On verdigris, part I: synthesis, crystal structure solution and characterisation of the 1-2-0 phase (Cu3(CH3COO)2(OH)4).
On verdigris, part I: synthesis, crystal structure solution and characterisation of the 1-2-0 phase (Cu3(CH3COO)2(OH)4).
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DOI：
10.1039/c7dt03288a
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发表时间：
2017-11
影响因子：
4
通讯作者：
S. Bette;R. Kremer;G. Eggert;C. Tang;R. Dinnebier
中科院分区：
文献类型：
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作者：
S. Bette;R. Kremer;G. Eggert;C. Tang;R. Dinnebier
对已知的碱性醋酸铜(II)的合成方法进行了重新研究，发现部分合成方法是不可复制的。通过改变反应条件，成功地合成了1-2-0相(Cu3(CH3COO)2(OH)4=1CuCH3COO)2·2Cu2·0H2O。通过元素分析和热分析确定了产物的物相组成，并用同步辐射X射线粉末衍射仪(XRPD)确定了产物的晶体结构。1-2-0相属于Pbca空间群，晶胞参数为a=20.9742(1)？，b=7.2076(1)？，c=13.1220(1)？晶体结构由Cu2(CH3-COO)2(OH)4/3(OH)2/21/3-二聚体组成，这些二聚体通过角点共享的Cu2(OH)2/3(OH)2/21/3+正方形相互连接，形成垂直于a轴的层状结构。固体的深蓝色源于472 nm的最大反射率和676 nm的最大吸光度，可与其他历史悠久的蓝色颜料如天青石或埃及蓝相媲美。还研究了固体的红外光谱和拉曼光谱性质，结果表明，所得产物与先前通过应用历史程序合成的眩晕相完全相同。因此，我们对标题化合物的参考数据将有助于更好地理解历史上的韦迪格里斯样品中出现的多相混合物。研究了1-2-0相的磁性。在低温下，磁化率可以用自旋-1/2海森堡链很好地描述，该链只有三个铜磁矩中的一个具有均匀的反铁磁性近邻自旋交换耦合。由于Cu2(CH3-COO)2(OH)4/3(OH)2/21/3-二聚体具有很强的反铁磁耦合作用，在∼140K以上，它们对磁性的贡献变得相关，这导致存在两个不同的温度区域，在那里发现了不同居里常数和魏斯温度的磁化率的居里-魏斯行为。
Known synthesis approaches for basic copper(ii) acetates, the main components of historic verdrigis pigments were reinvestigated and revealed to be partially irreproducible. A modification of the reaction conditions led to the successful and reproducible synthesis of the 1-2-0 phase (Cu3(CH3COO)2(OH)4 = 1Cu(CH3COO)2·2Cu(OH)2·0H2O). The phase composition was derived from elemental and thermal analysis and confirmed by the crystal structure solution using synchrotron X-ray powder diffraction (XRPD) data. The 1-2-0 phase crystallises in space group Pbca with lattice parameters of a = 20.9742(1) Å, b = 7.2076(1) Å, and c = 13.1220(1) Å. The crystal structure consists of Cu2(CH3-COO)2(OH)4/3(OH)2/21/3- dimers, which are interconnected by corner sharing Cu(OH)2/3(OH)2/21/3+ squares forming layers perpendicular to the a-axis. The deep blue color of the solid originates from a reflectance maximum at 472 nm and from an absorbance maximum at 676 nm that is comparable with other historic blue pigments like azurite or Egyptian blue. IR- and Raman-spectroscopic properties of the solid were investigated as well, which demonstrated that the obtained product is identical with a previously synthesised verdigris phase that was obtained by applying historical procedures. Therefore, our reference data for the title compound will help to improve the understanding of the multiphase mixtures occurring in historic verdigris samples. The magnetic properties of the 1-2-0 phase were also investigated. At low temperatures the magnetic susceptibility is well described by a spin-1/2 Heisenberg chain with uniform antiferromagnetic nearest-neighbour spin exchange coupling of only one of three Cu magnetic moments. Due to the very strong antiferromagnetic coupling of the Cu2(CH3-COO)2(OH)4/3(OH)2/21/3- dimers their contribution to magnetism becomes relevant above ∼140 K, which results in the presence of two distinct temperature regions where Curie-Weiss behaviour of the magnetic susceptibility with different Curie constants and Weiss temperatures is found.