Microwave Synthesis of Highly Functionalized Two-Dimensionally Assemblies of Transition Metal Comprexes

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Recent studies on syntheses, structures, and magnetic properties of ordered polymetallic chains opened a new perspective in the field of low dimensional electronic and magnetic systems. However, very great endeavors to develop the rational synthesis will be necessary before the physical properties of these systems are thoroughly understood. The great difficulties are faced with the preparation of crystalline form, which can provide crystallographic structure. The crystal structures of copper-oxocarbon anion ligand systems have long been seeked by many researchers. However, all the efforts to obtain single crystals have been unsuccessful. We first succeeded in obtaining single crystals of a copper (II) coordination polymer, [Cu_2 (mu-ox) _2 (mu-pz) (pz) _2] _n (1) (ox=oxalate ; pz=pyrazine), by use of microwave oven. 1 crystallizaes in the triclinic, space group P 1 with a=10.578 (4)*, b=11.603 (5)*, c=8.027 (4)*, alpha=92.11 (5)ﾟ, beta=103.10 (3)ﾟ, gamma=76.32 (4)ﾟ, V=932.3 (8)*^3, and Z=2.1 shows an extended sheet structure of copper (II) ions bridged by oxalate anions and pyrazines. The repeating unit of (Cu_2 (mu-ox) _2 (mu-pz) (pz) _2) contains two types of 4+2 coordination environments with O_4N_2, which are characteristic of pz coordination ; one of the two copper atoms has only terminally coordinated pz molecules while the other is linked by bridging pz molecules. The Cu-ox-Cu-sequence displays pleated ribbon, thus planes of CuO_4-ox-CuO_4 forming a boat conformation. In addition to the compound 1, single crystals of [Cu (C_6O_4Cl_2) (pz) ] _n, [Cu (C_6O_4Cl_2) (MeOH) _2] _n, and { [Cu (C_6O_4Cl_2) (H_2O) _2] (H_2O) } _n were obtained. The magnetic susceptibilities were measured down to 2 K and analyzed using the Heisenberg linear chain theory, indicating intersting magnetic behavior. The density functional MO calculation and EHMO band claculations were carried out to delineate the electronic structure.