Two 3D supramolecular complexes [Cu-2(trans-oxpn)(phth)](n). 2nH(2)O, 1, and [Cu-2(trans-oxpn)(mu-OH)(mu-H2O)](n)- Br-n. 2nH(2)O, 2 [H(2)oxpn = N,N'-bis(3-aminopropyl)oxamide, phth = phthalate], were synthesized and characterized by single-crystal X-ray crystallography, thermal analyses, and magnetic measurements. 1 crystallizes in the monoclinic space group P2(1)/c with a = 8.578(2) Angstrom, b = 15.596(2) Angstrom, c = 15.657(2) Angstrom, beta = 101.29(2)degrees, Z = 4; 2 crystallizes in the trigonal space group R(3) over bar c with a 15.266(2) Angstrom, b = 15.266(2) Angstrom, c = 34.953(5) Angstrom, and Z = 18. The neutral 2D sheetlike coordination polymer [Cu-2 (trans-oxpn)(phth)](n) in 1 contains alternate transoxamidate and phthalate bridges and then is joined together by H2O molecules via the hydrogen bond linkage Cu(oxpn)... H2O ... H2O ...(oxpn)Cu to produce a 3D supramolecular structure. The cationic chains [Cu-2(trans oxpn)(mu-OH)(mu-H2O)](n)(n+) in 2 contain alternate trans-oxamidate, mu-OH, and mu-H2O bridges and are arranged in three directions, intersecting with one another to yield an extended network via the interchain hydrogen bonds formed by metal-coordinated OH- with the linkages Cu(oxpn)-OH ... OH-Cu(oxpn). Magnetic calculations showed the presence of antiferromagnetic exchange interactions for both complexes. The 2D magnetic coupling system of 1 was simplified into interacting dimers Cu(trans-oxpn)Cu, with the coupling via phth as an interdimer interaction and the data were interpreted with a modified Bleaney-Bowers equation leading to J = -456.7 cm(-1) and theta = 22.0 K. 2 was analyzed qualitatively by an alternating chain model taking into account the interchain interaction in a molecular model with J(1) = -309.6 cm(-1), J(2) = -63.5 cm(-1), and theta = -12.9 K, where J(1) and J(2) denote the coupling constants of the bridges oxamidate and mu-OH, respectively.