Occurrence of a Rare 4⁹·6⁶ Structural Topology, Chirality, and Weak Ferromagnetism in the [NH₄][M^II(HCOO)₃] (M = Mn, Co, Ni) Frameworks

Abstract

We report the synthesis, crystal structures, thermal, IR, UV-vis, and magnetic properties of a series of divalent transition metal formates, [NH4][M(HCOO)3], where M = divalent Mn, Co, or Ni. They crystallize in the hexagonal chiral space group P6(3)22. The structure consists of octahedral metal centers connected by the anti-anti formate ligands, and the ammonium cations sit in the channels. The chiral structure is a framework with the rarely observed 49.66 topology, and the chirality is derived from the handedness imposed by the formate ligands around the metals and the presence of units with only one handedness. The thermal properties are characterized by a decomposition at ca. 200 degrees C. The three compounds exhibit an antiferromagnetic ground state at 8.4, 9.8, and 29.5 K for Mn, Co, and Ni, respectively. The last two display a weak spontaneous magnetization due to a small canting of the moments below the critical temperature, and the Co compound shows a further transition at lower temperatures. The isothermal magnetizations at 2 K show spin-flop fields of 600 Oe (Mn), 14 kOe (Co), and above 50 kOe (Ni) and a small hysteresis with a remnant magnetization of 25 cm3 G mol(-1) (Co) and 50 cm3 G mol(-1) (Ni) and coercive field of 400 Oe (Co) and 830 Oe (Ni).

Hierarchical cobalt-formate framework series with (412⋅63)(49⋅66)n (n = 1–3) topologies exhibiting slow dielectric relaxation and weak ferromagnetism

“…34 Finally, the couplings (J/k B ) between Co 2+ ions via the anti-anti formato bridge, estimated from J/k B = 3Θ/[2zS(S + 1)], 33 are −4.0 (bnCo), −3.6 (dptaCo), and −4.3 K (tptaCo), similar to those of Co-AMFFs with anti-anti HCOO linkages reported before. 8,11,13,14,18,19 In conclusion, the results of varying the length of linear polyammonium cations demonstrate the progressive structure-directing effect in the formation of binodal (4 12 · 6 3 )(4 9 · 6 6 ) n (n = 1, 2, and 3) topologies in Co AMFFs. This progressive development is a rare observation in the field of transition-metal perovskites chemistry.…”

“…8 The framework structures could be easily controlled, or templated, by the shape, size, and charge of the ammoniums. For mono-ammoniums (AH + ), the small ones [9][10][11][12][13][14] 20 and the framework topology is binodal (4 12 · 6 3 )(4 9 · 6 6 ). Lanthanide 21,22 and uranyl 23 AMFFs have also been reported to show more complicated structures and framework topologies.…”

“…Lanthanide 21,22 and uranyl 23 AMFFs have also been reported to show more complicated structures and framework topologies. The physics of AMFFs are found abundant, thanks to the combination of ammonium, metal ion, and the formate bridge, which provide the [9][10][11][12][13][14][15][16][17][18] especially in the perovskites. Some of them even have high phase transition temperatures comparable to the ferroelectric oxides.…”

“…Some of them even have high phase transition temperatures comparable to the ferroelectric oxides. 10,11,14 Magnetic/dielectric relaxation and temperature/pressure-induced structural transitions have been observed in several lanthanide AMFFs. 21,22 The niccolite dmaFeFe displayed para-to antiferro-electric transition of unusual structural alternations and Néel N-Type ferrimagnetism.…”

Hydrothermal synthesis and crystal structure of a new coordination polymer: [Zn1(deta)(btec)(H2O)2]n

“…During the 90's, multifunctional benzene carboxylic acids have been successfully employed for the preparation of a new class of metal-organic frameworks [1][2][3][4][5] . The use of multidentate organic ligands and metal ions to construct metal-organic frameworks (MOFs) has attracted much attention 6 due to their fascinating molecular and/or supramolecular structural diversity 7 and enormous potential applications as new functional material in gas storage and separation, magnetic materials, ion-exchange [8][9][10][11][12][13][14] , catalysis 15 , etc. The rigid aromatic polycarboxylate ligands, such as 1,4-benzenedicarboxylate (1,4-bdc) 16-17 , 1,3-benzenedicarboxylate (m-bdc) [18][19] , 1,2-benzenedicarboxylate (1,2-bdc) [20][21] , 1,3,5-benzenetricarboxylate (1,3,5-btc) [22][23] , have been widely used as bridging ligands for the design and synthesis of porous materials with robust structures and high porosity.…”