cations to the complexes are also investigated. Moreover, complex 1 and 2 show very effective sensing functions to Hg2+ in aqueous solution, indicating that they exhibit highly sensitive and selective behavior for Hg2+ detection, named fluorescence quenching. Meantime, complex 4 show effective sensing function to Pb2+ in solution. The addition of Pb2+ leads to a new absorption peak in the fluorescence spectrum. We also experiment a variety of metal ions response to complex 5. In these ions, Hg2+, Mn2+ shows higher fluorescence intensity than complex 5, while other ions such as Cu2+,Co2+ shows lower fluorescence intensity, Ni2+ ion has the lowest fluorescence intensity, almost quenching. In addition, due to the role of plant growth regulators, we investigate the biological activity of rice seeds on the complex 1, the experiments show that the biological activity of the complex has been largely enhanced. Moreover, the electrochemical and thermal properties of complex 3 are investigated, cyclic Voltammetry result shows that the complex 3 is a reversible process. The initial decompositional temperature of complex 3 is 163.8℃, which of the decomposition range is 163.8℃～550℃, there also accompanied an significant exothermic process in the second stage.Furthermore, the Mulliken atomic charge distributions and the contributive percents of the atoms in the frontier molecular orbits of the complexes 1-4 were calculated on the basis of crystal structure. The results exhibit that the N atom in the ligand has great negative charge, showing potential coordinating function.We also synthesize two organic compound L1, L2, and explore their fluorescent properties, which are influenced by the addition of different metal ions.