Magnetic Interactions in a Series of Homodinuclear Lanthanide Complexes

Abstract

A series of seven isostructural homodinuclear lanthanide complexes are reported. The magnetic properties (ac and dc SQUID measurements) are discussed on the basis of the X-ray structural properties which show that the two lanthanide sites are structurally different. MCD spectroscopy of the dysprosium(III) and neodymium(III) complexes ([Dy(III)2(L)(OAc)4](+) and [Nd(III)2(L)(OAc)4](+)) allowed us to thoroughly analyze the ligand field, and high-frequency EPR spectroscopy of the gadolinium(III) species ([Gd(III)2(L)(OAc)4](+)) showed the importance of dipolar coupling in these systems. An extensive quantum-chemical analysis of the dysprosium(III) complex ([Dy(III)2(L)(OAc)4](+)), involving an ab initio (CASSCF) wave function, explicit spin-orbit coupling (RASSI-SO), and a ligand field analysis (Lines model and Stevens operators), is in full agreement with all experimental data (SQUID, HF-EPR, MCD) and specifically allowed us to accurately simulate the experimental χT versus T data, which therefore allowed us to establish a qualitative model for all relaxation pathways.

Dinuclear lanthanide complexes supported by a hybrid salicylaldiminato/calix[4]arene-ligand: synthesis, structure, and magnetic and luminescence properties of (HNEt3)[Ln2(HL)(L)] (Ln = SmIII, EuIII, GdIII, TbIII)

“…Such a weak antiferromagnetic coupling constant is a typical value for phenolato-bridged Gd III systems. 82,[84][85][86][87] The χ M T value of the Eu III 2 complex 5 is 2.80 cm 3 K mol −1 at 300 K, a value which is close to that expected for two non-interacting Eu III ions (2.65 cm 3 K mol −1 ), with non-negligible population of excited 7 F 1 -7 F 6 levels. The deviation from the Hund-Landé expectation value (0μ B ) is also attributable to contributions from the second order Zeeman effect in the ground 7 F 0 multiplet.…”

Correlation of Structural and Magnetic Properties in a Set of Mononuclear Lanthanide Complexes

“…The results of a full f 9 ligand field calculation are shown in Figure as a stick spectrum, indicating the upper state multiplet of the various transitions, and these calculated energies as well as the experimental energies are presented in Table S4. The Hamiltonian has been described previously, and includes electron repulsion ( F k ), spin‐orbit coupling ( ζ ), two body configuration interaction terms ( α , β , γ ), the three body parameters ( T k ), the magnetic parameters ( M k ) describing spin‐spin and spin‐other orbit interaction, and the electrostatically correlated spin‐orbit interaction ( P k ). The ligand environment is accounted for by using the Angular Overlap Model (AOM), which uses structural information about the complex and parameters that describe the weak σ and π bonding interactions.…”

“…In a balance of cost and accuracy, 7, 100, 100, and 100 states, were considered, respectively. For Dy III (4f 9 ) of the 21 sextet, 224 quartet, and 490 doublet states, all sextet, 100 quartet, and 100 doublet states were considered . Spin‐orbit coupling was introduced to the spin‐free wave functions in each case through the restricted active space state interaction method (RASSI) .…”

“…This paper serves as a continuation of our previous studies, in which we have utilized several spectroscopic and magnetometric techniques to validate our computational data . We have reported both homodinuclear lanthanide(III) and heterodinuclear 3d–4f systems, combining our computed values with alternating and direct current (ac and dc) SQUID, high frequency EPR (HF‐EPR), and magnetic circular dichroism (MCD) data, including extensive ligand field analysis based on angular overlap model (AOM) calculations ,. More recently we have utilized paramagnetic NMR spectroscopy and SQUID measurements to determine the solution and solid‐state magnetic behavior of a series of linear trinuclear Ni II 2 Ln III complexes with Ln=Y, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu .…”

Theoretically Predicted and Experimentally Observed Relaxation Pathways of two Heterodinuclear 3d‐4f Complexes

“…[13][14][15] In particular and related to our studies presented here, there is a range of reported Ni II Dy III SMMs with energy barriers and relaxation times similar to those reported herein. [16][17][18][19] We have recently prepared and experimentally studied a series of homodinuclear lanthanide and trinuclear mixed lanthanide-transition-metal complexes, [20,21] and have interpreted the experimental data with a largely established theoretical model, [5,6,[8][9][10][11][12] involving a fragmentalized approach for the CASSCF refinement of the wavefunction, with spin-orbit coupling introduced via restricted active space state interaction (RASSI-SO), and the computation of the magnetic coupling and multiplet splitting on the basis of the Lines Model and a Stevens operators scheme. The validation of this model is based on the comparison of the computed electronic parameters with a wide range of experimental magnetic and spectroscopic data, obtained from ac and dc SQUID experiments, high-frequency EPR and paramagnetic NMR spectroscopy as well as an extensive MCD study coupled with a thorough ligand field analysis.…”