Reactions between dinuclear Cu-II-Ni-II complexes and the nitrito ligand: A new one-dimensional complex [Cu(oxpn)Ni(mu-NO2)(trimen)](n)(ClO4)(n) withnitrite acting as a tridentate bridging ligand and ferro- and antiferromagnetic alternation

The reaction of NiX2.6 H2O (X = NO3-, ClO4-), bidentate amine, [Cu(oxpn)] [ oxpn= N,N'-bis(3-aminopropyl)oxamide] and sodium nitrite in ethanolic solut ion, leads to the formation of new Cu2+-Ni2+ complexes of general formula [ Cu(oxpn)Ni(No-2)(aa)](n)(X)(n) [1, X=ClO4-, aa = N,N,N'-trimethylethylenedi amine (trimen); 2, X = ClO4-, aa = N,N,N'N'-tetramethylethylenediamine (tme n); 3, X = ClO4-, aa = N,N-dimethyl-N'-ethylethylenediamine (dmeten); 4, X = PF6-, aa = trimen; 5, X = PF6-, aa = dmeten]. The structure of complex 1 consists of [Cu(oxpn)Ni(trimen)](2+) units linked by a nitrite group acting as a tridentate ligand, giving a one-dimensional system separated by ClO4- anions. In contrast, the structure of complex 2 consists of isolated [Cu(o xpn)Ni(NO2)(tmen)](+) dinuclear units and uncoordinated ClO4- anions. The n itrite group acts as a bidentate ligand. Variable-temperature magnetic susc eptibility studies were performed on 1-5. The J value through the oxamidato bridge is close to -110 cm(-1) in all five cases. For complex 1, considere d as a chain, a simulation of the chi(M)T vs T was performed with the CLUMA G program. These calculations revealed the influence of the magnetic intera ctions between the dinuclear entities through the nitrito bridging ligand, on the susceptibility curves at low temperatures.