Synthesis, structures, luminescence and magnetic properties of two dinuclear μ1,5 dicyanamide bridged copper(II) complexes containing a tetradentate N-donor Schiff base

Two pentacoordinated dinuclear copper(II) compounds of the type [Cu2(bpbd)2(dca)](ClO4/PF6)3 (1/2) [bpbd = N,N′-(bis-(pyridin-2-yl)benzylidene)-1,4-butanediamine; dca = dicyanamide] have been synthesized and characterized on the basis of microanalytical, spectroscopic, thermal and other physicochemical results. Single crystal X-ray diffraction measurements of 1 and 2 have been made to define their coordination spheres as well as intermolecular interactions. Structural analyses reveal that 1 and 2 have two copper(II) centers bound by four N atoms of bpbd and the metal centers are connected by a single μ1,5 dca bridge. Both the copper(II) centers in 1 have distorted trigonal bipyramidal geometry; whereas, in 2 one copper(II) center has a distorted trigonal bipyramidal geometry and the other adopts a distorted square pyramidal environment. In the crystalline state, individual 0D units in 1 and 2 are self-assembled with CH⋯π interactions promoting dimensionalities. Both complexes show intraligand 1(ππ*) fluorescence in DMF solutions at room temperature. Variable-temperature (300-2 K) magnetic susceptibility studies reveal that long μ1,5 dca bridges mediate very weak antiferromagnetic interactions.