| Abstract
| - The complexation of 3-hydroxysalamo (H4L) with zinc(II) acetate gave an octanuclear zinc(II) cluster [L4Zn8(H2O)3], whose tetrameric structure was determined by X-ray crystallography. The octanuclear cluster also exists in solution, maintaining a conformation similar to that in the crystal structure. In addition, the formation process of the octanuclear complex is highly cooperative. Complexation with cobalt(II) acetate resulted in a similar octanuclear cobalt(II) cluster, in which antiferromagnetic coupling was observed.
- We have synthesized an octanuclear zinc(II) cluster [L4Zn8(H2O)3] by the complexation of 3-hydroxysalamo (H4L)with zinc(II) acetate. The complex crystallizes in the triclinic system, space group P1̄, with unit cell parameters a= 18.233(10) Å, b = 20.518(11) Å, c = 21.366(11) Å, α = 98.7557(2)°, β = 99.191(11)°, γ = 108.309(10)°,and Z = 4. The crystallographic analysis revealed the S4 symmetrical assembling of four ligands and that thetetrameric complex has three water molecules in an unsymmetrical fashion. Spectroscopic analysis of the complexstrongly suggests that the octanuclear cluster also exists in solution and maintains a conformation similar to thatin the crystal structure, although exchange of the coordinating water molecules presumably takes place. In addition,the formation process of the octanuclear complex is highly cooperative. A high coordinating ability of the [(salamo)Zn] unit as well as the catecholato2- moieties probably stabilizes the octanuclear assembly and makes thecomplexation process cooperative. The corresponding octanuclear cobalt(II) cluster [L4Co8(EtOH)3] was preparedin a similar manner. Complex [L4Co8(H2O)2X] (X = H2O or EtOH) was obtained by the recrystallization from chloroform/hexane. The complex crystallizes in the triclinic system, space group P1̄, with unit cell parameters a =15.2359(10) Å, b = 16.9625(12) Å, c = 18.9325(13) Å, α = 101.9710(10)°, β = 105.5410(10)°, γ = 97.1290(10)°, and Z = 2. Temperature dependence of magnetic susceptibility showed a continuous decrease in the χMTvalue with decreasing temperature, suggesting antiferromagnetic interaction among cobalt(II) ions. The magneticsusceptibility above 40 K obeys the Curie−Weiss law with a Weiss constant θ of −39 K and a Curie constant Cof 19.7 cm3 K mol-1.
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