Supramolecular magnetic materials of transition metal

Abstract

By using Cu(II) monomeric building block in which 2,2’-bipyrimidine(= bpym) act as a terminal group, two 1-D zigzag chain compounds, $[Cu(bpym)(N_3)_2]n$ (1) and $[Cu(bpym)(dp)(ClO_4)]n(ClO_4)n$ (2) [dp = 4,4’-dipyridyl] were synthesized with the exploit of linear bridging ligand such as azide or 4,4’-dipyridyl. The azide or dp bridges mediated Cu(II) centers too weak to so that very weak magnetic interaction of two complexes were found. The reaction between the dimeric $[Cu_2(bpym)]$ or $[Cu(bpym)]_n$ building block, in which bpym act as a planar bridge, and various dicaroxylate bridging ligands gave five novel Cu(II) complexes: $[Cu_4(bpym)_2(dem)_2(H_2O)_4]n(H_2O)_{2n}(ClO_4)_{4n}$ (dem = diethylmalonate) (1) and $[Cu_5(bpym)_{2.5}(dmm)_{2.5}(SO_4)_{0.5}(H_2O)_4]_n(H_2O)_{6n}(SO_4)_{4n}$ (dmm = dimethylmalonate) (2), $[Cu_2(bpym)_2(H_2O)_2(tp)]_n(H_2O)_{2n}(ClO_4)_{2n}$ (tp = terephthalate) (3), $[Cu_2(bpym)(H_2O)_2(pdc)_2]_n(ClO_4)_{2n}$ (pdc = 3,4-pyridinedicarboxylate) (4) and $[Cu(bpym)(mtm)(H_2O)](H_2O)_4$ (mtm = bis[(methylthio)methylene]malonate) (5). The structure of these complexes varied from monomer to 3-D assemblies according to the coordination type of the dicarboxylate bridging ligand. In 1 and 2 in which the malonate derivatives of one carbon spacing between carboxylates were used, the $[Cu_2(bpym)]$ dimmer were linked by dicarboxylate so that overall 3-D structures were achieved. In 3, the zigzag chain form of $[Cu(bpym)]_n$ building block were sewed by tp bridges so that overall 2-D net structure were found. The complex 4 has the zigzag chain structure in which the dimeric $[Cu_2(bpym)]$ were linked by two pdc bridges. Contrary to the expectation, 5 has monomeric structure. The magnetic studies revealed that all these complexes (1~4) shows the antiferromagnetic interaction which is mainly due to well-known ntiferromagnetic coupler, bpym bridge. Four novel mixed-valence Cu complexes were synthesized by using CN groups: $[Cu^I(CN)_4]_n[...