Cryogenic magneto-caloric effect and magneto-structural correlations in carboxylate-bridged Gd(iii) compounds

Abstract

Two new infinite coordination chain compounds [Gd(CH3CO2)3(dmf)]∞ (1) and {[Gd(HO(CH2)3CO2)3(H2O)]·H2O}∞ (2) have been obtained attempting to modify a prototype molecular cooler. The structures of both compounds as determined by single-crystal X-ray diffraction are reported, together with a detailed study of their magnetic and thermal properties, describing for both compounds a large magneto-caloric effect. The dominant ferromagnetic interaction present in 2 clearly favours this material at low applied magnetic fields, with respect to 1 that exhibits antiferromagnetic interactions. Magneto-structural correlations of the sign and strength of the magnetic interactions are derived for carboxylato-bridged Gd(III) systems.

A magnetocaloric composite based on molecular coolers and carbon nanotubes with enhanced thermal conductivity

“…In agreement with previous studies, [8] bulk-[Gd 2 ac] is characterized by a weak ferromagnetic coupling (J = 0.07 K). We find a weak coupling strength also for the [Gd 2 ac] molecules in the composite material, though the s Gd1 -s Gd2 coupling is here antiferromagnetic with J = -0.05 K. Given the extreme sensitivity of the exchange coupling in carboxylicbridged pairs of Gd(III) ions to slight changes of the bridge structural parameters, [22] it is not surprising that the s Gd1 -s Gd2 coupling in the [Gd 2 ac] molecules changes its sign when going from bulk crystalline form to the grafting onto MWCNTs in the composite material. Figure S9, ∆S m curves in the range 3-9 K are determined for applied field changes ∆B from 1 to 5 T. The values so-obtained ( Figure S10), for example -∆S m = 24.7 J kg -1 K -1 at T = 3 K for ∆B = 3 T, are the same as those for bulk-[Gd 2 ac], confirming that the molecules grafted on the MWCNTs are similar to those in bulk-[Gd 2 ac], and that they maintain intact their large MCE.…”

Highly luminescent mixed-ligand bimetallic lanthanoid(iii) complexes for photovoltaic applications

“…Gd 3+ dinuclear compounds connected by carboxylate bridges may exhibit different bridging modes, described as A, B and C according to Baggio et al 59,63 Several experimental and theoretical magneto-structural studies have been performed in this kind of compounds, but a clear correlation related to a specific parameter has not been found yet. 64 Nevertheless, the most important parameters are the intermetallic Gd 3+ ⋯Gd 3+ distances, and the θ and φ parameters (Fig. S6 †).…”

Coordination‐Cluster‐Based Molecular Magnetic Refrigerants

“…Replacing the coordinated water molecules and acetate ligands of 21 ,40 by DMF and Hhbc, Roubeau et al obtained two infinite 1D chain CPs, 51 and 52 , respectively 52. The maximum –Δ S m values for an applied field of 70 kOe at 1.8 K reach 43.3 J kg −1 K −1 for 51 and 37.1 J kg −1 K −1 for 52 .…”

“…Among Ln ions, the Gd III ion is usually chosen to construct molecular magnetic refrigerants; this may be attributes to the Gd III ion having a large single‐ion spin ( S =7/2) and negligible anisotropy, resulting from the lack of orbital contribution. Furthermore, the coupled interactions between Gd III ions are always weak, which is fit for acquiring a large MCE to work as an ideal molecular magnetic refrigerant (Tables and ) 25,27,39–57…”

“…Compared with discrete 4f‐metal‐cluster‐based molecular magnetic refrigerants,39–50 the numbers and types of pure 4f‐metal‐cluster‐based extended structures serving as molecular magnetic refrigerants are greater (Table );51–67 this may be because Ln ions possess various coordinated geometries and high coordination numbers, as well as minimal stereochemical preferences.…”