Transition‐Metal Dependent Cation Disorder in the Chiral Cubic AB(HCO₂)₃ Metal‐Organic Frameworks (A = Li or Na, B = Mn or Co)

Abstract

We dedicate this, the first work from our group at the University of Kent, to Professor Anthony Cheetham on the occasion of his 70 th birthday.Abstract: This study examines the crystal structures of the AB(HCO2)3 (where A = Li or Na and B = Mn or Co) metal-organic frameworks, which we find to adopt a chiral cubic P213 structure. This shows that the Li containing formates are isostructural with their Na analogues, extending the phase stability of this chiral architecture. The Mn containing compounds have a magnetic sublattice similar to -Mn, long of interest due to its highly frustrated antiferromagnetic coupling. In contrast the Co formates appear to have partially disordered alkali and transition metal cations, which prevents the formation of a clean -Mn-like magnetic sublattice. We have also reexamined the magnetic properties of NaMn(HCO2)3 finding it to be a simple paramagnet down to 2 K with only weak antiferromagnetic coupling.

Tilting and twisting in a novel perovzalate, K3NaMn(C2O4)3

“…It is also of note that a highersymmetry version of this structure type, space group Ia3 ̅ d, is also feasible. This requires the two distinct octahedral cation sites to become equivalent, leading to a bcs net, 18 which may be possible either by disorder of the monovalent/divalent cations at the Na and Mn sites, which has been reported in related systems with formate linkers, 26 or by deliberate design of a composition containing exclusively monovalent or divalent cations at the octahedral sites, with consequent charge balance being required at the K-sites, or by some other mechanism. Analysis of compound 1 in two space groups based on single crystal and powder XRD confirmss unambiguously the Ia3 ̅ structure rather than Ia 3 ̅ d (ESI †).…”

Skyrmion Lattices in Chiral Metal–organic Frameworks

“…netic with no strong spin-orbit coupling, and hence is unlikely to support a magnetic skyrmion phase. 29,30 But while magnetic interactions in MOFs are notoriously weak, the effective interactions between molecules contained within their pores can be strong indeed-such is the basis, after all, of the 'crystalline sponge' concept 31,32 and the origin of orientational order/disorder transitions in e.g. hybrid perovskites.…”

Skyrmion Lattices in Chiral Metal–organic Frameworks

“…28 Like many MOFs, this material is weakly antiferromag- netic with no strong spin-orbit coupling, and hence is unlikely to support a magnetic skyrmion phase. 29,30 But while magnetic interactions in MOFs are notoriously weak, the effective interactions between molecules contained within their pores can be strong indeed-such is the basis, after all, of the 'crystalline sponge' concept 31,32 and the origin of orientational order/disorder transitions in e.g. hybrid perovskites.…”