Synthesis And Properties Of Transition Metal Coordination Complexes With Two Different Ligands As Co-ligands

Studies of metal coordination complexes with unique structural features andinteresting magnetic properties have become a fascinating subject in the field ofcoordination chemistry, material chemistry, and condensed matter physics. Althoughmany different bridging groups and transitionmetal ions have been employed for theconstruction of such species, the metal-azido system has received much attentionduring the past decades owing to its various coordination modes and magnetism. Aswell as N3-, the bridging ligands of R-COO-have various coordination modes whichare similar to azido’s. So carboxylate bridged ligands are also applied broadly ingenerating metal coordination complexes. A series of novel complexes based on twodifferent ligands as co-ligand have been gained by hydrothermal method with thestructures and magnetic properties fully investigated. The main points are summarizedas follows:1. A novel copper coordination polymer, [Cu₂（N₃）₃（L¹ï¼‰]n（2-A, HL¹=pyrazine-2-carboxylic acid）, has been synthesized by hydrothermal reaction. Inthe reaction system, Cu^â…¡ions are avoided to reduce to Cu^Iions due to theexistence of Nd^â…¢. It’s found that Cu ions take tetragonal pyramidal andoctahedral coordination geometry, separately. And the complex is a 3D structurebased on two double EO azido bridged trimmers and octahedron Cu^â…¡ions, inwhich the azido ligands take on EO andμ1,1,3mode to form Cu^â…¡-azido 2D layers.Furthermore L1ligands, in which COO-anions take syn-anti mode, pillar 2Dlayers into an infinite 3D framework. And magnetic study indicates thatalternating FM-AF coupling exists in the complex.2. Two novel copper coordination polymer （3-A and 3-B） with benzoate analoguesas co-ligand have been synthesized by hydrothermal reaction. In complex 3-A（C₇H₉CuN₃O₅）, Cu^â…¡ion locates in the invers center within a slightly distortedoctahedral coordination geometry. Two Cuâ…¡ions, linked by oneμ₂water, oneEO azido anion and one p-hydroxybenzoate anion in which carboxylate anionapply syn,syn model, give a 1D chain. Furthermore 1D chains are connected byhydrogen bonds giving a 3D network. In complex 3-B （C⁴2H³8Cu²N²O⁸）, theCu^â…¡ions are coordinated by one 3,5-dimethyl-pyridine ligand and two benzoicacid ligands in a slightly distorted octahedral. And a pair of Cu^â…¡ions areconnected through four independent syn-syn bidentate chelating carboxylatebridges to generate a binuclear unit.3. One novel cobalt-azido coordination polymer （4-A） with 1,10-Phenanthroline （L⁵） as co-ligand has been synthesized by hydrothermal reaction. In complex4-A, the Co（Ⅱ） ion is coordinated by one chelating 1,10-Phenanthroline andfour azido anions forming a distorted CoN₆octahedral environment. The azidoanions take two different coordinated types, in which one bridges two Co（Ⅱ）ions inμ¹,1mode while the other one bridges two Co（Ⅱ） ions inμ¹,3mode. Twoμ¹,1azido anions link two Co（Ⅱ） ions forming a dimer then the dimers linked bythe doubleμ¹,3azido anions give a 1D chain. Pi-pi stacking of thephenanthroline between neighbor chains assists the foming of 3D supermoleculestructure.