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

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 [1 1 0] 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 2–300 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 (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.

The Cu(II) coordination polymer [Cu2(HBIMAM)2(C4O4)3(H2O)2]n·2nH2O [BIMAM = bis(imidazol-2-yl)methylaminomethane] is a rare example of (3 × 2) oblique Cu(II) grid. Its structure is made of μ1,3-squarato-bridged chains which are further cross-linked through additional squarate anions connecting one of every two Cu(II) atoms to generate rectangular layers. Magnetic susceptibility measurements show weak antiferromagnetic exchange interactions through the squarate bridges that can be reproduced with a regular S = 1/2 antiferromagnetic chain model (Jchain = -0.97 cm−1) with very weak inter-chain interactions (j′ = −0.03 cm−1).Figure optionsDownload as PowerPoint slide