A Unique Layered Cu-formate Hydrate of Cu(HCOO)2?1/3H2O: Structures, Dehydration, and Thermal and Magnetic Properties

作者：Fan Huimin; Wang Bingwu; Wang Zheming^*; Gao Song^*

来源：CHEMICAL RESEARCH IN CHINESE UNIVERSITIES, 2022, 38(1): 107-116.

DOI：10.1007/s40242-022-1457-7

• Copper formate
• Layered structure
• Dehydration
• Thermal expansion
• Magnetism

A new layered Cu-formate hydrate of Cu(HCOO)(2)center dot 1/3H(2)O is unique in its water content and the strongly waved (4,4) Cu-formate layers held by interlayer weak axial Cu-O-formate bonds and O-HwaterMIDLINE HORIZONTAL ELLIPSISOformate hydrogen bonds. The crystal is in orthorhombic space group Pbcn, with cell parameters at 80 K: a=7.9777(2) A, b=7.3656(2) A, c=21.0317(5) A(1 A=10(-1) nm), and V=1235.83(5) A(3). The Cu2+ ions are in the environments of a square pyramid and elongated octahedron, in a ratio of 1/2 within the structure. In the layer, Cu2+ ions are connected by anti-anti formates via short basal Cu-O bonds. The structure remains unchanged until the dehydration that produces the layered anhydrous beta-Cu(HCOO)(2), and the possible transformation mechanism, supported by diffraction evidence, is the reorganization of the Cu-O-formate bonds across the parent layers after dehydration. The two phases exhibit anisotropic thermal expansion behaviors closely relevant to the transverse thermal vibrations of the constituents. Cu(HCOO)(2)center dot 1/3H(2)O is a 2-dimensional Heisenberg antiferromagnet, and exhibits a global spin-canted antiferromagnetism with the Neel temperature of 32.1 K. This is not only higher than that of the magnetically denser beta-Cu(HCOO)(2), but also the highest among the copper formate frameworks.

• 单位
  北京大学