On verdigris, part II: synthesis of the 2-1-5 phase, Cu3(CH3COO)4(OH)2·5H2O, by long-term crystallisation from aqueous solution at room temperature.
On verdigris, part II: synthesis of the 2-1-5 phase, Cu3(CH3COO)4(OH)2·5H2O, by long-term crystallisation from aqueous solution at room temperature.
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DOI：
10.1039/c8dt01758a
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发表时间：
2018-06
影响因子：
4
通讯作者：
S. Bette;R. Kremer;G. Eggert;R. Dinnebier
中科院分区：
文献类型：
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作者：
S. Bette;R. Kremer;G. Eggert;R. Dinnebier
在25°C下加入氨水后，铜(II)-醋酸酯水溶液的长期结晶导致在铜绿颜料体系中形成迄今特征不佳的相：Cu(CH3COO)2-Cu(OH)2-H2O。用实验室X射线粉末衍射法(XRPD)成功地解决了晶体结构问题。结构溶液的相组成为Cu3(CH3COO)4(OH)2·5H2O≡2-1-5相，热分析也证实了这一点。2-1-5相属于P21/c(14)空间群，晶胞参数为a=12.4835(2)？，b=14.4246(2)？，c=102.871(1)？和β=10.7333(1)？晶体结构由Cu2(CH3COO)2(CH3COO)1/2(OH)4/3H2O1/6+二聚体通过Cu2(CH3COO)(CH3COO)1/2(OH)2/31/6-方块相连，形成沿c方向排列的链状结构。非配位的水合物水分子插入链间，起到链间相互作用的调节作用。红外光谱和拉曼光谱技术也被用来确认所确定的晶体结构的某些方面。2-1-5相的磁性分解为两个独立的子系统：强反铁磁自旋交换耦合的磁性铜二聚体和弱耦合的铜单体。样品的淡蓝色源于488 nm处的最大反射率，并且与已知的眩晕相显著不同。对几个历史悠久的铜绿兰颜料样品的研究表明，这一阶段作为次要成分和主要成分都存在。因此，我们对标题化合物的参考数据将有助于更好地理解在历史上的verdigris样品中出现的多相混合物。
Long-term crystallisation from aqueous copper(ii)-acetate solution after the addition of ammonia at 25 °C led to the formation of a hitherto poorly characterised phase in the verdigris pigment system Cu(CH3COO)2-Cu(OH)2-H2O. Laboratory X-ray powder diffraction (XRPD) was successfully employed to solve the crystal structure. The structure solution reveals a phase composition of the Cu3(CH3COO)4(OH)2·5H2O ≡ 2-1-5 phase, which was also confirmed by thermal analysis. The 2-1-5 phase crystallises in space group P21/c (14) with lattice parameters of a = 12.4835(2) Å, b = 14.4246(2) Å, c = 10.7333(1) Å and β = 102.871(1)°. The crystal structure consists of Cu2(CH3COO)2(CH3COO)1/2(OH)4/3H2O1/6+ dimers that are interconnected by Cu(CH3COO)(CH3COO)1/2(OH)2/31/6- squares forming chains running in the c-direction. Non-coordinating hydrate water molecules are intercalated inbetween the chains and mediate the inter-chain interaction. IR and Raman spectroscopy techniques were also employed to confirm selected aspects of the determined crystal structure. The magnetic properties of the 2-1-5 phase decompose into two independent subsystems: a strongly antiferromagnetically spin exchange coupled magnetic Cu-Cu dimer and a significantly weaker coupled Cu monomer. The light blue colour of the sample originates from a reflectance maximum at 488 nm and significantly differs from the known verdigris phases. An investigation of several historic verdigris pigment samples revealed that this phase occurs both as a minor and a major component. Hence, our reference data for the title compound will help to improve the understanding of the multiphase mixtures occurring in historic verdigris samples.