title: Reversible solvatomagnetic switching in a spongelike manganese(II)-copper(II) 3D open framework with a pillared square/octagonal layer architecture.
abstract: The concept of "molecular magnetic sponges" was introduced for the first time in 1999 by the creative imagination of the late Olivier Kahn. It refers to the exotic spongelike behavior of certain molecule-based materials that undergo a dramatic change of their magnetic properties upon reversible dehydration/rehydration processes. Here we report a unique example of a manganese(II)-copper(II) mixed-metal-organic framework of formula [Na(H(2)O)(4)](4)[Mn(4){Cu(2)(mpba)(2)(H(2)O)(4)}(3)]·56.5H(2)O (1) (mpba=N,N'-1,3-phenylenebis(oxamate)). Compound 1 possesses a 3D Mn(II)(4)Cu(II)(6) pillared layer structure with mixed square and octagonal pores of approximate dimensions 1.2×1.2 nm and 2.1×3.0 nm, respectively, hosting a large amount of crystallization H(2)O molecules and hydrated Na(I) countercations as guests. It reversibly switches from a crystalline hydrated phase with long-range ferromagnetic ordering at a rather high critical temperature (T(c)) of 22.5 K to an amorphous dehydrated phase with T(c) as low as 2.3 K, which is accompanied by a breathing-type dynamic effect involving a large crystal volume (ca. 45%) and color changes after water desorption/adsorption. The combination of both the open-framework structure and the spongelike optical, mechanical, and magnetic switching behavior in this new class of oxamato-based porous magnets offers fascinating possibilities in designing multifunctional materials for host-guest molecular sensing.
authors.affiliation: Instituto de Ciencia Molecular (ICMol), Universitat de València, 46980 Paterna, València, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Ferrando-Soria
authors.forename: Rafael
authors.initials: R
authors.lastname: Ruiz-García
authors.forename: Joan
authors.initials: J
authors.lastname: Cano
authors.forename: Salah-Eddine
authors.initials: SE
authors.lastname: Stiriba
authors.forename: Julia
authors.initials: J
authors.lastname: Vallejo
authors.forename: Isabel
authors.initials: I
authors.lastname: Castro
authors.forename: Miguel
authors.initials: M
authors.lastname: Julve
authors.forename: Francesc
authors.initials: F
authors.lastname: Lloret
authors.forename: Pedro
authors.initials: P
authors.lastname: Amorós
authors.forename: Jorge
authors.initials: J
authors.lastname: Pasán
authors.forename: Catalina
authors.initials: C
authors.lastname: Ruiz-Pérez
authors.forename: Yves
authors.initials: Y
authors.lastname: Journaux
authors.forename: Emilio
authors.initials: E
authors.lastname: Pardo