title: Fluoride-bridged {Gd(III)3M(III)2} (M = Cr, Fe, Ga) molecular magnetic refrigerants.
abstract: The reaction of fac-[M(III)F3(Me3tacn)]⋅x H2O with Gd(NO3)3⋅5H2O affords a series of fluoride-bridged, trigonal bipyramidal {Gd(III)3M(III)2} (M = Cr (1), Fe (2), Ga (3)) complexes without signs of concomitant GdF3 formation, thereby demonstrating the applicability even of labile fluoride-complexes as precursors for 3d-4f systems. Molecular geometry enforces weak exchange interactions, which is rationalized computationally. This, in conjunction with a lightweight ligand sphere, gives rise to large magnetic entropy changes of 38.3 J kg(-1)  K(-1) (1) and 33.1 J kg(-1)  K(-1) (2) for the field change 7 T→0 T. Interestingly, the entropy change, and the magnetocaloric effect, are smaller in 2 than in 1 despite the larger spin ground state of the former secured by intramolecular Fe-Gd ferromagnetic interactions. This observation underlines the necessity of controlling not only the ground state but also close-lying excited states for successful design of molecular refrigerants.
authors.affiliation: Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen (Denmark).
authors.forename: Kasper S
authors.initials: KS
authors.lastname: Pedersen
authors.forename: Giulia
authors.initials: G
authors.lastname: Lorusso
authors.forename: Juan José
authors.initials: JJ
authors.lastname: Morales
authors.forename: Thomas
authors.initials: T
authors.lastname: Weyhermüller
authors.forename: Stergios
authors.initials: S
authors.lastname: Piligkos
authors.forename: Saurabh Kumar
authors.initials: SK
authors.lastname: Singh
authors.forename: Dennis
authors.initials: D
authors.lastname: Larsen
authors.forename: Magnus
authors.initials: M
authors.lastname: Schau-Magnussen
authors.forename: Gopalan
authors.initials: G
authors.lastname: Rajaraman
authors.forename: Marco
authors.initials: M
authors.lastname: Evangelisti
authors.forename: Jesper
authors.initials: J
authors.lastname: Bendix
keywords: density functional calculations; fluoride ligands; lanthanides; magnetic properties; magnetic refrigeration