AbstractTwo new polymeric complexes of copper(II), [Cu(L1)(μ‐fum)(μ‐H2O)]n (1) (fum = fumarate dianion; L1 = N,N′‐dimethylethane‐1,2‐diamine) and [Cu(L2)(μ‐tp)]n (2) [tp = terephthalate dianion; L2 = N‐(2‐aminoethyl)‐3‐amino‐1‐propanol], have been synthesized. The molecular structures are determined by X‐ray crystallography. Complex 1 is a fumarato‐bridged zig‐zag 1D chain of CuII−L1, which is extended to a 3D coordination polymer through bridging water molecules. Complex 2 is a chain of CuII in which the terephthalate anions bridge in alternate bis(bidentate) and bis(monodentate) fashions. The coexistence of such types of bridging modes of terephthalate ions in a single molecule is unprecedented. The chelating terephthalate ion is linked to an equatorial and an axial site of consecutive metal ions, while the other terephthalate ion is axially linked to CuII centers. Both the complexes are characterized by variable‐temperature susceptibility measurements at room temperature down to 4 K. Fitting of the magnetic data reveals the existence of weak antiferromagnetic interactions through the bridging dicarboxylate pathways. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)