Self-organized metallo-helicates and -ladder with 2,2′-biphenyldicarboxylate (C14H8O4)2-:: Synthesis, crystal structures, and magnetic properties

We report on the hydrothermal synthesis, single-crystal structures and magnetic properties of three one-dimensional coordination polymers employing the 2,2'-biphenyldicarboxylate dianion, (C14HSO4)(2-), as the bridging component. [M-II(H2O)(4)(C14H8O4)] where M = Co (1) and Ni (2), consist of helical chains of square-planar M-II(H2O)(4) bridged by C14H8O4 with each carboxylate group acting as a mono-dentate ligand. The magnetic properties are those of paramagnets (1: C = 3.34(1) cm(3) K/mol, mu(eff) = 5.17 muB, theta = -51 (1) K; 2: C = 0.985(9) cm(3) K/mol, mu(eff) = 2.81 muB, theta = +27(2) K) with an antiferromagnetic exchange for 1 and a ferromagnetic exchange for 2. Cu-2(C14H8O4)(H2O)(2) (3) is composed of tetracarboxylato-dimeric units bridged into ladders by biphenyl units. The ladders are packed parallel to each other, and narrow channels are present due to insufficient space filling of the biphenyl rings. Its magnetic behavior follows that of a Bleaney-Bowers singlet-triplet model with a gap of 470(10) K.