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Two C 3 ‐Symmetric Dy 3 III Complexes with Triple Di‐μ‐methoxo‐μ‐phenoxo Bridges, Magnetic Ground State, and Single‐Molecule Magnetic Behavior
Author(s) -
Hänninen Mikko M.,
Mota Antonio J.,
Aravena Daniel,
Ruiz Eliseo,
Sillanpää Reijo,
Camón Agustín,
Evangelisti Marco,
Colacio Enrique
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201402392
Subject(s) - chemistry , ground state , magnetization , ion , crystallography , trigonal bipyramidal molecular geometry , magnetic moment , paramagnetism , magnetic anisotropy , atomic physics , condensed matter physics , magnetic field , physics , crystal structure , organic chemistry , quantum mechanics
Two series of isostructural C 3 ‐symmetric Ln 3 complexes Ln 3 ⋅ [BPh 4 ] and Ln 3 ⋅ 0.33[Ln(NO 3 ) 6 ] (in which Ln III =Gd and Dy) have been prepared from an amino‐bis(phenol) ligand. X‐ray studies reveal that Ln III ions are connected by one μ 2 ‐phenoxo and two μ 3 ‐methoxo bridges, thus leading to a hexagonal bipyramidal Ln 3 O 5 bridging core in which Ln III ions exhibit a biaugmented trigonal‐prismatic geometry. Magnetic susceptibility studies and ab initio complete active space self‐consistent field (CASSCF) calculations indicate that the magnetic coupling between the Dy III ions, which possess a high axial anisotropy in the ground state, is very weakly antiferromagnetic and mainly dipolar in nature. To reduce the electronic repulsion from the coordinating oxygen atom with the shortest DyO distance, the local magnetic moments are oriented almost perpendicular to the Dy 3 plane, thus leading to a paramagnetic ground state. CASSCF plus restricted active space state interaction (RASSI) calculations also show that the ground and first excited state of the Dy III ions are separated by approximately 150 and 177 cm −1 , for Dy 3 ⋅ [BPh 4 ] and Dy 3 ⋅ 0.33[Dy(NO 3 ) 6 ], respectively. As expected for these large energy gaps, Dy 3 ⋅ [BPh 4 ] and Dy 3 ⋅ 0.33[Dy(NO 3 ) 6 ] exhibit, under zero direct‐current (dc) field, thermally activated slow relaxation of the magnetization, which overlap with a quantum tunneling relaxation process. Under an applied H dc field of 1000 Oe, Dy 3 ⋅ [BPh 4 ] exhibits two thermally activated processes with U eff values of 34.7 and 19.5 cm −1 , whereas Dy 3 ⋅ 0.33[Dy(NO 3 ) 6 ] shows only one activated process with U eff =19.5 cm −1 .