Tricarboxylate-based GdIII coordination polymers exhibiting large magnetocaloric effects†
Abstract
Two GdIII coordination polymers with the formula [Gd(cit)(H2O)]∞ (1) and [Gd(nta)(H2O)2]∞ (2) (H4cit = citric acid, H3nta = nitrilotriacetic acid) have been successfully prepared under hydrothermal conditions. Complex 1 exhibits a three-dimensional (3D) structure based on carboxylate-bridged layers, while complex 2 is a double-layer structure containing eight-coordinated GdIII. Magnetic investigations reveal that weak antiferromagnetic couplings between adjacent GdIII ions in both 1 and 2 with different Weiss values result in large cryogenic magnetocaloric effects. It is notable that the maximum entropy changes (−ΔSmaxm) of 1 and 2 reach 31.3 J kg−1 K−1 and 32.2 J kg−1 K−1 at 2 K for a moderate field change (ΔH = 3 T), and a remarkable −ΔSmaxm (41.5 J kg−1 K−1 for 1 and 42.0 J kg−1 K−1 for 2) could be obtained for ΔH = 7 T.