The effect of the electronic structure and flexibility of the counterions on magnetization relaxation in [Dy(L)2(H2O)5]3+ (L = phosphine oxide derivative) pentagonal bipyramidal SIMs. Díaz Ortega, Ismael Francisco Herrera Martínez, Juan Manuel Dey, Sourav Nojiri, Hiroyuki Rajaraman, Gopalan Colacio Rodríguez, Enrique Single Molecule Magnets Molecular Magnetism Dysprosium Pentagonal bipyramidal geometry We report here a new DyIII-SIM [Dy(OPCy3)2(H2O)5](CF3SO3)3·2OPCy3 (OPCy3 = triclohexylphosphine oxide) with pentagonal bipyramidal geometry, which exhibits a blocking temperature TB = 8.5 K and an anisotropy barrier Ueff = 562 K. Ab initio calculations show that this complex exhibits the largest Ucalc = 732 K among the DyIII-SIMs complexes containing the [Dy(L)2(H2O)5]3+ (L = phosphine oxide derivative) cationic unit, which is essentially due to the electronic effects of the triflate anion that increase the charge difference between the oxygen atoms of the ligands L coordinated in axial positions and those belonging to the equatorial water molecules. This charge difference enhancement, which is also reflected in a larger difference between the corresponding Dy-O distances (), appears to be the driving force to push up the Ucalc value. The comparative smaller experimental Ueff value observed for this compound has been justified by the flexibility of the structural network due to the size of the triflate counteranions. The absence of a clear correlation between TB and Ueff (or Ucalc) suggests the involvement of Raman and QTM mechanism in the magnetization relaxation process. 2026-01-16T10:47:25Z 2026-01-16T10:47:25Z 2020 journal article Inorg. Chem. Front., 2020, 7, 689 https://hdl.handle.net/10481/109795 10.1039/c9qi01412h eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional Royal Society of Chemistry, Chinese Chemical Society