Ferromagnetic copper(II)-copper(II) interaction in a single chlorido and dicyanamido bridged mixed-valence copper(I/II) 2-D polymer generated by in situ partial reduction of copper(II)

摘要

A mixed-valence 2-D Cu(I/II) complex, [{Cu(II)(dmen)(-Cl)((1,5)-dca)}{Cu(I)((1,5)-dca)}](n) (1) (dmen=N,N-dimethylethylenediamine, dca=dicyanamide=[N(CN)(2)](-)), has been synthesized by in situ partial reduction of Cu(II) to Cu(I) using benzoin (2-hydroxy-1,2-di(phenyl)ethanone) as reductant. Complex 1 was characterized by spectroscopic techniques, single crystal X-ray diffraction, and low temperature magnetic measurements. Structural investigation reveals that 1 represents a mixed-valence 2-D coordination polymer formed by parallel 1-D [Cu(II)(dmen)(Cl)Cu(I)((1,5)-dca)(2)](n) chains running along the b axis, where chloride bridges Cu(II) ions of adjacent polymers through long connections (2.8401(1) angstrom) to form a 2-D network. The metal centers have two different geometrical environments (distorted square pyramidal and distorted trigonal planar geometries for Cu(II) and Cu(I), respectively). The Cu(II) ions in [Cu(II)(dmen)(-Cl)(dca)](n) are interconnected through single chloride bridges while within the [Cu(I)((1,5)-dca)](n) units, the dca connects adjacent Cu(I) ions through (1,5)-dca bridges. Magnetic susceptibility measurements reveal weak ferromagnetic interactions (J=+0.3cm(-1)) within the chlorido-bridged Cu(II) regular chain present in 1. Simultaneous presence of (1,5)-dca and single chlorido bridges with ferromagnetic coupling is believed to be unique in mixed-valence Cu(I)/Cu(II) complexes.