Mukherjee Arindam, Raghunathan Rajamani, Saha Manas K, Nethaji Munirathinam, Ramasesha Suryanarayanasastry, Chakravarty Akhil R
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Sir C. V. Raman Avenue, Bangalore 560 012, India.
Chemistry. 2005 May 6;11(10):3087-96. doi: 10.1002/chem.200401048.
Three cubane copper(II) clusters, namely [Cu(4)(HL')4] (1), [Cu4L2(OH)2] (2), and [Cu4L2(OMe)2] (3), of two pentadentate Schiff-base ligands N,N'-(2-hydroxypropane-1,3-diyl)bis(acetylacetoneimine) (H3L') and N,N'-(2-hydroxypropane-1,3-diyl)bis(salicylaldimine) (H3L), are prepared, structurally characterized by X-ray crystallography, and their variable-temperature magnetic properties studied. Complex 1 has a metal-to-ligand stoichiometry of 1:1 and it crystallizes in the cubic space group P43n with a structure that consists of a tetranuclear core with metal centers linked by a mu(3)-alkoxo oxygen atom to form a cubic arrangement of the metal and oxygen atoms. Each ligand displays a tridentate binding mode which means that a total of eight pendant binding sites remain per cubane molecule. Complexes [Cu4L2(OH)2] (2) and [Cu4L2(OMe)2] (3) crystallize in the orthorhombic space group Pccn and have a cubane structure that is formed by the self-assembly of two {Cu2L}+ units. The variable-temperature magnetic susceptibility data in the range 300-18 K show ferromagnetic exchange interactions in the complexes. Along with the ferromagnetic exchange pathway, there is also a weak antiferromagnetic exchange between the copper centers. The theoretical fitting of the magnetic data gives the following parameters: J1 = 38.5 and J2 = -18 cm(-1) for 1 with a triplet (S = 1) ground state and quintet (S = 2) lowest excited state; J1 = 14.7 and J2 = -18.4 cm(-1) for 2 with a triplet ground state and singlet (S = 0) lowest excited state; and J1 = 33.3 and J2 = -15.6 cm(-1) for 3 with a triplet ground state and quintet lowest excited state, where J1 and J2 are two different exchange pathways in the cubane {Cu4O4} core. The crystal structures of 2 * 6 H2O and 3 * 2 H2O * THF show the presence of channels containing the lattice solvent molecules.
制备了三种由两种五齿席夫碱配体N,N'-(2-羟基丙烷-1,3-二基)双(乙酰丙酮亚胺)(H3L')和N,N'-(2-羟基丙烷-1,3-二基)双(水杨醛亚胺)(H3L)形成的立方烷铜(II)簇合物，即[Cu(4)(HL')4] (1)、[Cu4L2(OH)2] (2)和[Cu4L2(OMe)2] (3)，通过X射线晶体学对其进行结构表征，并研究了它们的变温磁性。配合物1的金属与配体化学计量比为1:1，它结晶于立方空间群P43n中，其结构由一个四核核心组成，金属中心通过一个μ(3)-烷氧基氧原子相连，形成金属和氧原子的立方排列。每个配体呈现三齿配位模式，这意味着每个立方烷分子总共还剩下八个悬垂结合位点。配合物[Cu4L2(OH)2] (2)和[Cu4L2(OMe)2] (3)结晶于正交空间群Pccn中，具有由两个{Cu2L}+单元自组装形成的立方烷结构。在300 - 18 K范围内的变温磁化率数据表明这些配合物中存在铁磁交换相互作用。除了铁磁交换途径外，铜中心之间还存在弱的反铁磁交换。磁性数据的理论拟合给出以下参数：对于具有三重态(S = 1)基态和五重态(S = 2)最低激发态的1，J1 = 38.5且J2 = -18 cm(-1)；对于具有三重态基态和单重态(S = 0)最低激发态的2，J1 = 14.7且J2 = -18.4 cm(-1)；对于具有三重态基态和五重态最低激发态的3，J1 = 33.3且J2 = -15.6 cm(-1)，其中J1和J2是立方烷{Cu4O4}核心中的两种不同交换途径。2·6H2O和3·2H2O·THF的晶体结构表明存在包含晶格溶剂分子的通道。
