2024-11-21 星期四
Unexpected Assembly of a Unique Cyano-Bridged Three-Dimensional Cu3Cr2 Ferromagnet
Hui-Zhong Kou,† Song Gao,*,† Jing Zhang,† Ge-Hui Wen,‡ Gang Su,§ R. K. Zheng,‡ and X. X. Zhang‡
State Key Laboratory of Rare Earth Materials Chemistry and Applications PKU-HKU Joint Laboratory on Rare Earth Materials and Bioinorganic Chemistry College of Chemistry and Molecular Engineering Peking University, Beijing 100871, China Department of Physics The Hong Kong University of Science and Technology Clear Water Bay, Kowloon, Hong Kong, China Department of Physics The Graduate School of the Chinese Academy of Sciences P.O. Box 3908, Beijing 100039, China
ReceiVed July 19, 2001
Much attention is currently being devoted to the design and synthesis of molecular magnetic materials exhibiting spontaneous magnetization. The main synthetic strategy is virtually to use and connect two paramagnetic building blocks (bricks) to generate polynuclear or extended arrays. Extended arrays of high dimensionalities may exhibit higher ordering temperatures due to the increased number of interacting neighbors. A representative example is the cyano-bridged three-dimensional (3D) Prussian blue-type complexes constructed from hexacyanometalate(III) and simple transition metal building blocks.1 One of these materials exhibits long-range magnetic ordering at Tc as high as 372 K.1c Thus far, a number of Prussian blue analogues of different dimensionalities have been synthesized and characterized structurally and magnetically.2,3 These studies have shown that the low-dimensional materials have Tc values generally lower than that of the corresponding 3D analogues, and the few hybrid 3D arrays derived from paramagnetic [M(CN)6]3- and transition metal complexes order at different temperatures depending on the average number of the nearest neighbors around a given metal ion.2b,e,l Since copper(II) ion exhibits great stereochemical plasticity, a large variety of magnetic compounds with hexacyanometalates may be fabricated using Cu(II). Nevertheless, only a few such bimetallic complexes have been reported so far, and most of them were synthesized by the reaction of hexacyanometalate with CuL2+ complexes containing only two available coordination sites, producing low-dimensional species.3 It is worth mentioning that the only complex exhibiting the magnetic phase transition at 11.0 K is [Cu(en)]3[Fe(CN)6]2·3H2O, whose structure is suggested to be 3D.3g To gain an explicit structure−property correlation, we extended this study to a Cu3Cr2analogue. Here we report a unique 3D coordination polymer [Cu(EtOH)2][Cu(en)]2[Cr(CN)6]21with ferromagnetic ordering below 57 K.