Polar Materials with Isolated V⁴⁺ S = 1/2 Triangles: NaSr₂V₃O₃(Ge₄O₁₃)Cl and KSr₂V₃O₃(Ge₄O₁₃)Cl

Abstract

Crystals of ASr 2 V 3 O 3 (Ge 4 O 13 )Cl, A = Na, K, were synthesized from high-temperature hydrothermal brines, and their structure and magnetic properties were investigated. These materials present a unique combination of a salt inclusion lattice, a polar crystal structure, and isolated V 4+ (S = 1/2) trimer magnetic clusters. The structures consist of a trimeric V 3 O 13 unit based on V 4+ (S = 1/2), having rigorous 3fold symmetry with a short V−V separation of 3.325(3) Å. The trinuclear V 4+ units are formed by three edge shared VO 6 octahedra sharing a central μ 3 -oxygen atom, which also imparts a polar sense on the structure. The V 3 O 13 units are isolated from one another by tetranuclear Ge 4 O 13 units, which are similarly arranged in a polar fashion, providing a unique opportunity to study the magnetic behavior of this triangular d 1 system as a discrete unit. Magnetization measurements indicate spin-1/2 per V atom at high temperature, and spin-1/2 per V 3 trimer at low temperature, where two V moments in each triangle are antiferromagnetically aligned and the third remains paramagnetic. The crossover between these two behaviors occurs between 20 and 100 K and is well-described by a model incorporating strong antiferromagnetic intra-trimer interactions and weak but nonzero inter-trimer interactions. More broadly, the study highlights the ability to obtain new materials with interesting structure−property relationships via chemistry involving unconventional solvents and reaction conditions.

Sodium Transition Metal Vanadates from Hydrothermal Brines: Synthesis and Characterization of NaMn4(VO4)3, Na2Mn3(VO4)3, and Na2Co3(VO4)2(OH)2

“…This rich chemistry makes the vanadates an almost ideal testbed for the study of brine fluids on new material formation. Thus far we have investigated rubidium‐, cesium‐, strontium‐, and barium‐based halide brines with transition metal vanadates under hydrothermal conditions , , . In some cases we have observed halide incorporation into the lattice, such as in Ba 5 Mn 3 (V 2 O 7 ) 3 (OH,Cl)Cl 3 , Ba 2 Mn(V 2 O 7 )(OH)Cl, and Cs 3 Mn(VO 3 ) 4 Cl .…”

“…These vanadate oxyanions can coordinate magnetically active first‐row transition metals (i.e. Mn 2+/3+ , Co 2+ , Fe 2+/3+ ) to generate a rich assortment of structurally diverse and magnetically interesting compounds . These materials are generally synthesized at relatively high temperatures using traditional solid‐state techniques, such as melts or fluxes , .…”

Color-tunable luminescence and temperature sensing properties of Bi3+/Sm3+ or Bi3+/Eu3+ codoped Ba2Gd2Ge4O13 phosphors

“…13 In the present study, we focus on the structural characterization and luminescence properties of Ba 2 Gd (RE = Pr, Nd, Eu, Gd, Dy, Y). [14][15][16][17][18][19][20][21] Recently, several research groups have succeeded in creating a number of efficient phosphors based on the Ba 2 RE 2 Ge 4 O 13 family.…”

“…To date only a few germanates containing a similar type of building blocks are known, among them Na 4 Sc 2 Ge 4 O 13 , Cu 2 Sc 2 Ge 4 O 13 , Cu 2 Fe 2 Ge 4 O 13 , ASr 2 V 3 O 3 (Ge 4 O 13 )Cl (A = Na and K) and Ba 2 RE 2 Ge 4 O 13 (RE = Pr, Nd, Eu, Gd, Dy, Y). 14–21…”

Dimensionality Effect of the “Free-Oxygen” Motif on the Crystal Field Splitting in Rare-Earth Crystals

“…Crystal field theory (CFT) explains how the degeneracy of 3d and 4f electron orbitals is broken by the electrostatic field produced by the surrounding charge distribution from the neighbor anions . It plays an important role in the optical spectra, magnetic, and Jahn–Teller distortion of materials doped with transition metal and lanthanide ions. − Since initially proposed by Bethe and van Vleck in 1930s, the Coulomb interaction between the central ion and surrounding ligands makes a dominant contribution to the energy level difference between the high- and low-energy states. This energy splitting is sensitive to the nature of the metal ion and ligands concurrently, especially the type and arrangement of the surrounding ligands. , In general, the magnitude of splitting depends on the symmetry and position of the ligands as well as on the spin–orbit coupling of the lanthanide ions.…”