Inter-String Arrays of Bimetallic Assemblies with Alternative Cu~(2+)-CI-Cu~(2+)and Cu-NC-M(M=Co~(3+),Fe~(3+),Cr~(3+))Bridges:Syntheses,Crystal Structure,and Magnetic Properties

摘要

Three bimetallic assemblies with alternate homometallic bridges through chloride ligands and heterometallic bridges through cyanide ligands of formula[(323)_2Cu_2(CI)M(CN)_6]_n centre dot 2n(H_20),where 323=N,N'-bis(3-aminopropyl)-ethylenediamine and M=Co~(3+) for 1,Fe~(3+) for 2,and Cr~(3+) for 3,were synthesized.They have been characterized structurally,analytically,spectroscopically,and magnetically.All three assemblies crystallize in the monoclinic system in the same space group P2_1,with a=11.642(2)A,b=10.285(3)A,c=13.622(2)A,beta=95.69(3)deg,V=1623.1(6)A~3,and Z=4 for 1;a - 11.681(4)A,b=10.315(3)A,c=13.567(5)A,beta=95.62(3)deg,V=1626.8(9)A~3,Z=4 for 2,and a=11782(4)A,b=10.386(2)A,c=13.755(4)A,beta=95.51(3)deg,V=1657.4(8)A~3,Z=4 for 3.Crystal structure analyses reveal that one-dimensional zigzag chains propagate in two different crystallographic directions(a and b)which are held together during the course of their propagation.All three assemblies have a homometallic Cu-CI-Cu core in common.Assembly 1 exhibits metamagnetic behavior and shows weak antiferromagnetic interactions between Cu~(2+) paramagnetic centers,through the chloride bridges.The Neel temperature,T_N,is 3.5 K,and the critical field is 4 T.In the presence of a magnetic field larger than 4 T,the local spin doublets of Cu~(2+) in the assembly 1 remain in parallel arrangements.Assemblies 2 and 3 may be described as an alternative repetition of the antiferromagnetically coupled Cu-CI-Cu fragment and ferromagnetically coupled Cu-CN-Fe~(3+)/Cr~(3+)fragment.The overall magnetic character of the strings in assemblies 2 and 3 are antiferromagnetic.Ferromagnetic interaction evidenced by the(Cu-CN-Fe~(3+)/Cr~(3+)) fragment was masked by the antiferromagnetic interaction between the Cu~(2+) centers through the chloride bridge.The magnetic properties agree well with those expected for two [323 Cu~(2+)] and a [Fe(CN)]~(3+) unit with spin-orbit coupling effect of the low-spin iron(lll)ions for 2 and for two [323 Cu~(2+)] and a[Cr(CN)]~(3+) unit for 3.In aqueous solution,trinuclear [(323)_2Cu_2M(CN)_6]~+ and dinuclear[(323)CuM(CN)_6]~- species were observed.