摘要
Anew layered Cu-formate hydrate of Cu(HCOO)2·1/3H2O is unique in its water content and the strongly waved (4,4) Cu-formate layers held by interlayer weak axial Cu-Oformate bonds and O-Hwater···Oformate hydrogen bonds. The crystal is in orthorhombic space group Pbcn, with cell parameters at 80 K:a=7.9777(2) Å, b=7.3656(2) Å, c=21.0317(5) Å(1 Å=10−1 nm), and V=1235.83(5) Å3. 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 β-Cu(HCOO)2, and the possible transformation mechanism, supported by diffraction evidence, is the reorganization of the Cu-Oformate 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)2·1/3H2O is a 2-dimensional Heisenberg antiferromagnet, and exhibits a global spin-canted antiferromagnetism with the Néel temperature of 32.1 K. This is not only higher than that of the magnetically denser β-Cu(HCOO)2, but also the highest among the copper formate frameworks.
基金
This work was supported by the National Natural Science Foundation of China (Nos.21991143,21671008)
the National Basic Research Program of China (No.2018YFA0306003).
