The fruitful introduction of chirality and control of absolute configurations in molecular magnets

Abstract

In this critical review, it is shown how the introduction of chirality and the control of the absolute configurations of chiral elements in molecular magnets allow obtaining enantiopure chiral magnets (ECM), an archetype of multifunctional materials. This task has been recognised as a major challenge for both chemists and physicists of molecular magnetism. To reach this goal, the former have combined the rational approaches towards molecular-based magnets and of enantiopure metal-organic frameworks. They have used enantiopure stable radicals, ligands from the chiral pool, enantiopure coligands associated with achiral connectors or enantioselective self-assembly to successfully reach their synthetic targets. They were motivated by the will to obtain suitable systems for the experimental demonstration of the influence of enantiomeric purity on the physico-chemical properties. This influence can be found in the magnetic properties themselves but, most interestingly, in the coexistence and interaction between the properties arising from controlled non-centrosymmetry. Thus the combination of natural circular dichroism, second harmonic generation or ferroelectricity with long-range magnetic ordering can give birth to new properties like magneto-chiral dichroism, magnetisation induced second harmonic generation or multiferroicity. The two former synergetic effects have already been demonstrated in enantiopure chiral magnets. The third one remains a challenging target that can be reached by adapting strategies developed towards enantiopure molecular ferroelectrics (119 references).

Diversity of Coordination Modes, Structures, and Properties of Chiral Metal–Organic Coordination Complexes of the Drug Voriconazole

“…[7,8] In general, the use of enantiopure chiral organic ligands as starting materials is considered, undeniably, to be one of the most effective strategies for generating chiral MOFs. [9][10][11][12] Some enantiopure organic building blocks, such as d-camphoric acid, l-aspartic acid, l-glutamic acid, l-tartric acid, l-lactic acid, and organic ligands containing chiral polypyridyl and polycarboxylate groups, have already been widely used to obtain artificial chiral architectures. [13,14] However, there are only a few examples of crystals constructed from drug ligands.…”

Disproportionation of Achiral Nickel(II) Centers into Two Kinds of Chiral Nickel(II) Centers Caused by an Achiral Diimine Ligand

“…[2][3][4][5][6] In recent years, chiral coordination compounds have received increased attention because of their potential applications in asymmetric catalysis, nonlinear optics, sensors, and multifunctional materials, [7][8][9][10] as well as due to their fundamental significance in modern stereochemistry. [11] The most representative approach for introducing chirality in coordination compounds is the chelation of three bidentate ligands to a metal center, which gives rise to a metal octahedron with either the D or the L chiral configuration.…”

Magnetic diagnostics using the third-harmonic magnetic response for a molecule-based magnet networked by a single chiral ligand

“…A strategy for the creation of a structurally chiral magnet is a chemical approach relying upon a spontaneous resolution process using proper bridging ligands. 1 In the Prussian-Blue family of molecule-based magnets, the intentional construction of crystallographic chirality with high dimensionality, using the association of a chiral organic ligand, has been successfully performed. 2,3 If the target material could have large spontaneous magnetic moments accompanying the breaking of the time reversal symmetry, the magnetic second-harmonic generation (MSHG) 4-6 and the magneto-chiral dichroism (MChD) effects 7-10 would be quite promising for industrial applications.…”