Maspoch Daniel, Domingo Neus, Ruiz-Molina Daniel, Wurst Klaus, Hernandez Joan Manel, Lloret Francesc, Tejada Javier, Rovira Concepció, Veciana Jaume
Institut de Ciència de Materials de Barcelona, CSIC, Campus Universitari de Bellaterra, 08193 Cerdanyola, Spain.
Inorg Chem. 2007 Mar 5;46(5):1627-33. doi: 10.1021/ic061815x. Epub 2007 Feb 8.
We report the synthesis, crystal structures, and magnetic properties of a series of mononuclear, metal-radical complexes with first-row transition-metal ions using a new class of radical-based ligands, the polychlorinated triphenylmethyl (PTM) radicals. Crystal structures of three new PTM-based complexes of general formula M(PTMMC)2(py)4-x(H2O)x [PTMMC = PTM radical functionalized at the para position with one carboxylic group; M = Zn(II), x = 2 (1); M = Ni(II), x = 1 (2); M = Co(II), x = 1 (3)] show similar molecular structures in which mononuclear complexes are formed by an octahedral metal ion coordinated by two monodentated PTMMC units. From a magnetic point of view, these similar configurations describe a quasilinear, trimeric magnetic model (PTMMC-M(II)-PTMMC), in which the metal [Ni(II) or Co(II)]-radical magnetic-exchange coupling constants have been determined for the first time. In all of these complexes, the temperature dependence of the magnetic susceptibility reveals moderate antiferromagnetic-exchange coupling constants between the PTMMC radicals and Ni(II) (2J/kB = -47.1 K) and Co(II) ions (2J/kB = -15.2 K) based on the exchange Hamiltonian H = -2JSM(Srad1 + Srad2).
我们报道了一系列使用新型基于自由基的配体——多氯代三苯甲基（PTM）自由基，与第一行过渡金属离子形成的单核金属-自由基配合物的合成、晶体结构和磁性。通式为M(PTMMC)2(py)4-x(H2O)x [PTMMC = 在对位用一个羧基官能化的PTM自由基；M = Zn(II)，x = 2 (1)；M = Ni(II)，x = 1 (2)；M = Co(II)，x = 1 (3)]的三种新型基于PTM的配合物的晶体结构显示出相似的分子结构，其中单核配合物由一个八面体金属离子与两个单齿PTMMC单元配位形成。从磁性角度来看，这些相似的构型描述了一个准线性三聚体磁性模型（PTMMC-M(II)-PTMMC），其中首次确定了金属[Ni(II)或Co(II)]-自由基的磁交换耦合常数。在所有这些配合物中，基于交换哈密顿量H = -2JSM(Srad1 + Srad2)，磁化率的温度依赖性揭示了PTMMC自由基与Ni(II)（2J/kB = -47.1 K）和Co(II)离子（2J/kB = -15.2 K）之间适度的反铁磁交换耦合常数。
