Magnetic Coupling in Dinuclear Gd Complexes

Abstract

A spin density functional (SDFT) study of carboxylate-bridged and diazenido-bridged dinuclear gadolinium compounds is presented. Calculated magnetic coupling constants for the carboxylate-bridged structures are in good agreement with experimental data, confirming the ability of the broken symmetry approach used in this work to predict magnetic behavior in such compounds. The systematic trend wherein symmetrically bridged complexes are antiferromagnetically coupled and asymmetrically bridged are ferromagnetically coupled is reproduced by the SDFT calculations. The mechanism underlying magnetic coupling in closed- and open-shell dinuclear complexes is described using a perturbative molecular orbital model that focuses the influence of the 4f(7)-5d exchange interaction on molecular orbitals with significant 5d-orbital character for the complex [[[(Me(3)Si)(2)N](2)(thf)Gd](2)(N(2))]. Open-shell electronic configurations facilitate strong ferromagnetic coupling, whereas in closed-shell systems antiferromagnetic coupling is usually preferred.

Using the Singly Deprotonated Triethanolamine to Prepare Dinuclear Lanthanide(III) Complexes: Synthesis, Structural Characterization and Magnetic Studies

“…In the case of 2, the {Gd 2 III (µ 2 -OR) 2 (1) • . Thus, the antiferromagnetic Gd III ···Gd III exchange interaction in 2 is in accordance with the theoretical predictions [20].…”

“…In the case of 2, the {Gd2 III (μ2-OR)2} 4+ core shows near-D2h symmetry; the Gd-(μ2-OR) bond distances are nearly equal (2.258(1) and 2.303(1) Å) and the C-(μ2-Ο)-Gd angles are in the relatively narrow range 119.3(1)-130.5(1)°. Thus, the antiferromagnetic Gd III •••Gd III exchange interaction in 2 is in accordance with the theoretical predictions [20]. and Ho III ( 5 I8, S = 2, L = 6, gj = 5/4) centers respectively.…”

“…This J value is typical for dinuclear complexes containing the {Gd III 2(μ2-OR)2} 4+ core [17,18,20,25,50]. Rov and Hughbanks performed a spin density functional (SDFT) study of dinuclear Gd III complexes containing the {Gd2(μ2-OR)2} 4+ core [20]. The systematic study showed that symmetrically bridged complexes are antiferromagnetically coupled and asymmetrically bridged ones are ferromagnetically coupled.…”

“…As expected for pure Ln III systems, the exchange interaction is rather weak as a consequence of the shielded 4f orbitals that have small overlap with bridging ligand orbitals. This J value is typical for dinuclear complexes containing the {Gd III 2(μ2-OR)2} 4+ core [17,18,20,25,50]. Rov and Hughbanks performed a spin density functional (SDFT) study of dinuclear Gd III complexes containing the {Gd2(μ2-OR)2} 4+ core [20].…”

“…More importantly, dinuclear Ln III SMMs are very important model systems to answer basic questions regarding single-ion relaxation vs. slow magnetic relaxation arising from the molecule as an entity. Thus, Ln III 2 complexes are highly desirable [10][11][12][13][14][15][16][17][18][19][20]. Another interesting area to which dinuclear lanthanide(III) complexes (and also mononuclear ones) are relevant is quantum computation; Ln III ions are promising candidates for encoding quantum information [21,22].…”