A novel coordination polymer with an unusual [3 × 2] oblique copper(II) grid: [Cu2(HBIMAM)2(C4O4)3(H2O)2]n·2nH2O [BIMAM = bis(imidazol-2-yl)methylaminomethane]. X-ray structure and magnetic characterization

Abstract

This paper reports the synthesis, X-ray structure and magnetic characterization of [Cu2(HBIMAM)2(C4O4)3(H2O)2]n·2nH2O [BIMAM=bis(imidazol-2-yl)methylamino methane]. This compound is made of infinite chains – running along the [110] direction – with copper ions bridged by μ1,3-squarato ligands. Furthermore, these chains are further cross-linked through additional squarate anions (with the same μ1,3-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 2–300K 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 (Jchain=−0.97(1)cm−1 and j′=−0.03(1)cm−1) is compared with that observed in related hexacoordinated copper(II) compounds containing μ1,3-squarato bridges.