CO2‐fixation into carbonate anions for the construction of 3d‐4f cluster complexes with salen‐type Schiff base ligands: from molecular magnetic refrigerants to luminescent single‐molecule magnets

Abstract

Six new carbonate‐bridged Zn2Ln2 cluster complexes derived from salen‐type Schiff base ligands [H2La = N, N′‐bis(3‐methoxysalicylidene)‐1,3‐diaminopropane and H2Lb = N, N′‐bis(3‐methoxysalicylidene)‐ 1,2‐diaminoethane] have been synthesized. The bis‐imine chain in Schiff base ligands have an obvious influence on the cluster complexes' structures, magnetic and luminescence properties. The carbonate bridging ligand exactly comes from autoimmobilization of carbon dioxide, which may mediate ferromagnetic coupling between Ln3+ ions, favoring magnetocaloric effects and single molecule magnet (SMM) properties. Complexes Zn2Dy2(μ3‐CO3)2(La)2(NO3)2(MeOH)2 (1) and [Zn2Dy2(μ3‐CO3)2(Lb)2(NO3)2]·2MeOH (2) show field‐induced SMM properties; complexes Zn2Tb2(μ3‐CO3)2(La)2(NO3)2(MeOH)2 (3) and [Zn2Tb2(μ3‐CO3)2(Lb)2(NO3)2]·2MeOH (4) display both luminescence and field‐induced SMM behaviors; while complexes [Zn2Gd2(μ3‐CO3)2(La)2(NO3)2]·2MeOH (5) and [Zn2Gd2(μ3‐CO3)2(Lb)2(NO3)2]·2MeOH (6) exhibit medium magnetic entropy changes, which are candidates for cryogenic molecular magnetic refrigerants.