Hydrothermal Synthesis and Characterization of Two Cobalt Phosphates Based on Double-Four-Ring Units with Fluorine-Occlusion and Phosphite-Substitution Modifications

Abstract

Two new fluorinated microporous cobalt phosphates, (H2en)0.5[F(0.25)Co(H(0.5)PO4)0.5(PO4)0.5].0.25H2O (1) and (H2en)0.5[Fx(H2O)0.25(-x)Co(HPO3)x(PO4)1-x].0.25H2O (x = 0.17; 2), have been synthesized from different P sources, H3PO4 and H3PO3, in the presence of ethylenediamine and F ions. Both structures of 1 and 2 are based on the similar secondary building unit of a double four ring (D4R). 1 crystallizes in the orthorhombic space group Cmcm with a = 14.895(1) A, b = 9.7133(9) A, c = 13.688(1) A, V = 1980.4(3) A(3), and Z = 16 and is built up from fully F-occluded double-four-ring units via corner-sharing Co and P polyhedra and edge-sharing Co polyhedra. 2 crystallizes in the tetragonal space group /42m with a = 10.2033(4) A, c = 9.5545(9) A, V = 994.7(1) A(3), and Z = 8 and adopts an ACO-type framework with strict alternation of corner-sharing Co and P polyhedra. On the basis of the evidence from ion chromatography studies and elemental analyses, 2 contains both phosphate and phosphite ions, and the amount of F ions in 2 is the same as the amount of phosphite ions. This implies that some PO4(3-) groups in 2 are substituted by HPO3(2-) groups with the same amount of F(-) occlusion in the center of D4R as charge compensation. Magnetic susceptibility measurements of both 1 and 2 appear that they contain mainly antiferromagnetic interaction (theta = -27.8 K for 1 and -35.0 K for 2). However, the magnetic coupling is much more complicated in compound 1 because of the Co-O-Co linkages in it. Low-field temperature-dependent magnetization curves of 1 showed spontaneous magnetization in the form of two continuous bumps, one sharp and one broad. This may be related to the temperature dependence of two related but different types of spin canting. At 2 K, 1 also showed a large coercive field of about 5000 Oe.

Framework-structured weak ferromagnets

“…25,[168][169][170][171] Interest is increased by the incorporation of paramagnetic transition-metal ions into the O-P-O bridge based compounds (including phosphate, phosphite phosphonate, phosphinate and pyrophosphate). Since then, interesting magnetic properties such as SCM, 172,173 ferromagnetism, 174-176 metamagnetism [177][178][179] and weak ferromagnetism 172,173,[180][181][182][183][184][185][186][187][188][189][190][191][192][193][194][195] have been observed in some compounds.…”

“…20b), which may be related to the temperature dependence of two related but different types of spin canting. 191 The 3D cobalt compound [Co 2 (P 2 O 7 )(bpym) 2 ]Á12H 2 O (bpym = 2,2 0bipyrimidine) is the first pyrophosphate coordination complex to show a spin-canted AF behavior with T N ca. 19 K and a canting angle of about 1.81.…”

Synthesis and structural characterization of two cobalt phosphites: 1-D (H3NC6H4NH3)Co(HPO3)2 and 2-D (NH4)2Co2(HPo3)3

“…However, cobalt has high coordination flexibility and a strong tendency to form edge-sharing or face-sharing linkages of metal-oxygen polyhedra. These properties usually lead to difficulty in mimicking a zeolitetype structure, but can lead to the possibility of new structural morphology and interesting magnetic properties [3][4][5][6][7][8]. Recently, the HPO 3 group has been investigated as a possible replacement for the tetrahedral HPO 4 unit with great success [9][10][11][12][13][14].…”

Phenomenon of Structural Transformation of Ethylenediamine- Oriented Synthesis of Microporous Cobalt Phosphate

“…17 在 400°C 焙烧γ-KCoPO4时, 它易于转 化为α-KCoPO4. 18 在研究乙二胺体系中合成的磷酸 钴微孔晶体(CoPO-en-1、 19,20 CoPO-en-2、 21 CoPOen-3、 22 CoPO-en-4)的过程中发现, 几种以乙二胺为 结构导向剂的磷酸钴微孔晶体可在同一个体系中 合成, 但这几种不同结构微孔晶体随水热合成条件 的改变可发生结构转化, 并且这几种结构在不同的 温度焙烧时均转化为同一结构的微孔晶体. 对这种 转化现象的研究有助于加强对微孔磷酸钴结构的 相似性及演化过程的认识与理解, 为其在锂离子电 池中的应用提供参考.…”