Polyoxotungstates now also with pentagonal units: supramolecular chemistry and tuning of magnetic exchange in {(M)M5}12V30 Keplerates (M = Mo, W)

Abstract

The deliberate synthesis of the Keplerate [K(20) subset{(W)W(5)O(21)(SO(4))}(12)(VO)(30)(SO(4))(H(2)O)(63)](18-) with 20 pores all closed by K(+) in a supramolecular fashion proves that it is possible to follow new routes in polyoxotungstate chemistry based on pentagonal {(W)W(5)}-type units and to tune magnetic exchange couplings in {(M)M(5)}(12)M'(30) type Keplerates.

Tunnel-diode resonator and nuclear magnetic resonance studies of low-dimensional magnetic and superconducting systems

“…[66]. The temperature dependence of the magnetic susceptibility χ = M/H for fixed H = 0.1 T was measured in a temperature range of 1.9…”

“…The vanadium-oxygen distances which bridge to neighboring vanadium ions vary by about ±0.02 whereas the distances to the two remaining oxygen sites vary by 0.2Åwhen comparing the various vanadium coordination spheres (see crystal structure in [66]). We speculate that this is one source of the distribution of exchange couplings discussed above.…”

“…Carlo method (QMC) on choosing the antiferromagnetic nearest-neighbor exchange constant J = -57.5 K and the spectroscopic splitting factor g = 1.95 [66]. These numerical values are associated with a Heisenberg Hamiltonian written as…”

Magnetization and spin dynamics of the spinS=12hourglass nanomagnet Cu5(OH)

“…21,22 The spin triangle is the most elementary unit for highly frustrated magnetism, 23 while its chirality may induce a finite magnetoelectric coupling, 24,25 and may also be used as a qubit. 26 In molecular magnetism, the spin triangle is common in many compounds, 1 35 which host highly frustrating kagome-like physics. 36 The distinct feature of the present compound is the strong distortion of its regular spin triangles, featuring by gray shading) through the NIPA ligand molecules, into a rigid three-dimensional metal-organic framework, with the shortest distance of 8.6Å between the magnetic units.…”

Determination of exchange energies in the sawtooth spin ring {Mo75V20} by ESR

“…[1][2][3][4][5][6][7][8][9][10] In these nanosized molybdate or tungstate-based molecules, 30 magnetic ions are located on the 30 vertices of an icosidodecahedron and are antiferromagnetically coupled, resulting in triangular and pentagonal networks. As a result, this leads to a strongly frustrated cluster with a huge number of quantum states.…”