title: A thermal spin transition in [Co(bpy)3][LiCr(ox)3] (ox = C2O4(2-); bpy = 2,2'-bipyridine).
abstract: In the three-dimensional oxalate network structures [M(II)(bpy)3][M(I)-M(III)(ox)3] (ox= C2O4(2-); bpy = 2,2'-bipyridine) the negatively charged oxalate backbone provides perfect cavities for tris-bipyridyl complex cations. The size of the cavity can be adjusted by variation of the metal ions of the oxalate backbone. In [Co(bpy)3][NaCr(ox)3], the [Co(bpy)3]2 + complex is in its usual 4T1(t2g5e(g)2) high-spin ground state. Substituting Na+ by Li+ reduces the size of the cavity. The resulting chemical pressure destabilises the high-spin state of [Co(bpy)3]2+ to such an extent that the 2E(t2g6e(g)1) low-spin state becomes the actual ground state. As a result. [Co(bpy)3][LiCr(ox)3] becomes a spin-crossover system, as shown by temperature-dependent magnetic susceptibility measurements and single-crystal optical spectroscopy, as well as by an X-ray structure determination at 290 and 10 K.
authors.affiliation: Departement für Chemie und Biochemie, Universität Bern, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Sieber
authors.forename: S
authors.initials: S
authors.lastname: Decurtins
authors.forename: H
authors.initials: H
authors.lastname: Stoeckli-Evans
authors.forename: C
authors.initials: C
authors.lastname: Wilson
authors.forename: D
authors.initials: D
authors.lastname: Yufit
authors.forename: J A
authors.initials: JA
authors.lastname: Howard
authors.forename: S C
authors.initials: SC
authors.lastname: Capelli
authors.forename: A
authors.initials: A
authors.lastname: Hauser