四铜（II）取代杂多阴离子[Cu(4)K(2)(H(2)O)(8)(α-AsW(9)O(33))(2)](8-)的结构与磁性

Structure and magnetism of the tetra-copper(II)-substituted heteropolyanion [Cu(4)K(2)(H(2)O)(8)(alpha-AsW(9)O(33))(2)](8-).

作者信息

Kortz Ulrich, Nellutla Saritha, Stowe Ashley C, Dalal Naresh S, Van Tol Johan, Bassil Bassem S

机构信息

School of Engineering and Science, International University Bremen, PO Box 750 561, 28725 Bremen, Germany.

出版信息

Inorg Chem. 2004 Jan 12;43(1):144-54. doi: 10.1021/ic034697b.

DOI:10.1021/ic034697b

PMID:14704062

Abstract

The novel heteropolyanion Cu(4)K(2)(H(2)O)(8)(alpha-AsW(9)O(33))(2)(-) (1) has been synthesized and characterized by IR spectroscopy, elemental analysis, and magnetic studies. Single-crystal X-ray analysis was carried out on K(7)Na[Cu(4)K(2)(H(2)O)(6)(alpha-AsW(9)O(33))(2)].5.5H(2)O(K(7)Na-1), which crystallizes in the tetragonal system, space group P42(1)m, with a = 16.705(4) A, b = 16.705(4) A, c = 13.956(5) A, and Z = 2. Interaction of the lacunary alpha-AsW(9)O(33)(-) with Cu(2+) ions in neutral, aqueous medium leads to the formation of the dimeric polyoxoanion 1 in high yield. Polyanion 1 consists of two alpha-AsW(9)O(33) units joined by a cyclic arrangement of four Cu(2+) and two K(+) ions, resulting in a structure with C(2)(v)() symmetry. All copper ions have one terminal water molecule, resulting in square-pyramidal coordination geometry. Three of the copper ions are adjacent to each other and connected via two micro(3)-oxo bridges. EPR studies on K(7)Na-1 and also on Na(9)[Cu(3)Na(3)(H(2)O)(9)(alpha-AsW(9)O(33))(2)].26H(2)O (Na(9)-2) over 2-300 K yielded g values that are consistent with a square-pyramidal coordination around the copper(II) ions in 1 and 2. No hyperfine structure was observed due to the presence of strong spin exchange, but fine structure was observed for the excited (S(T) = 3/2) state of Na(9)-2 and the ground state (S(T) = 1) of K(7)Na-1. The zero-field (D) parameters have also been determined for these states, constituting a rare case wherein one observes EPR from both the ground and the excited states. Magnetic susceptibility data show that Na(9)-2 has antiferromagnetically coupled Cu(2+) ions, with J = -1.36 +/- 0.01 cm(-)(1), while K(7)Na-1 has both ferromagnetically and antiferromagnetically coupled Cu(2+) ions (J(1) = 2.78 +/- 0.13 cm(-)(1), J(2) = -1.35 +/- 0.02 cm(-)(1), and J(3) = -2.24 +/- 0.06 cm(-)(1)), and the ground-state total spins are S(T) = 1/2 in Na(9)-2 and S(T) = 1 in K(7)Na-1.

摘要

新型杂多阴离子[Cu₄K₂(H₂O)₈(α - AsW₉O₃₃)₂]⁸⁻（1）已通过红外光谱、元素分析和磁性研究进行了合成与表征。对[K₇Na[Cu₄K₂(H₂O)₆(α - AsW₉O₃₃)₂]·5.5H₂O]ₙ（K₇Na - 1）进行了单晶X射线分析，其结晶于四方晶系，空间群P42(1)m，a = 16.705(4) Å，b = 16.705(4) Å，c = 13.956(5) Å，Z = 2。在中性水介质中，缺位的[α - AsW₉O₃₃]⁹⁻与Cu²⁺离子相互作用，高产率地生成了二聚多氧阴离子1。多阴离子1由两个α - AsW₉O₃₃单元通过四个Cu²⁺和两个K⁺离子的环状排列连接而成，形成具有C₂ᵥ对称性的结构。所有铜离子都有一个端基水分子，形成四方锥配位几何结构。其中三个铜离子彼此相邻，并通过两个μ₃ - 氧桥相连。对K₇Na - 1以及Na₉[Cu₃Na₃(H₂O)₉(α - AsW₉O₃₃)₂]·26H₂O（Na₉ - 2）在2 - 300 K范围内进行的电子顺磁共振（EPR）研究得出的g值与1和2中铜（II）离子周围的四方锥配位一致。由于存在强自旋交换，未观察到超精细结构，但在Na₉ - 2的激发态（Sₜ = 3/2）和K₇Na - 1的基态（Sₜ = 1）中观察到了精细结构。还测定了这些状态的零场（D）参数，这是一种罕见的情况，即同时观察到了基态和激发态的EPR。磁化率数据表明，Na₉ - 2具有反铁磁耦合的Cu²⁺离子，J = -1.36 ± 0.01 cm⁻¹，而K₇Na - 1具有铁磁和反铁磁耦合的Cu²⁺离子（J₁ = 2.78 ± 0.13 cm⁻¹，J₂ = -1.35 ± 0.02 cm⁻¹，J₃ = -2.24 ± 0.06 cm⁻¹），并且基态总自旋在Na₉ - 2中为Sₜ = 1/2，在K₇Na - 1中为Sₜ = 1。