%0 Journal Article %A Das, Chinmoy %A Upadhyay, Apoorva %A Ansari, Kamal Uddin %A Ogiwara, Naoki %A Kitao, Takashi %A Horike, Satoshi %A Shanmugam, Maheswaran %D 2018 %T Lanthanide-Based Porous Coordination Polymers: Syntheses, Slow Relaxation of Magnetization, and Magnetocaloric Effect %U https://acs.figshare.com/articles/journal_contribution/Lanthanide-Based_Porous_Coordination_Polymers_Syntheses_Slow_Relaxation_of_Magnetization_and_Magnetocaloric_Effect/6275882 %R 10.1021/acs.inorgchem.8b00720.s001 %2 https://ndownloader.figshare.com/files/11477336 %K powder X-ray diffraction %K EXAFS %K lattice %K L 1 %K Lanthanide-Based Porous Coordination Polymers %K PCP %K H 2 O %K measurement %K TG-MS %K water molecules %K Gd %K lanthanide complexes 2 %K formula %K n H 2 O %K Magnetization relaxation dynamics %K cm %K Ln 2 %K solvated water molecule %K PXRD %K ab initio calculations %K solvated water molecules %K TGA %K Dy %K XANES %K MCE %X Two lanthanide-containing structurally analogous porous coordination polymers (PCPs) have been isolated with the general molecular formula [Ln2(L1)2(H2O)4(ox)]n.4nH2O (where L1 = fumarate, ox = oxalate; Ln = Dy (1), Gd (2)). Thermogravimetric analysis (TGA) and TG-MS measurements performed on 1 and 2 suggest that not only the solvated water molecules in the crystal lattice but also the four coordinated water molecules on the respective lanthanides in 1 and 2 are removed upon activation. Due to the removal of the waters, 1 and 2 lost their crystallinity and became amorphous, as confirmed by powder X-ray diffraction (PXRD). We propose the molecular formula [Ln2(L1)2(ox)]n for the amorphous phase of 1 and 2 (where Ln = Dy (1′), Gd (2′)) on the basis of XANES, EXAFS, and other experimental investigations. Magnetization relaxation dynamics probed on 1 and 1′ reveal two different relaxation processes with effective energy barriers of 53.5 and 7.0 cm–1 for 1 and 45.1 and 6.4 cm–1 for 1′, which have been rationalized by detailed ab initio calculations. For the isotropic lanthanide complexes 2 and 2′, magnetocaloric effect (MCE) efficiency was estimated through detailed magnetization measurements. We have estimated −ΔSm values of 52.48 and 41.62 J kg1– K–1 for 2′ and 2, respectively, which are one of the largest values reported for an extended structure. In addition, a 26% increase in −ΔSm value in 2′ in comparison to 2 is achieved by simply removing the passively contributing (for MCE) solvated water molecule in the lattice and coordinated water molecules. %I ACS Publications