Three caesium‐bearing borophosphates, Cs[BP2O6(OH)2] (I), Cs0.51Mn1.17(H2O)2[BP2O8]·0.45H2O (II) and CsMn[BP2O8(OH)] (III), were synthesized by a hydrothermal method at 473–523 K. Their crystal structures have been studied by means of single‐crystal X‐ray diffraction; all three structures comprise borophosphate chain anions with a B:P ratio of 1:2. The unique construction of (I) is based on four‐membered‐ring chains running parallel to the [010] direction. These protonated borophosphate chains are linked via hydrogen‐bond interactions to form a 3D framework with caesium cations incorporated. (II) is the first Cs and Mn2+,Mn3+ member of a known family characterized by [BP2O8]∞ helical chains running along [001]. These chains are connected through MnO4(H2O)2 octahedra to form a 3D framework. The caesium cations are disordered over two independent positions in the channels, which they occupy together with water molecules. An additional MnO2(H2O)3 bipyramid statistically shares a common edge and two corners with three main Mn octahedra to form tetrameric clusters. The topological relation between the chain anionic fragments of (I) and (II) as well as the structural relation between (I) and previously studied boro‐ and berillophosphates are discussed. Compound (III) presents the first Mn member of the AIMIII[BP2O8(OH)] family and is characterized by a 3D framework built by open‐branched borophosphate chains and MnO5 semi‐octahedra sharing vertices. The measurements of thermodynamic properties, i.e. magnetization M and specific heat Cp, to 2 K and 30 T, provide evidence that (II) orders antiferromagnetically at the Néel temperature TN = 4.6 K and exhibits a plateau‐like feature under the action of an external magnetic field accompanied by a pronounced magnetocaloric effect.

We synthesized single crystals of Na 0.55 Ni 6 (OH) 3 (H 0.61 PO 4 ) 4 (I) and polycrystals of (Na, Ni) 0.64 Ni 5.68 (OH) 3 (H 0.67 PO 4 ) 4 (II) with ellenbergeritelike structures using the hydrothermal method. The phases crystallize in the hexagonal space group P6 3 mc with the following unit cell parameters: a = 12.5342(1) Å, c = 4.9470(1) Å, and V = 673.08(2) Å 3 for I; a = 12.4708(2) Å, c = 4.9435(2) Å, and V = 665.82(2) Å 3 for II; and Z = 2. Their crystal structures are based on a 3D framework built from NiO 6 octahedra and PO 4 tetrahedra. The difference between I and II lies in the way the structural channels are filled along the [001] direction. These channels accommodate segments of Na-and (Na, Ni)centered chains of face-sharing octahedra in the structures I and II, respectively. The magnetic susceptibility χ and the specific heat C p evidence pronounced low-dimensional magnetic behavior at elevated temperatures and the formation of the weakly ferromagnetic long-range order at T N I = 61 K and T N II = 63 K. Analysis of the χ(T) data within both chain and dimer spin models allows the estimation of the leading exchange interaction parameters in the compounds under study.

Two novel bismuth oxosalts, β-Bi3O3(VO4) and KBi5O5(PO4)2, synthesized hydrothermally crystallize in the triclinic space group P1̅ with a = 5.7337 (6), b = 7.1029 (8), c = 9.298 (1) Å,...

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