TY - JOUR
T1 - Designing a Dy2 Single-Molecule Magnet with Two Well-Differentiated Relaxation Processes by Using a Nonsymmetric Bis-bidentate Bipyrimidine- N-Oxide Ligand
T2 - A Comparison with Mononuclear Counterparts
AU - Díaz-Ortega, Ismael F.
AU - Herrera, Juan Manuel
AU - Aravena, Daniel
AU - Ruiz, Eliseo
AU - Gupta, Tulika
AU - Rajaraman, Gopalan
AU - Nojiri, H.
AU - Colacio, Enrique
N1 - Funding Information:
I.F.D.-O., J.M.H., E.R., and E.C. are grateful to the Ministerio de Economiá y Competitividad and EU Feder Funds (Projects CTQ2014-56312-P and CTQ2015-64579-C3-1-P), the Junta de Andaluciá (Grant FQM-195 and the Project of Excellence P11-FQM-7756), and the University of Granada for financial support. Part of this work was performed at the HFLSM, IMR, Tohoku University. I.F.D.-O. also acknowledges support by COLABS. G.R. and T.G. thank DST-SERB (Grant EMR/ 2014/00024) for funding. E.R. thanks the Generalitat de Catalunya for an ICREA Academia award.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/6/4
Y1 - 2018/6/4
N2 - Herein we report a dinuclear [(μ-mbpymNO){(tmh)3Dy}2] (1) single-molecule magnet (SMM) showing two nonequivalent DyIII centers, which was rationally prepared from the reaction of Dy(tmh)3 moieties (tmh = 2,2,6,6-tetramethyl-3,5-heptanedionate) and the asymmetric bis-bidentate bridging ligand 4-methylbipyrimidine (mbpymNO). Depending on whether the DyIII ions coordinate to the N^O or N^N bidentate donor sets, the DyIII sites present a NO7 (D2d geometry) or N2O6 (D4d) coordination sphere. As a consequence, two different thermally activated magnetic relaxation processes are observed with anisotropy barriers of 47.8 and 54.7 K. Ab initio calculations confirm the existence of two different relaxation phenomena and allow one to assign the 47.8 and 54.7 K energy barriers to the Dy(N2O6) and Dy(NO7) sites, respectively. Two mononuclear complexes, [Dy(tta)3(mbpymNO)] (2) and [Dy(tmh)3(phenNO)] (3), have also been prepared for comparative purposes. In both cases, the DyIII center shows a NO7 coordination sphere and SMM behavior is observed with Ueff values of 71.5 K (2) and 120.7 K (3). In all three cases, ab initio calculations indicate that relaxation of the magnetization takes place mainly via the first excited-state Kramers doublet through Orbach, Raman, and thermally assisted quantum-tunnelling mechanisms. Pulse magnetization measurements reveal that the dinuclear and mononuclear complexes exhibit hysteresis loops with double- and single-step structures, respectively, thus supporting their SMM behavior.
AB - Herein we report a dinuclear [(μ-mbpymNO){(tmh)3Dy}2] (1) single-molecule magnet (SMM) showing two nonequivalent DyIII centers, which was rationally prepared from the reaction of Dy(tmh)3 moieties (tmh = 2,2,6,6-tetramethyl-3,5-heptanedionate) and the asymmetric bis-bidentate bridging ligand 4-methylbipyrimidine (mbpymNO). Depending on whether the DyIII ions coordinate to the N^O or N^N bidentate donor sets, the DyIII sites present a NO7 (D2d geometry) or N2O6 (D4d) coordination sphere. As a consequence, two different thermally activated magnetic relaxation processes are observed with anisotropy barriers of 47.8 and 54.7 K. Ab initio calculations confirm the existence of two different relaxation phenomena and allow one to assign the 47.8 and 54.7 K energy barriers to the Dy(N2O6) and Dy(NO7) sites, respectively. Two mononuclear complexes, [Dy(tta)3(mbpymNO)] (2) and [Dy(tmh)3(phenNO)] (3), have also been prepared for comparative purposes. In both cases, the DyIII center shows a NO7 coordination sphere and SMM behavior is observed with Ueff values of 71.5 K (2) and 120.7 K (3). In all three cases, ab initio calculations indicate that relaxation of the magnetization takes place mainly via the first excited-state Kramers doublet through Orbach, Raman, and thermally assisted quantum-tunnelling mechanisms. Pulse magnetization measurements reveal that the dinuclear and mononuclear complexes exhibit hysteresis loops with double- and single-step structures, respectively, thus supporting their SMM behavior.
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U2 - 10.1021/acs.inorgchem.8b00427
DO - 10.1021/acs.inorgchem.8b00427
M3 - Article
C2 - 29775043
AN - SCOPUS:85048259898
VL - 57
SP - 6362
EP - 6375
JO - Inorganic Chemistry
JF - Inorganic Chemistry
SN - 0020-1669
IS - 11
ER -