The first examples of polymeric complexes that contain the polynitrile dianion hexacyanotrimethylenecyclopropanediide (HCTMCP2 ) were isolated and their magnetic properties have been explored. Complexes of the form (n-TBA)2- [M(HCTMCP)2(H2O)2] (1) (M = MnII, FeII, CoII, CdII) possess (4,4) sheet structures with large cavities that contain the tetra-n-butylammonium (n-TBA) countercations. Synthesis using sodium as the countercation yields a family of products with the general form [M(S)4M(S)2(HCTMCP)2] (S = EtOH, M =FeII (2); S = MeOH, M = CoII or ZnII (3)). These complexes adopt a variety of two-dimensional (2D) structures. The complex [Mn3(HCTMCP)2(H2O)12](HCTMCP) 3 6(H2O) (4) contains cationic (6,3) sheets with the counteranion and solvent molecules encapsulated within the hexagonal windows.Complexes 1 4 display weak antiferromagnetic coupling in all cases. The first example of a complex that contains the CN-coordinated monoanionic radical HCTMCP a?? , [Cu(HCTMCP)(MeCN)2] (5) is described. This one-dimensional (1D) coordination polymer, containing tetrahedral CuI centers, displays medium strength antiferromagnetic coupling that is mediated through I?-interactions between the radical anions on adjacent chains.