Copper benzenedicarboxylate coordination polymers incorporating a long-spanning neutral co-ligand: Effect of anion inclusion and carboxylate pendant-arm length on topology and magnetism

Abstract

Three divalent copper coordination polymers containing aromatic dicarboxylate ligands and the long-spanning tethering imine bis(4-pyridylmethyl)piperazine (bpmp) have been prepared and structurally characterized. The length of the dicarboxylate pendant arms, carboxylate binding mode, and the inclusion of anionic components play a synergistic role in structure direction in this system. {[Cu(ip)(bpmp)(H 2O)]·5H 2O} n (ip = isophthalate, 1) displays neutral (4,4) rectangular coordination polymer grids that stack in an ABCD repeat pattern. Use of the longer pendant arm dicarboxylate 1,3-phenylenediacetate (phda) resulted in {[Cu 2(phda) 2(bpmp)]·H 2O} n ( 2), a 3-D network coordination polymer with primitive cubic topology that features strongly antiferromagnetically coupled ( J = −331(1) cm −1) {Cu 2(CO 2) 4} paddlewheel units. In the presence of excess nitrate ions, {[Cu(phda)(Hbpmp)](NO 3)·3H 2O} n ( 3) was isolated instead of 2; 3 manifests cationic 2-D coordination polymer layers built from weakly antiferromagnetically coupled ( J = −2.43(1) cm −1) {Cu 2O 2} dimers linked through phda and protonated bpmp ligands. The striking difference in magnetic properties is ascribed to the equatorial–equatorial versus axial–equatorial bridging of copper coordination spheres in 2 and 3, respectively.