Reactions of Cu(hfacac)(2).H(2)O (hfacac = hexafluoroacetylacetonate) with pyrazine, 3-cyanopyridine, 1,2-bis(4-pyridyl)ethane, and 4,4'-trimethylenebipyridine in methylene chloride have been studied. Two types of products were obtained and crystallographically characterized: compounds 1 (Cu(hfacac)(2)(pyrazine)(2), orthorhombic, Pbca; a = 9.839(2) Å, b = 17.984(2) Å, c = 13.572(2) Å, Z = 4) and 2 (Cu(hfacac)(2)(3-cyanopyridine)(2), triclinic, P&onemacr;, a = 13.175(2) Å, b = 13.955(2) Å, c = 7.936(2) Å, alpha = 104.29(2) degrees, beta = 105.90 degrees, gamma = 81.47(1) degrees, Z = 2) were isolated as molecular complexes, while compounds 3 (Cu(hfacac)(2)(1,2-bis(4-pyridyl)ethane, monoclinic, P2(1)/c, a = 7.922(1) Å, b = 16.266(4) Å, c = 10.163(2) Å, beta =93.83(1) degrees, Z = 2) and 4 (Cu(hfacac)(2)(4,4'-trimethylenebipyridine), monoclinic, Pc, a = 7.940(1) Å, b = 9.691(2) Å, c = 18.539(3) Å, beta = 95.83(2) degrees, Z = 2) were isolated as one-dimensional infinite polymeric chains. The structures were further characterized by infrared spectroscopy, thermogravimetry, and elemental analysis; additionally, the magnetic behavior of all compounds was investigated and found to follow the Curie law. All four compounds feature similar 4 + 2 pseudooctahedral coordination environments around the Cu(II) centers composed of square-planar Cu(hfacac)(2) units with the N-donor ligands occupying the trans positions. The length of the N-donor ligands determines the formation of either molecular complexes (1 and 2, short ligands) or infinite polymeric structures (3 and 4, longer ligands). Important C-F.H-C hydrogen-bonding interactions in compounds 1 and 3 play a significant role in aligning the molecules and the polymer strands in the crystalline solids.