A novel coordination polymer with an unusual [3.2] oblique copper(II) grid: [Cu_2(HBIMAM)_2(C4O4)_3(H_2O)_2]n2nH2O [BIMAM = bis(imidazol-2-yl)methylaminomethane]. X-ray structure and magnetic characterization Dedicated to the memory of Juan Server-Carrio deceased on March 19, 2013 and to the memory of Prof. Purificacion Escribano

摘要

This paper reports the synthesis, X-ray structure and magnetic characterization of [Cu_2(HBIMAM)_2(C_4O _4)_3(H_2O)_2]_n· 2nH_2O [BIMAM = bis(imidazol-2-yl)methylamino methane]. This compound is made of infinite chains - running along the [1 1 0] direction - with copper ions bridged by μ_(1,3)-squarato ligands. Furthermore, these chains are further cross-linked through additional squarate anions (with the same μ_(1,3)-bis(monodentate) bridging mode) to generate two-dimensional sheets parallel to the ab plane. There are inter-chains links every two copper atoms in a chain, forming an unusual (3 × 2) oblique copper(II) grid. Magnetic susceptibility measurements in the range 2-300 K show weak antiferromagnetic exchange interactions. A detailed analysis of the structure shows that the more appropriate model to be used to reproduce the magnetic properties is a regular S = 1/2 antiferromagnetic chain model including an inter-chain interaction (j′). Finally, the observed magnetic behavior (J_(chain) = -0.97(1) cm~(-1) and j′ = -0.03(1) cm ~(-1)) is compared with that observed in related hexacoordinated copper(II) compounds containing μ_(1,3)-squarato bridges.